STScI Newsletter December 1994


HST SCIENCE
HIGHLIGHTS

COMETS SMASH INTO JUPITER
After more than a year of anticipation, comet P/Shoemaker-Levy 9 (SL9) finally made its
cataclysmic plunge into Jupiter=D5s atmosphere during 16-22 July 1994. Virtually every
observatory in the world took a look at Jupiter that week and few, if any, were
disappointed in the results. The spectacular fireballs and plumes rising off the limb of
Jupiter   (Fig. 1), and the subsequent production of huge impact scars on the planet      
(Fig. 2) thrilled professional and amateur astronomers alike. The SL9-Jupiter impact was
the first opportunity in recorded history to predict and witness the collision of two solar
system bodies, and a wealth of data were obtained that hopefully will lead to a better
understanding of how such events shaped (and continue to shape) the evolution of our
planetary system.
The HST was in the middle of the excitement due to its superior spatial resolution and UV
coverage. A major HST observing campaign (~120 orbits total) was started in January of
1994 and continued until late August. (Jupiter entered solar avoidance during the first week
of September.) There were six principal scientific investigations: imaging and spectroscopy
of SL9 prior to impact (PI: Hal Weaver, STScI), optical and near-UV WFPC-2 imaging of
Jupiter (PI: Heidi Hammel, MIT), WFPC-2 imaging study of stratospheric hazes on Jupiter
(PI: Bob West, JPL), UV imaging of Jupiter (PI: John Clarke, Univ. of Michigan), Jovian
UV spectroscopy (PI: Keith Noll, STScI), and magnetospheric studies (PI: Melissa
McGrath, STScI). A total of over 70 scientists participated in these 
investigations as co-Is.
Prior to the impacts, no one was sure that any effects of the collisions would be
observable. Most of the uncertainty was due to our inability to gauge the sizes of the
impacting bodies to better than a factor of ten, which translated into a factor of 1000
uncertainty in the impact energy. Some of the early estimates for the sizes were as large as
~15 km in diameter, which would result in    ~3 =B4 1031 ergs       (== 8 =B4 108 MTons TNT)
of energy input into Jupiter. The HST observations demonstrated clearly that the nuclei in
SL9 were not nearly that big; the HST upper limits were ~4 km for the larger nuclei
corresponding to an energy dump of 6 =B4 1029 ergs (==107 MTons TNT). However, since,
in the most conservative interpretation, the HST observations yielded only upper limits to
the sizes, the energy associated with each collision could possibly be much less. Despite
the huge explosions observed during July, at the time of this writing there is still
considerable uncertainty as to the actual sizes of the fragments of S
L9.
The parent body of SL9 was incredibly tenuous with a tensile strength of only ~3000 dyne
cm-2 (==0.003 bar), or smaller. Apparently the remaining fragments were similarly only
very weakly bound because they continued fragmenting well after the tidal disruption of the
original body. Figure 3 shows the temporal evolution of one of the most interesting regions
of SL9, the P-Q complex, in which both the P and Q nuclei apparently fragmented further.
The nuclei broke into separate, individual chunks indicating that there was a dominant body
at the core of each coma and not just a =D2swarm=D3 of thousands of objects all having roughly
the same (much smaller) size.
There has been a raging debate regarding the nature of SL9: was it a comet or was it an
asteroid that was improperly named? This question is not simply an exercise in categorizing
SL9 because we would like to know whether SL9 was captured by Jupiter from the
asteroid belt, or if SL9 came through the inner solar system on a typical cometary orbit.
Also, we know that SL9 was extremely fragile, and proving that SL9 was an asteroid
would demonstrate that asteroids can be as tenuously bound as comets. However, we must
recognize that the distinction between comets (which are usually icy bodies) and asteroids
(which are usually relatively devoid of ice) becomes blurred when discussing objects that
formed in the trans-Jovian region. Having said that, there have been no spectroscopic data
that clearly show SL9 to be an icy body. No typical cometary molecular emissions were
observed near SL9, but at 5 AU such emissions are difficult to produce. On 14 July 1994
there was a spectral outburst in which MgII emission near 2800 =81 was observed, but Mg is
an important constituent of both comets and asteroids. The MgII outburst, and the
reddening of the dust continuum that followed shortly thereafter, may have been produced
by the charging and subsequent explosion of small grains as SL9 passed from
interplanetary space into the Jovian magnetosphere.
Although there are still many unresolved questions regarding SL9, there is no doubt that it
made its mark on Jupiter (Figs. 1 & 2). Fifteen of the SL9 nuclei produced detectable
impact sites, while five left no discernible disturbance. The largest and freshest impact sites
displayed the same morphology: crescent-shaped ejecta (with rays associated with the G
impact site), one or more atmospheric waves, and an asymmetric central disturbance. For
the G site, the outer edge of the crescent was ~13,000 km from the apparent entry site. The
ejecta patterns and the plume heights (above Jupiter=D5s limb) suggest that the plume material
had a vertical velocity of ~10 km s-1 independent of explosion energy. Images of the large
impact sites during the first 3 hours after impact showed transient =D2ring=D3 phenomena that
were most likely caused by atmospheric waves moving with a speed of ~400-500 m s-1.
The temporal evolution of the impact sites was monitored for a little more than a month,
during which time the impact-created clouds faded in contrast and spread in both longitude
(primarily) and latitude. Although individual impact sites may be difficult to see next year,
there will probably be long-term effects on Jupiter=D5s atmosphere due to the long residence
times of aerosols created by the impacts. (Remember how long we had beautiful sunsets on
Earth following the eruption of the Mt. Pinatubo volcano?) Measurements of the latitudinal
extent of the aerosol haze next year should provide extremely valuable information on the
nature of the meridional circulation in Jupiter=D5s stratosphere, which cannot be studied in
any other way.
Several interesting conclusions can be drawn from a detailed photometric analysis of the
HST WFPC-2 images. First, the total volume of impact debris aerosol after July 22 was
approximately equal to the volume of a 1 km diameter sphere. Second, the most promising
compositional candidate for the impact debris is an organic material rich in sulfur and
nitrogen (Fig. 4). A Jovian atmosphere origin for the debris is indicated if a single material
was responsible for both the transient aerosol traced in the wave features and the long-lived
aerosol debris pattern. Third, the particle mean radius is in the range 0.15-0.3 microns,
with a clear evolution from 0.21 to 0.28 microns between 23 July and 24 August due to
coagulation with little loss from sedimentation. Finally, in the dense core regions particles
extend over many scale heights from ~ 1 mb to 200 mb or deeper.
The WFPC-2 and FOC were used to image Jupiter at far-UV (FUV) wavelengths (l < 2100
Angstroms) in order to study the response of Jupiter=D5s upper atmosphere to the impacts,
measure upper atmospheric winds through the observed motions of impact-related
absorbers, and search for auroral emissions associated with SL9. In the FUV images the
impact regions were considerably darker, covered a larger region, and were more diffuse
with less central contrast than at longer wavelengths. The impact sites also clearly darkened
in the FUV over a 2-3 hour period post-impact. Although the impact feature centers
generally remain fixed in system III longitude (the longitude system based on Jupiter=D5s
magnetic field geometry), the initial dispersions of FUV absorbing material in the G, L,
and K sites showed pronounced north-south extensions, with initial speeds of ~1 km s-1.
Transient northern auroral emissions were detected at unusually low magnetic latitudes just
after the K impact, with similar but fainter emissions at either side of the K impact in the
southern hemisphere. The northern emissions appeared to fall near the magnetic conjugate
of the K impact site and may be associated with the transport of charged particles from the
impact site to the northern hemisphere along magnetic field lines (Fi
g. 5).
The composition of Jupiter=D5s stratosphere and upper troposphere was dramatically altered
by the impacts of SL9. UV spectra obtained with the FOS showed absorptions from at least
ten molecules in the vicinity of the impact sites, most never before observed in Jupiter (Fig.
6). The large mass of sulfur-containing material, more than 1014 grams in diatomic sulfur
(S2) alone and including CS2, CS, H2S, and S+, indicates that much of this material was
derived from Jovian sulfur-bearing material, unless the impacting nuclei were several km in
diameter. If the sulfur-bearing material was primarily of Jovian origin, this would be the
first observation of any sulfur compound in Jupiter, providing an important confirmation of
models of cloud composition and a possible source of cloud coloration. The presence of
Jovian sulfur and stratospheric ammonia (also observed by HST) argues that the impactors
reached at least the 1-2 bar level in Jupiter=D5s atmosphere. Neutral and ionized metals were
observed in emission, including MgII, MgI, SiI, FeI, and FeII, and all of these certainly
were brought to Jupiter by the impactors. The mass required in metals is easily derived
=66rom a modest-sized impactor. Oxygen-containing molecules were conspicuous by their
absence in the HST GHRS spectra, with the exception of absorption that could possibly be
due to water. Significant upper limits were derived for SO2, SO, and 
CO.
The HST also made spectroscopic observations (using the FOS and GHRS) of the Io torus
during the impact week. No new emission features were detected, particularly from Si and
C, which would have been indicative of the presence of SL9 dust within the torus. There
were some changes in the normal torus emissions during the impact week, but these were
generally well within the range of variability observed over the past 12 years prior to the
SL9-Jupiter encounter.
As you can see from the discussion above, there was a rich harvest of scientific results
=66rom the HST SL9-Jupiter impact campaign. However, the implications of these data are
far from being completely understood and will continue to occupy the planetary community
for quite some time. Definitive answers have still not been found for such basic questions
as: the sizes of the SL9 nuclei, the depth of their penetration into the Jovian atmosphere,
and the source of the material in the impact sites. To address these unresolved issues, the
STScI and Johns Hopkins University are jointly hosting IAU Colloquium 156 (this will
also be the STScI spring workshop) during 9-12 May 1995 in Baltimore. See the meeting
announcement later in this Newsletter for further information. The initial results from the
HST Comet-Jupiter campaign will be published in Science in February.

=D1 Hal Weaver (STScI)
John Clarke (Univ. of Michigan)
Heidi Hammel (MIT)
Melissa McGrath (STScI)
Keith Noll (STScI)
and Bob West (JPL)

for the HST comet-Jupiter impact campaign investigators

THE HST KEY PROJECT ON THE EXTRAGALACTIC DISTANCE SCALE
Accurate distances are critical for determining the present rate of expansion of the universe,
or the Hubble constant, H0. The lack of an accurate value for H0 has frustrated attempts to
determine the expansion timescale and scale size of the universe and to provide constraints
on cosmological models, the density of baryons produced in the early universe, the amount
of dark matter, and formation models for large-scale structure in the universe. The aim of
the Key Project is to provide a value of H0 that is accurate to 10%. The primary goal of the
program is to measure Cepheid distances to a sample of about 20 galaxies located in the
field and in small groups. A secondary and more difficult goal is the discovery of Cepheids
and measurement of the distances to the Virgo and Fornax clusters.
As part of the Early Release Observations (ERO), BVR images of a field in M100 (reported
in the STScI Newsletter, Vol. 11, No. 1, April 1994) showed the feasibility of discovering
Cepheids in this Virgo cluster galaxy. Based on this success, Bob Williams enthusiastically
supported moving up the observations of M100 to the spring of 1994. A sequence of
observations began in April 1994 covering a 60-day window. The spacing of the
observations was optimized for the discovery of Cepheids having periods ranging from 10
to 60 days.
The discovery of 20 Cepheids in M100 has just recently been reported by Freedman et al.
(Nature, v. 371, p. 757, 27 October 1994 issue). The V and I period-luminosity relations
for these Cepheids are shown in Figures 7 and 8. The M100 Cepheids are represented by
open circles and the calibrating Large Magellanic Cloud Cepheids are denoted by solid
dots. Measurement of the apparent distance moduli at V and I with respect to the Large
Magellanic Cloud yields a true distance (corrected for interstellar reddening) of 17.1 Mpc
+- 1.8 Mpc. At present the large uncertainty is due to the Cepheid zero point calibration and
the reddening determination.
To determine the Hubble constant from the distance of M100, the question of where M100
lies with respect to the core of the Virgo cluster needs to be addressed. We have allowed
for the back-to-front depth of the cluster given by the observed distribution of spirals and
conservatively adopt an uncertainty of +- 20% for the mean distance to the Virgo cluster.
Adopting a cosmological recession velocity of Virgo of 1404 km s-1 yields a value of H0 ==
82 +- 17 km s-1 Mpc-1. Based on a range of published Coma-Virgo relative distances, we
find a value of H0 == 77 +- 16 km s-1 Mpc-1 at the distance of the Coma Cluster. We
conclude that a value of H0 ~ 80 km s-1 Mpc-1 holds out to distances 
of about 100 Mpc.
A value of H0 == 80 +- 17 km s-1 Mpc-1 is consistent with a low-density (0.1 < W < 0.3)
universe and t0 == 12 Gyr. However, for the standard Einstein-de Sitter model (W == 1, L ==
0) t0 == 2/3 Ho-1 == 8 Gyrs, which is below the current stellar evolution age estimates for
globular clusters (14 +- 2 Gyr) in addition to other age estimates. These results underscore
the need to reduce the uncertainties in the value of H0 and the other
 age estimates.
Future plans for the Key Project include the calibration of 5-6 secondary distance
determination methods using galaxies in the field and in small groups. These secondary
methods can be used to measure the distances to galaxies well beyond 
the Virgo cluster
where peculiar velocities are a much smaller fraction of the cosmological velocity. In
addition, in Cycle 5 we plan on searching for Cepheids in the southern hemisphere cluster
Fornax, a cluster more compact than the Virgo cluster but at a comparable distance. These
data will allow a direct means of assessing the systematic errors in the current extragalactic
distance scale and allow a determination of the Hubble constant to unprecedented accuracy.
The success at finding Cepheids in the Virgo cluster suggests that a measurement of H0 to
an accuracy of 10% is now a feasible goal using the Hubble Space tele
scope.

=D1 Wendy Freedman
(Carnegie Observatories)

Galaxies at High Redshift
The refurbished HST is a powerful new tool for investigating galaxies at cosmological
distances, providing imaging with kiloparsec-scale resolution at all redshifts. A variety of
HST programs are exploiting this capability, seeking to learn how and when galaxies
formed and what processes have shaped their histories. Rich clusters of galaxies have
served as a valuable laboratory for such research, and indeed it was in distant clusters that
the first clear evidence for evolution was observed with the discovery of an increasingly
numerous population of blue galaxies in high redshift clusters (e.g., Butcher and Oemler
1978, 1984). HST observations have shown that the blue galaxies in clusters at z~0.4 are
mostly spirals, often with signs of morphological disturbance which may provide clues
about their disappearance by the present epoch (e.g., Dressler et al. 1994, Couch et al.
1994). At the same time, the elliptical galaxies (which dominate clusters today) appear
normal,     with little evidence for dramatic changes in their spectral or morphological      
properties.
Observations of still more distant clusters let us trace this evolution to earlier epochs. In
Cycle 4, we have used HST and WFPC-2 to image a cluster near the radio galaxy 3C 324
at z==1.206     (Fig. 9). The field was selected from a ground-based infrared survey of the
environments of high redshift radio galaxies, and is notable for its population of very red
galaxies =D1 objects with colors little different from those of present-day elliptical galaxies
redshifted to z==1.2 with minimal spectral evolution. At this large redshift, the cluster
galaxies are extremely faint, requiring long exposures to permit morphological
classification and surface photometry. HST observed the 3C 324 field for 32 orbits,
exposing for a total of 18 hours through the F702W filter. The resulting image contains
literally thousands of faint galaxies down to the detection limit R~29. Many of these may
well be foreground or background to the cluster, as we are peering through a tremendous
volume of the universe to reach 3C 324. However, in the central regions where the density
of galaxies is highest, many objects are likely to be cluster members.
The red galaxies are, with few exceptions, remarkably unremarkable. They have simple
spheroidal morphologies and surface brightness profiles well fit by r1/4 laws. In short,
their relaxed appearance and red colors indicate that these are quite ordinary E/S0 galaxies.
This has immediate cosmological implications, since the universe must have been old
enough at z==1.2 to accommodate them. Cosmologies with high values for the Hubble
constant leave little time for these galaxies to form and evolve to m
aturity by that redshift.
Among the bluer galaxies, a bewildering variety of morphologies is apparent. Redshifts are
not yet available, and on a case-by-case basis it is not possible to definitively assign cluster
membership. Very few galaxies are recognizable as normal spirals, although some
elongated objects may be edge-on disks. There are many highly irregular galaxies, objects
with =D2tadpole-like=D3 head-tail morphologies, disturbed and apparently merging systems, and
a multitude of faint, tiny shards and fragments of indeterminate nature. Many extremely
faint, barely resolved galaxies are present: these could be dwarf galaxies in the cluster, or
perhaps some as yet unknown field population. While it may appear from these images that
the high redshift universe (apart from the ellipticals) was a strange and unfamiliar place, it
should be remembered that for z > 1 HST observes in the rest frame ultraviolet, where star
formation can most dramatically affect observed morphologies. Cosmological surface
brightness dimming is also very strong, and may also bias our visual impressions.
Nevertheless, it is difficult to escape the impression that the evolutionary processes shaping
(or disrupting) disk galaxies in clusters at z==0.4 were working overtime at z==1.2.
The morphology of the radio galaxy itself is genuinely bizarre. 3C 324 is a classic example
of the =D2alignment effect,=D3 the tendency for the optical (i.e., rest frame UV) light in high
redshift radio galaxies to align with the radio source axis. The physics behind this
alignment is a subject of vigorous debate. Star formation triggered by the passage of the
radio source jet has been a popular model, but detections of strong polarization in many
radio galaxies (18% for 3C 324) suggests that scattered light, perhaps from the otherwise
hidden active nucleus, could play a dominant role. At HST resolution, 3C 324 breaks up
into a long, thin stream of high surface brightness clumps, each as luminous as an ordinary
galaxy in its own right. Although the structure is roughly aligned with the radio source,
there is little point-by-point correspondence between radio and optical features, arguing
against synchrotron or inverse Compton origins for the UV light. The optical structure may
be due to reflected light from the AGN, but it does not show a biconical morphology (e.g.,
like that seen in Seyfert galaxy ionization cones). The scattering medium must itself be
anisotropically clumped to produce such compact, bright knots. If, instead, we are seeing
star formation, the reported polarization remains unexplained.
These images, as well as others recently obtained by other groups, are giving us our first
high-resolution view of the distant universe. Moreover, the long exposures reach
remarkably deep limiting magnitudes, thanks in part to the dark background and to the
extreme compactness of many of the faint galaxies. The potential for surprises and new
discoveries is high, and careful analysis during the upcoming months may reveal new
features of the high redshift universe unsuspected from the ground-ba
sed observations.

=D1 Mark Dickinson (STScI),
Hyron Spinrad and Arjun Dey
(UC Berkeley),
S. Adam Stanford (IPAC/JPL),
Peter Eisenhardt (JPL),
and George Djorgovski (Caltech)

FOS OBSERVATIONS IN THE CORE OF THE galactic STARBURST NGC 3603
NGC 3603 is the densest, most massive visible starburst region in our galaxy. It is in many
respects analogous to the giant H II regions seen in external galaxies, such as 30 Doradus
in the LMC or NGC 604 in M33. However, because of the large extinction it suffers
(Av==4.6 mag), and because of its very high density, the stellar content of NGC 3603 is
rather poorly known.
Cycle 1 WFPC-1 images (Moffat et al., Ap. J., v. 436, p. 183, 1994) revealed remarkable
similarities between NGC 3603 and R136, the core of 30 Dor. In particular, the projected
star density for stars brighter than Mv==-5.0 in both objects increases inwards with a
power-law of slope -1.8; the central star density in NGC 3603 is even slightly higher than
that found in R136. Even the integrated spectra of both objects are very similar, showing
strong emission lines characteristic of Wolf-Rayet stars, and absorption lines typical of
early-type O stars.
In order to probe the stellar content of the inner core of NGC 3603, we (Drissen, Moffat,
Walborn, Shara) have obtained spectra of 14 stars within 4" of the cluster center with the
FOS+COSTAR in early September; the G400H grating and the 0.26" aperture were used.
The three brightest stars in the cluster (labeled A1, with Mb==-7.8; B, Mb==-7.8 and C,
Mb==-7.3) are found to be late-type (WN6) Wolf-Rayet stars. Their spectra (Fig. 10) show
that hydrogen is still present in their outer layers, suggesting that these stars have just
recently evolved away from the main sequence. Moreover, six O3 stars (thought to be the
most massive stars known) are also found within the inner 3" (0.1 par
sec).
Such a dense concentration of early-type massive stars is unique in our galaxy. A detailed
study of the stellar content of NGC 3603 is feasible with HST and will help us understand
more distant, unresolved starbursts.

=D1 Laurent Drissen (STScI)


THE HST OBSERVATORY
DIRECTOR=D5S PERSPECTIVE
As the anniversary of the First Servicing Mission approaches, we are again struck by the
remarkable success of that mission and its importance for astronomy and the future of
HST. The optical corrections and new instruments and components have continued to work
well and have yielded a cornucopia of new images and scientific breakthroughs. The
discovery of a rapidly rotating gas disk in the center of M87 and the implied mass at the
center of this active galaxy has confirmed the hypothesis that many galaxies may harbor
massive black holes in their cores. The remarkable images of the Comet P/Shoemaker-Levy
9 impact sites on Jupiter (see the article by Weaver et al. in this Newsletter), together with
the wealth of coordinated ground-based observations, captured the imagination of the
world in July and provided a rich astronomical database for further study. And the release
of the first observations of Cepheid variables in the Virgo Cluster (see the article by
Freedman in this Newsletter) was an auspicious beginning of the Key Project to determine
the Hubble Constant. Any of these successes could be considered the crowning
achievement of a research career. Yet, we believe that these only suggest the potential of the
HST for exciting, forefront science in the coming decade.
Perhaps the most enthralling image we have seen is a WFPC-2 observation of the cluster of
galaxies surrounding the radio galaxy 3C 324 at z == 1.21 (see the article by Dickinson et al.
in this Newsletter). Requiring more than 30 orbits of HST observing, we believe that this
is the deepest image obtained by the optically-corrected HST. The image reveals a
population of =D2spheroidal=D3 galaxies, which appear to be fully relaxed, and a larger
population of complex, often linear structures. None of these latter =D2galaxies=D3 appears
similar to typical spirals at z==0. The 0.1 arcsec resolution of HST appears to just resolve
many of these spheroids and amoeba-like structures. At face value, these results suggest
that many galaxies are undergoing significant evolution at this redshift, while others must
have been formed at significantly earlier epochs. We are very excited not only by the
spectacular data but also by the implication that HST=D5s resolution and sensitivity are
uniquely capable of studying this important epoch of galaxy formation. To this end, we are
considering using Director=D5s Discretionary time to facilitate such studies in Cycle 5 (see the
accompanying special article on our plans).
The Telescope Allocation Committee (TAC) recently convened to make its
recommendations for the General Observer program in Cycle 5. Eight subdiscipline panels
reviewed and ranked over 850 proposals for GO and Archival Research programs.
Fortunately, the predicted higher efficiency of spacecraft operations will provide a record
number of orbits for GOs beginning in the summer of 1995, about 3,400. Since the
requested number of orbits is approximately 14,250, or four times larger, the TAC=D5s job
was a little easier this year. We convey our gratitude to the many panel and TAC members
who sacrificed their most precious resource-time-to play a vital role in the definition of the
HST science program. The programs that have been approved for Cycle 5 are listed in an
accompanying Newsletter article. We extend our congratulations to all the successful Cycle
5 proposers and encourage the others to try again next cycle.
As the portion of HST time allocated to GOs has increased in Cycle 5, we have begun to
work with the original Investigation Definition Teams (IDTs or GTOs- the Guaranteed
Time Observers) on the completion of their programs in Cycle 5. These investigators were
selected following the 1977 Announcement of Opportunity and have provided scientific
leadership to the HST Program since its inception. Most of the early science done with
HST, and the recent Early Release Observations made after the servicing mission, were
part of the IDT science programs. In many ways, these science programs have literally
defined the HST Observatory, its operation, and its success. After the completion of the
IDT science programs in Cycle 5, we look forward to continuing our relationship with the
IDT members as HST General Observers.
Progress continues on the Space Telescope Imaging Spectrograph (STIS)
 and the Near-
Infrared Camera and Multi-Objective Spectrograph (NICMOS) in preparation for their
installation in HST during 1997. At the STScI, we have appointed a Servicing Mission =D597
science team, with Chris Blades as the team leader, to work with the two science teams at
GSFC and Steward Observatory in the areas of operational modes, calibration strategies,
and pipeline reductions. Both instruments will bring dramatic, new capabilities to the HST
and new challenges in terms of 2-D calibrations. It is our goal to smoothly integrate the
efforts of the science teams and the STScI such that the science commissioning and early
release period following the 1997 servicing mission is as flawless and expeditious as after
the installation of COSTAR and WFPC-2.
Several other technical accomplishments made in the last six months are particularly
noteworthy. First, Side 1 of the GHRS was made fully operational and re-calibrated. Many
Cycle 4 GO and GTO programs are now enjoying the high UV sensitivity of the Side 1
detector and the highest resolution spectroscopic capabilities that Side 1 provides. The
spring Newsletter (v. 11, no. 1, April 1994) described the Hubble Data Archive (HDA)
and the new StarView user interface. The final milestone of the HDA development was met
this October when the Data Archive and Distribution System (DADS) became fully
operational, allowing us to turn off the prototype Data Management Facility (DMF). All
previous HST data have been reformatted onto higher density optical disks and are
accessible from DADS via StarView. Finally, we congratulate the members of the PRESTO
initiative for streamlining the planning and scheduling system and for exceeding their initial
goals: the new LaTeX- based format was used successfully for the Cycle 5 proposal
submissions, and the spacecraft is currently being operated at approximately 45%
scheduling efficiency. Cycle 5 observers will utilize a new, more interactive system for
planning their observations, the Remote Proposal System 2 (RPS2). We think that most
users will appreciate the new orbit-based planning system as one which puts the
astronomer in charge of maximizing the science programs. The PRESTO team has set a
goal of regularly exceeding 50% planning efficiency in Cycle 5. We have every confidence
that they can do it!
Finally, some sober reflections. As mentioned in the last Newsletter, the HST Project and
most other NASA astrophysics missions have been under intense budgetary pressure. This
summer, the STScI completed a reduction-in-force program which decreased the resources
supporting HST operations by approximately 60 people=D1 a 15% reduction. Generally, we
have had to take greater risks in the maintenance of systems and software, as well as
general belt-tightening. We will work hard to reduce the impact on the HST observers, but
we have had to eliminate some specific capabilities and support. As of January, we will
have no regularly scheduled real-time monitoring of HST data. We will retain the ability to
do real-time target acquisitions, but unforeseen, last-minute heroics to save observations
will be almost impossible. We have also eliminated user assistance for the FGS, given its
low usage and mostly then by the Astrometry Science Team. (FGS proposals are still
supported.) During this year, we will begin to reduce the support of current instrument
calibrations in favor of preparing for the new instruments, STIS and NICMOS, in 1997.
These steps have been taken in consultation with NASA, the Space Telescope Institute
Council, and the ST Users Committee, and are the result of many reviews of priorities and
future directions for the STScI and NASA. As the ST Users Committee report indicates
(see the accompanying article by Lauer), the reductions have been felt throughout the
Project and have created significant risks, particularly for future instruments and
Observatory maintenance. Nevertheless, we remain optimistic that the HST Observatory
can be maintained at the forefront of astronomy throughout the decade and, with the
installation of an Advanced Camera in 1999, well into the next centur
y.

=D1 Bob Williams (Director)
and Peter Stockman (Deputy Director)

HST CYCLE 5 DIRECTOR=D5S DISCRETIONARY TIME
By agreement with NASA, the STScI Director may allocate a certain fraction of time on
HST at his/her own discretion. For Cycle 5 this amounts to more than 250 orbits.
Director=D5s Discretionary (DD) time has usually been allocated in small amounts to a number
of individual PIs throughout each cycle in response to specific requests for new or urgent
observations, although it could in principle be assigned to a few large projects. Because of
the possibility that a large allotment of time could make an important difference to some
fundamental problem in astronomy, I wish to consider this latter alternative for the
assignment of DD time in Cycle 5, to take full advantage of HST=D5s current superb
performance.
Of all the impressive data that I have seen from the refurbished telescope, covering a wide
range of topics, I have personally found the imaging of distant galaxies to be the most
exciting and significant. It is evident that HST is already revealing how galaxies may form
and evolve, contributing in a profound way to this important problem. I am therefore
considering allocating a significant fraction of the Cycle 5 DD time to the topic =D4The
Formation and Evolution of Galaxies.=D5 Some of this time may be assigned to certain of the
proposals submitted to the Cycle 5 TAC which did not receive a full allotment of the time
requested, but the bulk of the time would be given to one or two large groups which
specifically propose for it. I will of course keep a certain fraction of the DD time in reserve
for unexpected contingencies during the cycle. I intend to convene an informal advisory
group to consider with me the most useful types of HST programs addressing the evolution
of galaxies, including the best way in which we might coordinate HST programs with
those on other telescopes (ground-based or satellite). If I am convinced that a substantial
impact can be made to this subject by the allocation of the order of 150-200 additional
orbits, over and above the Cycle 5 TAC recommendations in this area, I will consider (1)
issuing a call for proposals from groups who wish to be considered for the allocation of a
large fraction of this time, assigning the bulk of the time to one or two groups who will
function as a coordinated team and bring to bear a wide range of resources on the subject,
and (2) augmenting proposals in this area which were recommended by the Cycle 5 TAC
but which, due to proposal pressure, were reduced in their scope.

=D1 Bob Williams (Director)

RESIGNATION OF PETER STOCKMAN AS DEPUTY DIRECTOR
It is with real regret that I announce the resignation of Peter Stockman as Deputy Director
of the Institute, effective 1 June 1995. Peter has served superbly as Deputy and Acting
Director for almost seven years, helping usher the Institute through important changes from
its pre-launch development focus through the problems of spherical aberration, to an
organization that has been able to concentrate on the acquisition, calibration, and disbursal
of superb data. Peter=D5s affability and consummate integrity and his thorough technical
understanding of so many aspects of the HST is a rare mixture which has been of great
importance to the Project.
Peter can take pride in many real accomplishments during his tenure in the Director=D5s
Office, ranging over scientific, personnel, technical, budgetary, and political matters. For
some time now he has wanted to spend more time on his own personal research and on
new Institute initiatives, but has been unable to do so because of the constant pressure of
his managerial responsibilities. He has continued to serve as my right hand man during the
past year while I have been coming up to speed at the Institute. With Cycle 4 and
preparations for the 1997 servicing mission well underway, he has decided this is the
appropriate time to make the change that he has wished, returning to a position within the
Institute that will keep him in the thick of things, but not so over-committed that he cannot
spend adequate time on research and projects that interest him.
Peter wishes to remain associated with the Institute as a scientific staff member, working
on projects that require technical expertise. He is particularly interested in devoting himself
to getting the Institute involved in new initiatives. Since this is vital to the future of the
Institute, I am pleased that we will have Peter to rely on in this ar
ea.
The search for a new Deputy Director will commence immediately. The position requires
explicit NASA approval in addition to that of AURA. I have been authorized by the Space
Telescope Institute Council (STIC) to conduct the search, which will be done via an
independent Search Committee that I am constituting and that will report to me. Members
of this committee will come from the STIC, the Institute scientific staff, and the broader
astronomical community. I am pleased to say that Dr. Garth Illingworth has agreed to Chair
the committee.

=D1 Bob Williams (Director)

HST SPACECRAFT STATUS
HST operations have been extremely smooth in the year since the first servicing mission.
The hardware installed during the first servicing mission has been performing as expected.
As a result, all the observing restrictions imposed in the year or so before the servicing
mission have been lifted.
The final first servicing mission improvement is related to the new Solar Arrays. The
original Solar Arrays had no thermal blankets on the thin metal tubes, called bistems, which
held them extended. As a result, they underwent substantial bending as the HST went
between full sunlight and darkness conditions. This bending imparted a substantial pointing
jitter to the telescope line of sight. During the period between launch and the first servicing
mission, a number of flight software changes were made to mitigate this jitter. The final
version of this software, called SAGA-II, employed a filtering technique in the vehicle
control law. This version of the software reduced the jitter to an acceptable level. The new
Solar Arrays installed during the servicing mission had a number of design changes,
including thermal blankets on the bistems. These changes substantially reduced the
mechanical jitter input to the HST during day/night transitions. The design changes also
resulted in a different frequency response for the Solar Arrays. The SAGA-II software was
disabled after the servicing mission, until the frequency response of the new Arrays could
be measured in orbit and the stability of the SAGA-II with the new Arrays could be
demonstrated. The new arrays, without the SAGA-II filtering, did still induce noticeable
jitter in the line of sight of the telescope. The SAGA-II was proven to be stable with the
new Arrays and was activated in June. The combination of the new Arra
ys with the SAGA-
II filtering reduces the jitter to a negligible level. The RMS jitter during 60 second intervals
is now typically 2-3 milliarcseconds in each axis, with values of 4-5 milli-arcseconds
during day/night terminator crossings.
HST had another holiday weekend safemode entry, on July 3. (Safemodes seem to occur
preferentially near holidays.) This safemode was caused by the failure of the third DF-224
computer memory. The symptoms of this failure were very similar to the symptoms of the
two previous memory failures, so it is believed that the same basic mechanism is the cause.
This memory board was de-activated and the contents were switched to 
one of the co-
processor shared memory units. The co-processor, installed during the first servicing
mission, contains shared memory units which can be accessed and used 
either by the DF-
224 or the co-processor microprocessor. This was the first regular use of the co-processor
since it=D5s installation. The co-processor memory is working fine, so in early December we
will transfer operations from two of the three remaining active DF-22
4 memories to the co-
processor. The last DF-224 memory will stay active until another unrelated safing gives us
the opportunity to change it also (it is not possible to switch the last memory without
causing a safing, so we will wait for a =D2natural=D3 safing rather t
han inducing one). The DF-
224 memories will be shut off and kept as spares. The co-processor has 8 shared memory
units, of which only 4 are needed, so there are plenty of spares.

=D1 Rodger Doxsey (STScI)


SCIENTIFIC
INSTRUMENTS
FAINT OBJECT CAMERA INSTRUMENT NEWS
The f/96 relay of the FOC continues to work well in combination with COSTAR and we
continue to see the same level of performance reported in the previou
s Newsletter.
In addition to the routine F/96 calibration activities, we have also succeeded in switching on
successfully the F/48 relay on 31 October 1994, 08:54 UT, to execute a calibration
program aimed to characterize the performances of the detector, which had been last
activated before the COSTAR installment (December 1993). The HV was turned on via the
modified ramp sequence, and the initial warm-up time of 75 minutes was waived to
maximize the useful working time of the instrument. The results are encouraging and very
different from the previous switch-on (December 1993), in which the F/48 had been
successfully activated and had remained on for three hours (in addition to the 75 minutes
warm-up time), but had showed an increased background level which reached saturation
less than 2 hrs after the first image. The behavior is different this time, showing a
background decreasing with time. The F/48 was then switched off after approximately 5
hrs of observation. More detailed tests are being now planned to establish the repeatability
of this result.

Point Spread Function
We have found the alignment of COSTAR with the FOC to be very stable and the quality of
the FOC Point Spread Functions (PSFs) to remain excellent with the one exception of
focus drifts. Due to its sampling characteristics (the FOC is the only instrument on board
the HST which critically samples the telescope=D5s PSF), the FOC is extremely sensitive to
focus changes. Between the final focus and alignment carried out for SMOV (essentially
achieved by the beginning of 1994) and the next focus adjustment six months later, the
focus for the FOC appeared to change by approximately 6 microns. This amount of
defocus resulted in a considerable degradation of the PSF quality. For example, the
pseudo-Strehl ratio (the fraction of the total flux that landed in the peak pixel) decreased
=66rom its post-alignment optimum of 9% to 3% prior to the focus adjustment for the F210M
filter. This defocus, caused by OTA desorption, was corrected for by a 5 micron change in
the OTA secondary position and a 1 micron secondary-equivalent change in the Deployable
Optical Bench (DOB) position of COSTAR (carried out on 29 June 1994 and 9 August
1994, respectively). Subsequently, there has been the need for another 3 micron
secondary-equivalent adjustment using the DOB (23 October 1994). We have instituted a
regular observing program to monitor focus which runs every 5 to 7 weeks. This should
ensure that the FOC focus remains near optimum. The observer should keep in mind,
however, that there can be as much as 5 micron peak to peak variations in effective focus
due to an orbital =D2breathing=D3 effect which currently cannot be co
rrected.

Photometry
There has been a change to the Detector Quantum Efficiency (DQE) curve used by
SYNPHOT and the calibration pipeline which follows a change in the definition of the DQE
curve itself. First, it is based on the new UV standard spectra which now use as a primary
calibrator G191B2B (see accompanying article by Bohlin and Colina). Second, it reflects
the new definition of the aperture used to normalize the flux from a point source. This and
subsequent DQE curves will use the flux measured in 1 arcsec radius aperture as a basis to
derive the total flux. Prior DQE curves were based on a 3 arcsec radius aperture. A direct
comparison of this curve with the previous ones will result in an apparent lowering of the
present DQE in the UV, where there is a non-negligible fraction of the flux falling outside
of the 1 arcsec radius aperture but within a 3 arcsec radius. The straight line fit to the data
points shown in Figure 1 represents the ratio of the new DQE curve using the new standard
star spectra and aperture to the old DQE curve. This change to the DQE curve was installed
in the calibration pipeline on 3 November 1994.
It was discovered that images taken with the FOC/COSTAR between 1 January 1994 and
19 April 1994 suffered from a problem with the calculation of the photometry keywords.
During this period, the standard pipeline calibration of FOC/COSTAR images did not
recognize the addition of the COSTAR reflectivity when calculating the PHOTFLAM
keyword. This resulted in errors of 20% or more in the values of the keyword. The proper
value can be calculated using the SYNPHOT package under STSDAS. All the observers
who obtained FOC data in this timeframe have been notified.
Preliminary analysis of exposures intended to check the correctness of the transmission
curves for the ND filters indicate some discrepancies. Although the F1ND filter appears
consistent with its transmission curve, it appears that the F2ND and the F4ND filters may
have as much as 10% and 20% less throughput than their transmission curves predict.
Since the data are still somewhat incomplete we cannot change the transmission curves
without more information. Those observers who require good absolute calibration and use
those filters (as well as the F6ND and F8ND filters) should contact the FOC group at
STScI for further information.

Pointing
We have been monitoring the alignment of the FOC apertures with respect to the spacecraft
and find that our pointing is accurate to within 0.1 arcsec. Also the fiducial reference point
of the FOC aperture has been moved from the image center to a nearby point at (556, 536)
for the full format. The same shift from the old center applies to all the other image formats
as well. The reason for the change of reference point is that there was a reseau close to the
image center, and this change minimizes the possibility that the target will be imaged on or
near the reseau.

=D1 Antonella Nota and Perry Greenfield,
FOC Instrument Scientists

FOS INSTRUMENT NEWS
The observationally-derived post-COSTAR absolute photometric calibration (IVS) was
installed for routine use in the post-observation pipeline on 21 March 1994. Subsequent
Cycle 4 standard star observations have indicated calibration uncertainties of 3-10% with
the largest differences for the smallest apertures and shortest wavelengths. No additional
updates to the calibration are planned until further Cycle 4 standard star observations have
been made in order to establish a longer temporal baseline.
The absolute reference system for FOS flux calibration has been changed commencing with
post-COSTAR observations. As of 1 February 1994 all FOS observations are placed on the
reference system defined by a pure hydrogen white dwarf model atmosphere for the
spectrophotometric standard G191B2B. Most fluxes in the region 1300-3000 =81 will be
increased between 5 and 10 percent when compared to the previous flux scale. A detailed
description of the new calibration accompanies this article.
Post-COSTAR flat field calibration of the high dispersion gratings was installed in the
pipeline reduction system on 13 July 1994. This calibration is based upon 4.3 aperture
observations. Initial analysis of flat field observations for other apertures indicates that the
aperture-dependence seen in pre-COSTAR flat field structure is either not present or is
dramatically reduced in post-COSTAR spectra. All high-dispersion observations obtained
prior to 13 July 1994 should be re-calibrated with the new flats. Fla
t fields for low-
dispersion spectra will be available shortly.
FOS Instrument Science Report CAL/FOS-130 provides a complete listing of all the
recommended Cycle 4 calibration reference files and tables. This document gives a
complete discussion of the Cycle 4 calibration status of the FOS as o
f November 1994.
Many FOS ISRs are now available online on the new FOS WWW Homepage (see
accompanying article by Warren Hack). Additionally, the separate text-oriented anonymous
ftp directory for the FOS (on the Space Telescope Electronic Information System, STEIS)
has been completely re-organized into new sub-directories by topic and new explanatory
text files have been added.
FOS plate-scale, aperture sizes, and precise aperture locations were all determined in
SMOV - see CAL/FOS-121 and CAL/FOS-123. Observations with all apertures are now
routinely being scheduled.
A new scattered light correction algorithm was added to the post-observation pipeline in
mid-April 1994. For certain detector/disperser combinations, including FOS/BLUE
G130H, a wavelength-independent correction is made for grating-scatter plus residual
detector background. The latest version of the STSDAS FOS calibration software,
CALFOS version 2.0, includes this new algorithm. See CAL/FOS-103 for background on
the new methodology.
A new flux calibration algorithm for PRE-COSTAR non-polarimetric observations has
been devised (see CAL/FOS-125 and -129). The new method in STSDAS CALFOS
incorporates known changes in FOS instrumental photometric sensitivity as a function of
the date of observation, secondary mirror position, and aperture for all detector/disperser
combinations. The new method produces substantially improved fluxes f
or all PRE-
COSTAR observations and is the method of choice for any pre-COSTAR archive research
analyses. The updated procedure produces fluxes on the new white dwarf model
atmosphere absolute system as well. Please contact an Instrument Scientist or refer to
CAL/FOS-129 for details pertaining to the implementation of the new m
ethod.
Some post-COSTAR FOS polarimetry capability has been verified. The G190H and
G270H spectral elements may be used. Polarimetry with the G130H grating is no longer
feasible. Please contact an Instrument Scientist for details. Cycle 4 monitoring of FOS
location of spectra (y-bases) has shown systematic drift for FOS/BLUE. FOS/RED y-base
drift can not be verified currently. Y-bases are being updated period
ically as required.

=D1 Charles D. (Tony) Keyes
FOS Instrument Scientist

GHRS INSTRUMENT NEWS
The characterization of the GHRS following SMOV is essentially fully complete. New
sensitivity calibrations have been made for all the gratings except G140M, which will be
done in December. New vignetting files are also available for nearly all grating-aperture
combinations. Vignetting observations for G140M will be made in December while
vignetting for Echelle-B + SSA and G200M + LSA are being determined and will be
available very soon. The scattered light coefficients have been redetermined for Echelle-B
and are in progress for Echelle-A.
These files and their use are described in GHRS Instrument Science Report 67,
=D2Calibration Product Review for the GHRS in Early Cycle 4,=D3 available over STEIS. We
recommend that observers read ISR 67 to find out which are the latest calibration files and
the data to which they pertain. For example, the recently-determined SSA vignetting files
can be used on all pre-SMOV data as well as on recent observations.
There were previously vignetting files only for the LSA so that SSA observations were
reduced with the LSA files. Calibrations now exist for both apertures, and STSDAS CAL
HRS has been modified to take account of aperture in applying the vig
netting correction.

GHRS Stability Since SMOV
The sensitivity of the GHRS appears to be stable, as judged from regular executions of the
sensitivity monitoring program. There is marginal evidence for a slight (few percent)
decrease in sensitivity below 1200 =81, but that could arise from a number of effects
unrelated to actual instrumental sensitivity as such. This, of course, is being studied
further.

FOS-Assisted Acquisitions for the GHRS: A New Acquisition Mode
Version 5 of the GHRS Instrument Handbook mentioned a new acquisition mode that we
expected to have available in Cycle 5. In this mode an object too faint to acquire with Side 1
of the GHRS (because of the 12.75 maximum STEP-TIME) can be acquired with the FOS,
followed by a blind offset to the GHRS LSA and an ACCUM with G140L (for example).
A test was run of FOS-assisted acquisitions for the GHRS and it was successful. We
expect to support such activities in Cycle 5.

The GHRS in Cycle 5
The Cycle 5 TAC was advised that all GHRS capabilities should be available to GOs in
Cycle 5, including full use of Side 1 (G140L, G140M, and Echelle-A).

Communications
A GHRS home page may be found within STEIS, and from it one may access our
Instrument Science Reports, the Instrument Handbook, etc. Please let us know how this
may be improved. If you use Ghostview to examine the PostScript documents, they may
be unreadable unless you zoom in to a Magstep value of 2. We are working to provide true
html documents.

Doppler Compensation for Moving Targets
Just before the SL9/Jupiter campaign, it was found that the Doppler corrections made for
moving targets were done incorrectly because account was not taken of the true positions of
the targets at the time of observation. That has been remedied for observations made in July
1994, and thereafter. Moreover, we have found that it is possible to compute what the
Doppler correction should have been for a given observation and what was actually done,
and thereby apply an after-the-fact correction so that spectra are properly aligned. We have
advised PIs of moving target programs of this, but if you need more information please
contact a GHRS Instrument Scientist.

=09=09=D1 David Soderblom
Lead Instrument Scientist, GHRS

WFPC-1 INSTRUMENT NEWS - COMPLETION OF CALIBRATION =09PROGRAM
The WFPC-1 group (Sylvia Baggett, John Biretta, John MacKenty, Christine Ritchie, and
Bill Sparks) announces completion of the WFPC-1 calibration. Highligh
ts include low-
noise bias and preflash reference files, completion of time-dependent dark calibration
through the end of the WFPC-1 mission, a new series of Cycle 3 Earth flats and delta flats,
and a new product called =D2high fidelity flats.=D3 These and other calibration products are
described below and listed in the latest =D2WFPC Reference Files=D3 memo, which is available
on the Space Telescope Electronic Information Service (STEIS, available now on World
Wide Web).
Low-noise bias and preflash reference files were generated for both the WF and PC camera
using large numbers of on-orbit frames. These will give reduced noise for science
observations where many (>10) frames of the same field are averaged together. We note
that the Medium Deep Survey (MDS) team (R. Griffiths, PI) has provided a WF camera
preflash reference file with an improved CTE correction, which will significantly improve
calibration of non-preflashed images of faint targets.
The time-dependent dark calibration has been completed through the end of the WFPC-1
mission. At total of 22 dark calibration reference files track the dark current evolution
between July 1991 and December 1993. The MDS team has generated reduced-noise
variants for some of these files, and they are included in the archiv
e.
Approximately 1400 exposures of the bright sunlit Earth (Earth flats) were obtained in
Cycle 3 (July to December 1993), and these have been analyzed and combined to produce
84 new flat field reference files. This new set supplements previous flats which were
observed during the WFPC-1 SV and Cycle 1 eras (mid-1991 to early 1992). The new flats
have the advantage of calibrating Cycle 3 data without separate =D2delta flat=D3 corrections for
detector QE changes and the formation of =D2measle=D3 contaminants. In addition, the Cycle 3
flats include many filters in combination with the F122M and F8ND neutral density filters,
thus offering important new tools for removal of flat field artifacts. We have also generated
a new series of delta flats which adjust these Cycle 3 flats for application to data taken in
Cycle 2. These Cycle 2-3 delta flats cover 15 filters in the WF camer
a, and 12 in the PC.
=D2High-Fidelity Flats=D3 are a new calibration product wherein the g
oal is to provide flat-
fielding accurate to +- 2% over most of the field-of-view. These are typically computed
=66rom ratios of the standard Earth flats where various artifacts are made to cancel. The
corrected artifacts include a 25% gradient imposed on the WF broad-band flats by the
F122M filter, and the 5-10% short exposure reciprocity error seen in 
most of the narrow-
band flats. Most filter / camera combinations have two =D2hi-fi=D3 flats-one optimized for very
short exposures (<1 sec.) and one optimized for long exposures (>>1 sec.). We have also
generated separate series of hi-fi flats which are applicable to Cycle 2 and Cycle 3 data
(i.e., where the deltaflat correction is incorporated in the Cycle 2 version). The STEIS
memo =D2WFPC1 Flat Field Closure Calibration=D3 describes this new pr
oduct in more detail.
Photometric monitoring and tracking of contamination-dependent throughput variations
was completed through Dec. 1993, and the results are tabulated in the STEIS memo
=D2WFPC1 Photometric Monitoring Results.=D3 The capability of performing time-dependent
photometric calibration using these corrections has been added to SYNPHOT. Standard
star observations were made in nearly all the WFPC-1 filters during Cycle 3. These data,
together with the hi-fi flats, have been used to update the WFPC-1 SYNPHOT DQE
curves. A report describing the final photometric calibration is in preparation (Sparks et
al.).
The completed WFPC-1 PSF library contains 1187 PSFs observed between May 1991 and
November 1993. Most of the 905 observed in the PC are on detector PC6 and cover 14 of
the most-used filter; there is a small number on the other PC CCDs. For the WF camera
there are 282 PSFs covering 8 filters. A listing of these PSFs with their detector locations
can be found in =D2WFPC Observed PSF Library=D3 by Baggett and MacKenty in the
Proceedings of the HST Calibration Workshop. These, and all the above calibration
reference files, can be listed and retrieved using the STARVIEW HST a
rchive interface.

=D1 John Biretta,
WFPC-1 Instrument Scientist

WFPC-2 INSTRUMENT NEWS
In addition to the instrument handbook (STScI publication Version 2.0, edited by Chris
Burrows) that was updated since the refurbishment mission, there is a general description
of the instrument status and performance by Trauger et al. (Ap.J. Lett., v.435, L3) 435 3,
and a more detailed calibration discussion in Holtzman, et al. (PASP, in press). There is
also an instrument science report (ISR) available from STScI that discusses the pipeline
calibration and present state of the reference files that make up that calibration, and another
ISR that covers the scattered light performance in the WFPC-2 cameras. In addition the
software packages TIM and TINY TIM that model the WFPC-2 PSF have been extensively
updated to reflect the detailed knowledge of the aberrations present in WFPC-2 that has
been obtained from on-orbit data (Krist and Burrows, Applied Optics, in press). All of
these references can be obtained on request from the User Support Branch. Observers are
also encouraged to consult the instrument home page available through the World Wide
Web (see the article by Warren Hack in this issue). Instrument calibration and performance
issues of interest to observers are documented in these references in some detail.
Significant changes in our knowledge since the Handbook was prepared are in the areas of
photometric calibration, charge transfer efficiency, dark pixels, instrument contamination,
and scattered light. These issues are described briefly below, with pointers to the more
detailed discussions elsewhere.
The photometric calibration of the instrument is still being refined. The calibration in the
Handbook is the same as that provided to observers through the pipeline, and the same as
that obtained by running SYNPHOT under IRAF or XCAL. It is accurate to 5-10% in
almost all filters. Preliminary corrections to the handbook values can be obtained from the
PASP calibration paper.
Charge transfer efficiency (CTE) is a CCD defect that afflicts WFPC-2. It produces a
variable effect on photometry depending on the scene. In the worst case (bright stars on a
low background), the effect is to introduce a decrease in the number of photoelectrons that
actually reach the amplifier by about 4% over the height of the chip (with consequent
changes in photometry). For sources with only a few hundred photoelectrons to start with,
the effect is much less and may be close to zero for stars on a high background (like distant
cepheids).
Since launch, rates of particle damage to these CCD devices have been higher than
expected. This damage manifests itself by causing the dark rate of individual pixels to
increase. This damage is =D2annealed=D3 during monthly decontamination cycles when the
CCDs are warmed up. Then some of the affected =D2hot=D3 pixels return to normal dark rates.
Detailed statistics on hot pixels are available, but the main point for observers is that they
should consider recalibrating their data with darks taken in the same week. Such
recalibration may be necessary for cosmetic reasons or in order to avoid photometric errors
or false detections of faint sources. The calibration applied in the pipeline is usually 4
weeks out of date.
Observers should be aware that there are significant changes in far UV throughput (of
about 30% in amplitude for F160W and F170W). Some changes are also measurable in the
F336 bandpass, but then only at the level of a few percent. Photometry longward of this
filter is believed to be unaffected at the 1% level. The throughput follows a sawtooth
pattern with a monthly period. Each month the instrument is decontaminated, and this
always seems to fully restore the throughput to its best level. Then the throughput
decreases monotonically during the month.

=D1 Chris Burrows
WFPC-2 Lead Instrument Scientist

Astrometry with WFPC-2: Geometric Distortion Correction
WFPC-2 can be used to make astrometric measurements. A major use of this capability is
to aid in WFPC assisted Target Acquisition. A WFPC-2 image taken before primary
science observation can be used to refine ground-based coordinates of objects to be
acquired by the small-aperture instruments, the FOS and GHRS spectrographs. Each of
these functions requires spatial measurements to be correct to much less than the 0.1 arc
second size of the WFPC-2 pixels. (While the PC has a higher resolution, it also has a field
of view which is insufficient for most offset pointing operations.) However, there are
geometric distortions in the optical system of each camera in WFPC-2 which cause the
observed positions of stars to shift from their actual positions by a few tenths of a pixel
near the center of the chip, and up to about three pixels at the edges of the chips.
This article describes the techniques we used to map the two-dimensional distortion
function of each camera. Once the functions were determined, it was a simple matter to
invert them, creating an algorithm to restore measured stellar positions to their actual
relative positions.
As in the case of WFPC-1, it should be stressed that the astrometry derived from WFPC-2
images has a very high relative accuracy (4-10 mas). In an absolute sense, however, the
coordinates derived from it are only as good as the knowledge of the position of the guide
stars used for the observation, and of the location of the WFPC-2 in the focal plane (0.5 - 1
arcsec). Usually this is not a problem, since the main use of WFPC-2 astrometry for other
instruments is to determine an accurate offset between the target to be observed with, say,
FOS, and a nearby easier to acquire object. The instrument onboard target acquisition will
then zero out any inaccuracies in the absolute position by picking up on the nearby object.
Although shifts of the camera positions with respect to each other ar
e less likely in WFPC-
2 than they were in WFPC-1 (no pyramid movements), best results will be achieved if both
target and offset star are on the same chip. The solution presented here, and implemented in
the =D2metric=D3 task in STSDAS, assumes observations through filters centered around the V
bandpass.
In order to determine the correction, images of NGC1850 were obtained in the F569W
filter at 5 overlapping pointings. Each of the 4 outer pointings were offset from the central
pointing by 20 arcseconds in both x and y. A separate set of exposures were taken to fit the
PC chip, and the outer pointings were offset 8.5 arcseconds in both dimensions. The
images were CR-split 7:3 to aid in removing cosmic rays. The images were processed
using the standard pipeline calibration system used at STScI.
The IRAF package DAOPHOT was used for the analysis of the data. The DAOFIND utility
was used to find all of the stars in the central pointing. The initial coordinate list was then
edited by examining the image at each of the coordinate values and eliminating spurious
entries such as diffraction spikes, cosmic rays, or noise in the background. This edited
coordinate list was then used to create the coordinate lists for each of the overlapping offset
pointings by applying the appropriate offset values to the coordinate values in the initial list.
These coordinate lists were run through the PHOT program with the centered centering
algorithm turned on, in order to get accurately centered coordinates and an estimate of the
magnitudes. The photometry files were further processed to eliminate stars with poor or no
magnitude estimates, which indicated that the star was too faint to get an accurate
magnitude and therefore was not accurately centered, or that the coordinates were outside
the region that overlapped with the offset pointing.
The observed positions of the each star which appeared in overlapping central and offset
exposures were tabulated. The stars were expected to move by a certain distance in X and
Y due to the telescope maneuver from the central pointing to the pointing of the overlapping
offset image and the difference between the expected and observed positions were
computed and used as the basis of the distortion mapping.
To determine the correction to the geometric distortion, an iterative process similar to the
one developed by Gilmozzi and Ewald for WFPC-1 was used. The offset and residuals of
each quadrant with respect to the central pointings were fit using 3rd order Legendre
polynomials. The derived solution was applied to the central pointing only, then residuals
and offsets were re-calculated and fit again. The solutions derived from each iteration were
applied to a set of independent control fields comprised of stars from the overlapping
regions of adjacent offset pointings. The iterative process was terminated when both the
rms of the fit and of the control fields reached a similar value, typically 0.07-0.10 pixels.
This was necessary to check that systematic effects introduced in the data by the maneuver
calculation in each iteration were properly removed. The result is shown in Figure 2.

=D1 Roberto Gilmozzi, Ellyne Kinney (STScI), and Shawn Ewald (JPL)

ABSOLUTE CALIBRATION OF HST
HST White Dwarf Based Calibration
In the past, optical (3200 - 8500 =81) HST calibration has been based on a set of Oke=D5s faint
spectrophotometric standards. In the UV wavelength region (1150 - 3200 =81), the HST
spectrophotometry was traceable to the IUE spectrophotometric system.
Starting with Cycle 4, the absolute flux calibration of the HST spectrographs and cameras
over the entire 1150 - 8500 =81 wavelength range is on a preliminary WD scale (Bohlin
1993, STScI ISR on Standard Calibration Sources, CAL/SCS-002). A pure hydrogen
model of the white dwarf G 191B2B with an effective temperature of 60,000 K and gravity
of log g==7.5 (Finley, private communication) is the flux reference standard. The zero point
of the new WD-based absolute scale is obtained by calculating the synthetic V magnitude of
the G 191B2B model spectrum in Landolt=D5s photometric system and adjusting the model
flux to Landolt=D5s observed magnitude,                V== 11.776 +/- 0.002. The resulting FOS
fluxes for 4 stars in the optical agree with Landolt photometry to 1% (Colina & Bohlin
1994, AJ, v.108, p.1931). The calibration procedure for the Faint Object Spectrograph
(FOS) in the WD-based system is explained in detail in the FOS Instrument Report
CAL/FOS-125 (Lindler & Bohlin 1994).
The FOS spectrum for G 191B2B is divided by the model spectrum to derive the difference
between the old HST flux scale and the flux scale in the new WD-based system. Changes
in the ratio of NEW/OLD optical fluxes are less than +3%. Samples changes in the ratio of
NEW/OLD UV fluxes are:

Wavelength (=81)=09Change (%)
1200=09-5
1400=09+13
1500=09+5
1600=09+12
1800=09+8

Wavelength (=81)=09change (%)
2000=09+7
2200=09+7
2400=09+4
2600=09+4
2800=09+5

Presently, FOS observations of three more white dwarfs (GD71, GD153, and HZ43) with
effective temperatures in the 30,000 - 50,000 K range are being carried out in order to
obtain the final WD-based calibration of HST. No changes by more than 5% with respect
to the preliminary G191B2B based calibration are expected.

=D1 Ralph Bohlin and Luis Colina
Calibration Scientists

HST VERSUS IUE ABSOLUTE CALIBRATION
As mentioned in the accompanying note, the absolute flux calibration of the spectrographs
and cameras on HST has been switched to a preliminary white dwarf (WD) scale. The flux
calibration of IUE for the Final Archive (NEWSIPS) is also different =66rom the one in the
current processing pipeline (IUESIPS). Although the principle of both HST and IUE
calibrations has similar aspects, there are substantial differences that lead to discrepancies in
the flux level of spectra of the same object.
The photometric calibration for the IUE Final Archive is based on WD models and OAO-2
fluxes. The IUE/NEWSIPS inverse sensitivity function has been derived from a pure
hydrogen model of the WD G 191B2B with an effective temperature of 58,000 K and a
gravity of log g == 7.5 (Finley, private communication). The zero point of the new flux
scale is defined by the OAO-2 fluxes of the brightest IUE standard st
ars in the range 2100-
2300 =81. (Gonzalez-Riestra et al. 1993 in Proc. Conf. Calibrating Hubble Space
Telescope). The 2000 K difference in the temperature of the WD G 191B2B models
produce a maximum difference of 1.3% in flux (Colina 1994, STScI ISR on Standard
Calibration Sources, CAL/SCS-003).
Considering the different choices in the G191B2B models and in the zero point of the
absolute scales, a difference by a factor of 1.054 between the HST/FOS and
IUE/NEWSIPS fluxes is expected (Colina 1994, CAL/SCS-003). The HST/FOS spectra
are brighter. This value agrees with the average value of 1.061 for the ratio of the FOS to
the IUE/NEWSIPS spectra of the primary standard G191B2B over the IUE 
spectral range.
In summary, the new HST/FOS calibration on the WD scale produces fluxes that are 6%
larger than IUE/NEWSIPS fluxes, independent of the wavelength over the entire IUE
spectral range. Any potential user of HST post-COSTAR and IUE/NEWSIPS data should
be aware of this discrepancy.

=D1 L. Colina (STScI), R. Bohlin (STScI), R.Gonzalez-Riestra(VILSPA-I
UE),
W. Wamsteker (VILSPA-IUE)


NEWS FOR HST OBSERVERS AND PROPOSERS
 ST USERS COMMITTEE REPORT
The Space Telescope Users Committee (STUC) met on 8-9 September 1994 at STScI. The
STUC met jointly with the Servicing Science Working Group (SSWG) on the first day to
review the project status, budget, and prospects for long-term operation of the spacecraft.
The second day was concerned largely with interaction of HST users wi
th the STScI.
With regard to material presented jointly to the STUC and SSWG, we summarize as
follows:
1. The HST project manager presented a somber status report on flight spares for the 1997
refurbishment mission, as well as the long-term plans for developing advanced spare
components (fine guidance sensors, batteries, solid-state data recorders, gyros, and so on)
that would be required to ensure operation of HST over its full 15-year mission. The recent
budget cuts applied to the project have essentially curtailed all work on second-generation
flight spares, leaving the project with a small inventory of parts on hand to service any
component failures that may occur prior to the 1997 mission. The project also reported that
additional 10% budget reductions have been requested from 1996 on. The project could not
identify additional savings to be obtained without resorting to a number of options that the
STUC considers to be extremely unattractive. These include waiving the HST Level I
requirements, terminating the Advanced Camera, reducing the data analysis money by
greater than 50%, and so on.
We find that at the very minimum, the HST project is not being allowed to plan sensibly for
long-term support of the 15-year mission due to the projected shortage of money required
to develop and support the hardware required. We are further concerned that if component
failures on orbit continue as they have in the past, operation of the spacecraft more than a
few years into the future may be at serious risk. We further find this situation remarkable,
given 1) the investment made to the program so far, 2) the success of the repair mission, 3)
the demonstrated performance of the repaired telescope, all leading to 4) the keen interest of
the public in the recent discoveries made by the repaired telescope.
The STUC has the distinct impression that the perception still exists, both within NASA
and without, that the HST budget can be further reduced without seriously jeopardizing the
future scientific returns from HST. We are surprised by the persistence of this perception,
given that none of the six reviews of the project budget conducted so far this year (one by
the STUC itself) have been able to identify excess monies or savings to be obtained that did
not have an adverse effect on the operation of HST.
2. The STUC was briefed on the current plans to expand the role of the STScI in NASA=D5s
educational and public outreach activities and views the STScI role as an important way to
disseminate to Congress, NASA, and the general public the remarkable scientific results
now being obtained in spite of a dangerously tight budget. The STUC is willing to
contribute to this effort in any way that it can.
3. The STUC commends the Project on restoring the Advanced Camera to the program and
issuing an AO to which all qualified proposers may respond. However, we are concerned
that at the level of funding envisaged, the resulting instrument may not be a significant
advance over WFPC-2; in this case we feel that the question of proceeding with funding for
the AC as opposed to other pressing HST needs should be carefully examined. We
strongly support efforts to enlist funding support from other individual nations or groups to
enhance the performance of the AC. We note that the =D2Frontiers of Space Imaging Study=D3
clearly identified the Advanced Camera as a means to enhance and ensure continued
scientific returns over the lifetime of the HST mission, a point of v
iew that we endorse.
4. STIS and NICMOS remain on schedule and budget for the 1997 mission. The project
clearly understands that withholding money from either instrument at this late stage will
ultimately only result in delayed deployment of the instruments and larger long-term costs.
We understand that with modest effort, it may be possible to equip STIS with additional
optical and UV filters. This may be an attractive =D2insurance=D3 option for providing some
UV, or even optical imaging capability, should FOC or WFPC-2 fail prior to deployment
of the Advanced Camera. We encourage the project and STIS team to investigate this
option.
With regard to material presented solely to the STUC, we summarize as
 follows:
1. The STUC was very impressed by both the execution and the high quality of the
scientific data that came out of the HST observing campaign during the impact of the
fragments of comet Shoemaker-Levy 9 with Jupiter in July 1994. We commend the STScI
and all of the individuals involved. Of particular note was the organization beginning with
the call for proposals, through the mini-TAC review and selection, and the subsequent
prompt funding of investigators which ensured adequate planning and preparation. This
latter contributed not only to the high quality of the results but also to their prompt
dissemination to both the public and the astronomical community. This experience should
provide a model for future HST observing campaigns.
2. The STUC notes a minor breakdown in communications regarding the c
ompletion of on-
orbit characterization and calibration of the scientific instruments following the successful
repair mission. In one particular example, GHRS side 1 data obtained through mid-summer
1994 were processed in the pipeline using pre-repair mission theoretical sensitivity curves,
yet users of this instrument were not directly notified when the on-orbit calibration files
became available. This information was duly placed in STEIS (dated 20 July 1994), but it
is clear that the members of STUC (and probably most users) do not browse in STEIS
unless notified of the need to do so, preferably by e-mail. In general, we ask that STScI
alert observers upon receipt of their observations of any outstanding
 calibration problems.
3. We reviewed the plans for evaluating Cycle 5 proposals, and note that the number of
panels has expanded from 6 to 8. We note that the division of proposals into various
categories, while necessary, is somewhat arbitrary and should not in any case be used as
criteria for dividing telescope time among the various sub-fields of interest. STScI has
expressed its goal of encouraging the TAC to allocate time in an attempt to define the best
science program overall, regardless of the mix of problems, and we encourage this
approach. We also commend STScI for changing the allocation from spacecraft time to
orbits for Cycle 5, as well as for implementing greatly simplified pr
oposal forms.
4. We commend STScI for development of the PRESTO and POSS programs to assist
observers with development of their Phase II proposals and reduction of observations once
their observations have been obtained. We find it attractive to be able to interact with a
small group of individuals for the wide variety of problems that may arise in the planning
and reduction of observations. We especially endorse having a responsible Ph.D. level
person (with associated support staff) as being THE contact for any given program. At the
same time, we strongly support the creation of a single database structure where the status
of any proposal or problem is tracked by the system itself, rather than the memory or
availability of any single person. It is extremely important to ensure that programs do not
=D2fall through the cracks=D3 at any stage of their implementation. Portions of this database
should be available to the outside users, with due regard to the security of the individual
GO proposal.
A key aspect of the POSS approach is the analysis =D2hotseat,=D3 which provides a constantly
available and monitored point of contact to STScI. We recommend adoption of a hotseat
phone or e-mail contact by the PRESTO program, and all other STScI programs involving
extensive contact or interaction with HST users. We also urge that all such hotseat or
general points of contact be clearly posted as an ongoing feature in each STScI Newsletter
issue.
5. The STUC is also concerned with having the best scientific advice available for
preparation and analysis of the observations. In short, understanding what an observer is
attempting to accomplish and forestalling problems will in many cases require interaction
with STScI staff capable of understanding both the technical and scientific aims of the
proposals. We thus encourage involvement of the STScI research staff in both the
PRESTO and POSS programs.
6. We suggest that STScI clarify the definition and utility of dark-time (that is the portion of
the orbit during which the spacecraft is within the earth=D5s shadow) for programs that
require the lowest backgrounds. This has become especially important now that users must
fill entire orbits. We wish to know under what imaging and spectrosco
py conditions dark-
time should be requested, and suggest clear instructions be added to the Phase II
handbooks. Similarly, we recommend that STScI work with T. Ake from GSFC to
implement a low particle background scheduling algorithm for those programs for which
this is an important requirement, along with the relevant documentati
on and instructions.
7. We were pleased to see that the STSDAS group continues to upgrade this software
package in a time of decreasing man-power, and were pleased to see their cautious
approach in converting (parts of) STSDAS to a C or C++ environment, avoiding the many
pitfalls that other observatories have encountered in similar transitions. We urge that the
STSDAS group be able to continue their important work, as many HST users depend on
this software package as their sole environment to reduce and analyze
 HST data.

=D1 Tod Lauer (STUC Chair, NOAO)
for the ST Users Committee

STEIS AND WWW NEWS
STEIS Reorganization
The amount of information available through the WWW pages at STScI has grown rapidly
in the last year. At last count there were approximately 300 hypertext markup language
(html) pages on STEIS. It became apparent that our Web had outgrown its initially very
informal structure. Thus, we set out to improve the overall organization of our Web, as
well as the look and feel of the top level pages. A html design committee was formed
consisting of Zolt Levay, Mark Stevens, and Chris O=D5Dea to carry out this goal. The new
home page (shown in Fig. 1) is very simplified and streamlined. The Web has been divided
into seven major topical areas, each acessible via a button =D1 STScI, Public, Proposer,
Instruments, Observer, Software, and Archive. The STScI page includes, e.g., the Library
and Institute publications, the Guide Star Catalog and Sky Surveys, meetings and
workshops, the PASP, and visitor information. The Public page includes materials for
Educators and Students, HST-based pictures and animations, Press Releases, and
Exploration in Education. The Proposer Page contains documents, templates, and software
relevant to HST proposers. The Observer page contains HST status reports, the telescope
schedule, program status, and data reduction help. The Instrument page includes
information on the performance and calibration of the instruments. The Instrument pages
have been greatly expanded and are described separately below. The software page
includes STSDAS, Tim and Tinytim, compression software, and Sky Survey CD-ROM
software. The Archive page includes catalogs of exposures and abstracts, and information
on browsing the archive and retrieving data. The URL address for STEIS is
http://www.stsci.edu/top.html. We welcome your comments on our new look. Please send
e-mail to usb@stsci.edu.

=D1 Chris O=D5Dea, Zolt Levay,
and Mark Stevens (STScI)

New Instrument News Mosaic Pages Available
A great deal of effort has been put into documenting the status of each science instrument
aboard the HST, but this information has not always been readily accessible. Electronic
media, such as the World Wide Web through the Mosaic interface, provide simple
mechanisms for making large amounts of information available in a comprehensive and
organized manner. The STScI has developed Mosaic pages for a wide range of
information. Now, each instrument team has taken advantage of this opportunity by
creating a set of pages filled with information never before available in electronic form.
These new pages can be accessed from the Instruments page on the STScI home page.
All the instrument science teams worked together to develop a common style for these
pages. This style creates an environment where observers can use their familiarity with one
instrument=D5s pages to find similar information from any of the other instrument pages. Each
instrument=D5s introductory page contains links to Advisories, Calibration Products and
Tools, Frequently Asked Questions, Manuals and Reports, the main STScI page, and a
directory of the instrument team members.
The Advisories section contains the latest news on the status of each instrument, including
changes in calibration information or perhaps even in the operation of the instrument. This
should be the first stop for any observer with HST data in order to see how any data they
have, or plan to acquire, might be affected. The date this section was last updated will also
be provided.
The Calibration Products and Tools section stands as one of the main repositories of
information regarding the calibration and status of the instrument. Descriptions of
calibration files and tables used during the standard =D4pipeline=D5 calibration of all HST data
can be found here. These descriptions provide a history of the calibration files for each
instrument and indicate which reference files are most suitable for any given HST data. In
addition, calibration information useful for post-pipeline reduction of HST data is also
listed here. The photometric monitoring information for the WFPC-2 and un-smoothed flat
fields for the FOC are examples of the types of additional calibration data that are available.
Many Frequently Asked Questions are addressed by topic in each instrument=D5s page. A list
of subjects can be searched on topics ranging from proposal preparation to data analysis.
These lists will be updated throughout the Cycle to quickly address some of the most
commonly asked questions regarding each instrument.
Manuals and reports produced by each instrument team were usually only available as
paper copies. However, each team=D5s Instrument Handbook and a set of Instrument Science
Reports (ISR) are now available in PostScript form. The ISRs document various
calibration efforts by each team and can be searched either through a complete list of ISR
titles or by topic keyword. At present, only the most recent reports are available in
PostScript form, but a convenient e-mail facility is provided to request paper copies from
the Institute. In addition to the Handbooks and ISRs, many other reports produced by each
team can be found in this section, resulting in an online documented 
history.
Finally, the teams have provided a directory of their members including areas of
specialization, e-mail address, and phone numbers. In addition to the
 directory, an online e-
mail form is provided for immediately contacting the team with questions. Observers now
have access to not only a great deal of instrument specific information useful for
understanding their data, but also to the people responsible for calibrating the instruments.
These pages represent an initial release with many sections containing only a preliminary
amount of information. They will, however, be constantly undergoing revisions with the
inclusion of more information as it becomes available. This knowledge, although quite
technical at times, can now be easily accessed in order to help observers get the best
possible science out of their HST data.

=D1 Warren Hack (STScI)

HST ARCHIVE NEWS
The New Archive System, DADS, is Now ON-LINE.
We are pleased to announce that the new HST Archive System, the Space Telescope
Archive and Distribution Service (or ST-DADS), is now in place. DADS was developed by
Loral and STScI for NASA. Over the course of the past year, we have been transferring all
the old data from DMF (the old archive system) into DADS, while directly archiving new
data from the telescope into both DMF and DADS in parallel. Finally, in September of this
year, when all of the science data was in DADS, we shut off ingest of new data into DMF
and switched all users from DMF to DADS, the permanent HST archive.
We have worked to make the change over from DMF to DADS largely transparent to users.
Users still access the HST archive in the same way as in the past- either telnet to
stdatu.stsci.edu (stdata.stsci.edu if you prefer VMS) or enter the HST archive through the
World Wide Web STScI home page (just click on archive information). Guest users can
enter the archive with username =D2guest=D3 and password =D2archive=D3. A guest has full access to
the HST catalog, but you will need to register (just type register from the command line) to
retrieve data.
Once on the archive host machines, access to the HST Archive is through StarView, the
interface to the HST archive. There is a crt version of StarView (type starview to start it up)
and an xwindows version of StarView (type xstarview). The crt version of starview has all
the features of the x-version, including an interface to SIMBAD and NED to determine
source coordinates and the ability to cross correlate lists of source coordinates with the
archive holdings. However, the x-version of StarView also allows preview of public HST
spectra and images. Since users may find xstarview slow to use if they are operating over a
slow network line, we also have a distributed version of XStarView available. To use this
you simply download the software from stdatu. It then takes roughly 5 minutes to install on
a Sun system and you are off and running. You can get more information about the
distributed version of XStarView via the World Wide Web archive pages or by typing
readnews on stdatu or stdata. Or, as always, you can just contact the archive hotseat
(archive@stsci.edu, 410-338-4547). They are available to help you get started using the
archive or to answer any questions about the archive or your HST data
 tapes.

Improvements to DADS
Though the transition to DADS has left most things the same, there are same important
changes. We hope that most of the changes will be seen as improvements! The new archive
system has all of the HST data online in its optical-disk jukeboxes, thus providing quicker
access to the data. Typical turnaround times for data retrieval from DADS are now roughly
one hour or less. Virtually all retrieve requests are satisfied within 12 hours (this can be
compared to the old DMF system in which typical turnaround times were ~5 hours, and it
could take from days to a week for large requests to be satisfied). Another advantage users
will see with the new system is that all the science data are stored and retrieved in FITS
format instead of the old STSDAS specific GEIS format. FITS is the astronomical data
format standard and has the advantage that it is operating system independent. Thus, you
no longer need to run byte-swap routines on data retrieved from DADS, as you did in the
past when retrieving data to UNIX systems.
There are also some changes in the StarView screens which you may notice. These reflect
the fact that the DADS database contains somewhat different information than DMF. In
addition, we have added a <PLANNED HST EXPOSURES> screen which you can use
either to search for information about planned observations of your favorite target, or to
find information about the status of your proposal. There are also new calibration screens
for the WFPC-2. StarView=D5s welcome screen now contains current news about the status
of StarView. Be sure to check it when you start up.
One final difference with the new archive system is that when you issue a retrieve request,
you won=D5t immediately get a request id number as was the case with DMF. Instead when
the Archive Machine receives your request, it will send an e-mail message back to you with
your request ID. (If DADS is busy this may take a little while.) ReqStatus in StarView will
be able to tell you about the progress of your request only after you have received this mail
message. After the archive engine completes your request and moves the data to stdata or
stdatu, then it will send you a second mail message, describing the files which were
retrieved successfully and those which were not. At that point, you may ftp the data back to
your computer. Each single retrieve request is limited to a maximum of 30 datasets at this
time, but you may issue multiple requests.
A new Archive Primer to accompany DADS is available in the documents directory on
stdatu and stdata or through World Wide Web. If you would like us to send you a paper
copy, please contact the archive hotseat (archive@stsci.edu).
Observation Log Files in the
HST Archive
Observation Log files for most science datasets taken after 20 October 1994 have been
produced in the pipeline and written to the HST archive. As described in detail in the next
article (by Lupie, Toth, and Baum), the Observation Log files contain a specialized set of
pointing and engineering data associated with each science exposure (including the jitter
information). You can retrieve them using StarView. Up to date information on how to
retrieve these files using StarView can be obtained by typing readnews on stdatu or stdata
or from the Archive World Wide Web home pages. By January, you will be able to retrieve
these files by first marking the science dataset in StarView (say on the <QUICK> or
<GENERAL> screens) and then selecting the Observation Log Files option on the archive
retrieval screen. In the nearer term, to retrieve the Observation Log files for a given science
dataset you will need to use the <Dataset Name> search screen. Enter the first 8 characters
of your science dataset followed by a J in the =D2Dataset Name=D3 field (e.g., for science
dataset F24P0201M enter F24P0201J) and begin the search. Once you have marked the
dataset for retrieval and passed through to the <Retrieval Default Specification> screen you
will need to choose the <Override Default Options> button and enter =D2OMS=D3 into the
archive class field. Then just press <submit request>. Remember, Observation Log Files
are only available for data taken after 20 October 1994.

COMING SOON - Changes in the HST Data Tapes for GOs
Beginning in February of 1995, GOs will notice some changes in their HST data tapes,
when we start up the DADS automatic tape writing software. When that happens, the first
file on the data tape will be the tape listing and will contain a description of the science
observations followed by a listing of all the files on the tape. The subsequent files will be
grouped by dataset name and will include both the standard pipeline raw and calibrated files
as well as the observation log files from the Observatory Monitoring System (see the next
article) and the data quality file. Following all the science data, the GO will find the
calibration reference files and tables used to calibrate their data by the Pipeline. Data will
take roughly 4-5 days to pass through the calibration Pipeline and can then be written to
tape. The GO data tapes are now being mailed out 2nd day UPS, so GOs should expect to
receive their HST data tapes within at most 14 days of their observat
ions.

=D1 Stefi Baum (STScI)
HERE COME THE OBSERVATION LOG FILES - OR HOW TO AVOID SPACE
TELESCOPE ENGINEERING XENOPHOBIA!
General Observers (GOs) will now have access to the =D2Observation Log Files=D3, as well as
their science data. The Observation Log files contain a specialized set of pointing and
engineering data associated with each science exposure (including the jitter information).
The calibration pipeline began routinely producing these files 20 October 1994, and the
majority of science datasets taken after that date now have Observation Log Files in the
Archive. These files are produced by the Observatory Monitoring System, an automated
software system which interrogates the HST engineering telemetry and 
correlates the time-
tagged engineering stream with the scheduled events as determined from the Mission
Schedule, the seven-day command and event list which drives all HST activities. The
Observatory Monitoring System reports the status of the instruments and observatory and
flags discrepancies between planned and executed actions. The Observation Log files have
the same first 8 characters as the rootname of the science exposure to which they pertain
and are composed of a header (with extension CMH) and several fits files. The FITS files
may be converted to STSDAS binary table format or images using the IRAF/STSDAS task
STRFITS. Tables maybe be manipulated using the STSDAS table tools (TTOOLS). The
Observation Log Files will not be written to the GO data tapes until February of 1995.
However, GOs whose data were taken after 20 October 1994 can retrieve the Observation
Log Files from the HST Archive using StarView (see the preceding arti
cle).
The Observation Log contains a plethora of interesting information, including material
needed in reconstructing and evaluating pointing stability and environment during a given
exposure. The Observation Log header file (CMH) contains, among other things,
keywords describing the requested and actual tracking mode achieved at the end of the
guide star acquisition process, the rms and maximum of the jitter (motion of the Fine
Guidance Sensors during the observation), the number of occurences of loss of lock and
recenterings, model estimates of Zodiacal light, stray Earth and Moon light, reconstructed
absolute pointing, and various angles (target to earth limb, target to ram direction and
others). The header also alerts the observer to slews occurring during an observation and
reports anomalies that can compromise the integrity of the science data (e.g., degraded
guide star acquisitions, losses of lock), or result in a failed observation (e.g., instrument or
vehicle safings, failed target acquisitions).
The tables contain pointing data and other parameters that are traced as a function of time
during an exposure. The engineering data are transmitted in a variety of formats, the
formats differing in their rates of update and information content. Because of the potential
for large amounts of data in the highest rate formats, we produce the CMI observation log
file, which contains 3 second averages of each parameter - providing a manageable data set
for quick look analysis. This table contains the vehicle coordinates of the guide stars during
an exposure and the vehicle and absolute coordinates (ra, dec, and roll) of the science
aperture (i.e., the jitter for fixed targets) as calculated from the guide star activity. It also
traces the day/night flag, recentering and loss of locks as a function of time, and telescope
slews. The CMI table also includes =D2environmental=D3 parameters such as the target-to-earth
limb angle, terminator angle, estimated stray earthlight, orbital information (latitude,
longitude, zenith angle, magnetic field), and a science-instrument specific column. Future
enhancements of the Log will include a time trace of telescope =D2breathing=D3 affects and
estimated model backgrounds given in instrument counts (these are now provided in V
mags      arsec-2). The jitter data at the highest possible time resolution is also available for
all observations. Initially observation log files at full time resolution - the CMJ extension
files - were produced for all science observations. However, as these files can get
excessively large and because the primary information of interest to an observer is the jitter
distribution, the pipeline ceased routinely producing full time resolution observation log
files in favour of producing a =D4jitter image=D5, containing a two dimensional histogram of the
jitter during the observation. This image loses the time tagging but preserves the full time
resolution jitter information. This jitter image can be used to derive a psf for image
deconvolution or to determine the light loss through the aperture due to jitter (in the case of
the spectrographs).
We emphasize to all users of these logs the importance of understanding the origin of the
parameters and their associated error bars before interpreting the results. For example, the
absolute pointing provided in the Log is reconstructed from the guide star data and the
guide star absolute coordinates, whose catalog errors are of order several tenths of
arcseconds. When the tracking mode uses the gyros only, the absolute pointing is
reconstructed from the gyro data which has time-dependent errors (due to gyro drift).
Documentation describing the details and accuracy of the Observation Logs is available on
line through the STScI home page of the World Wide Web - simply click on the documents
button. Hard copies of the OMS documentation, or help retrieving these files from the HST
archive, can be requested from the archive hotseat (archive@stsci.edu
).
Enjoy!

=D1 Olivia Lupie, Bruce Toth,
and Stefi Baum (STScI)
THE ANALYSIS TEAMS: A PILOT PROJECT TO IMPROVE POST-OBSERVATION
USER SUPPORT
A new initiative designed to improve the post-observation user support at STScI began on
October 1. The Analysis Team (== A-Team) is a pilot project developed to address your
main concerns, as determined from the post-observation user support survey circulated last
spring. The main goals of the project are:

 =A5=09Providing accurate, timely, and
=09easily understood calibration
=09information.

 =A5=09Optimizing contacts with STScI,
=09with the goal of providing a single =09=09point of contact for you
r post-
=09observation questions.

 =A5=09Improving documentation and =09=09analysis tools.

Each Analysis Team consists of an active research astronomer, one or two research
assistants, and a scientific programmer.
Since this is a pilot project, we are not able to support all Cycle 4 programs. Hence, only
WFPC-2 and FOS programs are being covered at present. In addition, very experienced
observers and observers with other means of support (e.g., Guaranteed Time Observers,
ESA observers, carryover proposals, most STScI staff, etc.) and programs that completed
before 1 October 1994 will not be covered in the initial plan.
In the future (i.e., Cycle 5) the analysis teams will merge with the instrument teams and
this approach will be expanded to include all four instruments. More details about the
program and the name of the person who will serve as the single point
 of contact for post-
observation support will be sent to Cycle 5 observers during Phase II
.
Although we are targeting a subset of proposals in Cycle 4, information of general utility is
being distributed to a wider audience via an electronic newsletter (STAN == Space Telescope
Analysis Newsletter), which comes out monthly. This newsletter has been developed in
concert with the Instrument Scientists and other staff at STScI to keep observers informed
about the latest calibration and analysis information. At present, separate newsletters exist
for the FOS, GHRS, and WFPC-2. These have been circulated to all Cycle 4 observers
who use these instruments. If you are not currently receiving this newsletter, but would
like to get on the mailing list, please contact analysis@stsci.edu.

=D1 Brad Whitmore
(STScI; A-Team Project Coordinator)

PRESTO Update: Plans for Cycle 5
PRESTO is the Project to Re-Engineer Space Telescope Observing, chartered in November
1993 to examine and improve user support during proposal development and
implementation, and during the planning and scheduling of the observatory (see the April
1994 STScI Newsletter). The project started by developing a new operations concept and
transition plan, then began to put the concept into practice. In the past year PRESTO has
made major changes in many areas. Among those most visible to date to HST proposers
and observers are:

=A5=09development of the Latex template
=09and submission process for Phase I

=A5=09the shift to time allocation by
=09orbits instead of spacecraft time

=A5=09a sustained high observing
=09throughput for HST =D1 about 50%
=09higher than in past Cycles

During this time, PRESTO has been developing a new framework for Cycle 5 which
embodies the best ideas for further improving the system. These improvements are
described in this newsletter in a series of articles covering:

=A5=09Program Coordinators and Liaison
=09Scientists =D1 the new contact team
=09for PIs for developing Phase II
=09observing programs

=A5=09RPS2 =D1 new proposal preparation
=09software tools for Cycle 5

=A5=09HST Planning and Scheduling =D1
=09what=D5s changed so far, what=D5s in
=09the works

=A5=09Observing program status via the
=09WWW =D1 easy to use, up-to-date
=09status of all HST observing
=09programs

=A5=09Failure reporting and follow-up =D1
=09the Hubble Observation Problem
=09Report

Demonstrations and posters covering these and other topics are planned for the January
AAS meeting in Tuscon. We especially encourage feedback and suggestions on how to
incorporate further improvements as we begin work on Cycle 5 observin
g programs.

=D1 Mark Johnston (STScI)

Program Coordinator & Liaison Scientist Teams
As part of the effort to improve the way we plan and schedule HST, PRESTO is making
significant changes to the way we support HST users. The pre-launch and early mission
concept of what it would take to process, implement and maintain Phase II observing
programs fell short of reality. As we gained experience, we added steps and people into the
process to meet the growing demands. Our experience has shown that increased numbers
of =D2hand-offs=D3 from group to group has its limitations, and can cause confusion about
whom to contact for information or when there is a problem.
Starting with Cycle 5, each approved HST program will be assigned a Program
Coordinator (PC) and a Liaison Scientist (LS). This team will serve as the point of contact
throughout the life of the observing program, from Phase II submission through execution.
Our goal is to provide high-quality support to observers on a person-to-person basis.
Where users once might have had more than one Technical Assistant assigned from
different STScI Branches, they will now have one Program Coordinator who will serve as
primary contact, even if they have more than one HST program. Attempts will be made to
maintain the same PC and Principal Investigator (PI) assignments across Cycles, but one
PC per PI is certainly the rule within the Cycle.
The PC/LS teams will take their assigned observing programs from initial Phase II
development and submission through the intermediate processing steps and on to the final
flight scheduling preparation. This will allow the experience gained during intermediate
processing and final flight preparation to more easily make its way back into the initial
development and submission stages so we can avoid the problems in the first place. While
TAs might have handled ~100 programs in past Cycles, the program load on the PC/LS
teams will be lower to enable them to focus more attention on the goals and requirements of
each program, to track the progress of the program, and to provide more individual service
and support HST users. This is an essential element of our plan to im
prove user service.
Another misconception we had was that once programs were submitted and flight ready,
there would be few changes required. Experience has taught us that observing programs do
change =D1 sometimes for very good reasons and other times due to lack of foresight and
simple human error. While we are making strides to simplify the Phase II process to help
observers spot and avoid errors, we are also working to create a more flexible process that
more readily accommodates change. The PC/LS team will remain in the loop with the
observer until all portions of each program have executed. To ensure that the user is fully
informed about the implementation of their HST program, a walk-through will be
conducted with the user that will include identifying the data to be obtained from each target
visit in the program, the planning window assigned to each visit, and when any subsequent
changes to each visit must be received in order to meet the planning window. While we are
not encouraging observers to wait until the last minute to make changes to their
observations, we do recognize that knowledge gained from one visit can be used to
improve the science obtained from subsequent ones.
While there is much technical work to be accomplished to develop and implement HST
observations, there are also numerous scientific decisions the user must make to specify
how to most effectively achieve their science goals with HST data. These questions often
span a wide range =D1 from specific instrument topics, to detailed planning questions, to
questions which require an understanding the capabilities of the HST vehicle and its
subsystems. Whatever the subject, it is the role of the Liaison Scientist member of the
PC/LS team to act as your colleague here at the STScI to help find the answers. The LSs
will also be working with the PCs and other members of the PRESTO Science Planning
and Scheduling Team (SPST) to ensure that actions taken or decisions made later in the
process maintain the integrity of the users=D5 HST observations. While the PC=D5s work is
essentially complete once all the data are taken for a program, the LSs will ensure the
transition of support to the Data Analysis Teams (A-Teams, described elsewhere in this
Newsletter issue) occurs smoothly and that subsequent user and A-Team questions or
issues related to program implementation or scheduling of the observation are properly
addressed.
PC and LS assignments have been communicated to successful Cycle 5 HST proposers in
their acceptance letters. We will convert the Phase I Latex submission into a Phase II RPS2
template (see the RPS2 article below) and then work with the proposer to help complete the
template.
Look for more information and software demonstrations at the January 
AAS in Tucson!

=D1 Peg Stanley, Melissa McGrath (STScI)

RPS2: New Phase II Proposal Preparation Tool
PRESTO has developed a new suite of proposal preparation tools for Cycle 5. The new
system is called RPS2 to distinguish it from the old Remote Proposal Submission System
(RPSS), although the new name correctly suggests that RPS2 is an evolutionary step based
on RPSS. The main advantages of RPS2 over RPSS are:

=A5=09a dramatically simplified proposal
=09template, allowing observers to
=09directly specify visits and their
=09associated exposures and
=09observing requirements

=A5=09graphical feedback on the program
=09structure, including orbit
=09utilization and the impact of
=09observing constraints

=A5=09powerful proposal diagnostics
=09based on access to the operational
=09STScI proposal support systems

New Phase II Template
The new Phase II proposal template eliminates the confusing and redundant aspects of the
old template and completely restructures the =D2special requirements=D3. The result is much
more readable and easy to use. A more subtle but important change is the shift from
=D2exposure logsheet=D3 to =D2target visit=D3 as the fundamental means for specifying usage of
HST.
In previous cycles, proposals were partitioned at STScI into clusters of exposures called
Scheduling Units (SUs) based on which exposures needed to be scheduled together. This
was done in a way that was largely opaque to observers. The implementation parameters
for some exposures were often dependent on those of other exposures in other SUs. As a
result, making even minor changes to a delivered program became very complex, especially
when part of it had already executed. Often the changed portion had to be split off into an
entirely different new proposal to effect the change.
Exposures in RPS2 proposals, however, are divided by proposers into visits, which will
correspond to the SUs in which they are scheduled. The internal structure of visits will be
completely independent; the implementation parameters of two exposures in separate visits
will never depend on each other. This will enable changes to be made with little difficulty,
even to proposals which have been partially executed.
Although the RPS2 template is significantly different from the RPSS template, there are
automatic tools which can perform the conversion. Cycle 5 observers interested in this
option should contact their Program Coordinators at STScI.

Access to STScI Software Systems
RPS2 provides transparent access to two STScI tools, SPIKE and TRANS, which will
allow observers to catch potential problems much earlier in the submission process than in
previous cycles. SPIKE has the ability to determine when during the Cycle portions of a
proposal can execute. Providing this information to observers before submission will make
it much easier for observers to make scientific trade-off decisions on the basis of more
accurate and relevant information.
TRANS determines implementation parameters for each proposal, and is often the earliest
place in which certain obstacles to a proposal=D5s execution can be identified. Providing HST
users this information will make it easier for them to create problem-free programs. Trans
also determines the overhead associated with exposures and can therefore tell when there
will be problems fitting observations within target visibility periods. Observers will now be
able to craft observations to fit within viewing intervals without the painful iteration of
phone calls and e-mail communication that used to characterize this p
rocess.
We expect that allowing observers access to TRANS will go beyond early detection of
problems. It will empower them to make their observations as efficient as possible. Now
that observing time is allocated by orbits, HST users will want to use all the available time
on target to maximize their scientific return. RPS2 provides graphical reports which enable
them to see quickly how much visibility has gone unused and where best to allocate the
extra time. In addition, the new Phase II format provides several new special requirements
which can be used to control this process and to construct programs whose efficiency is
robust to changes.

Graphical Feedback
The RPS2 software has user interfaces and reports that take advantage of computer
graphics capabilities, particularly to convey the results from TRANS and Spike. RPS2 was
constructed mostly using Tool Command Language (TCL), a modern scripting language
which is portable to many of the hardware platforms commonly used by HST observers for
data analysis. TCL has a built-in X-windows graphics library called TK, which allows
rapid development and easy maintenance of graphical user interfaces that will run on a
variety of platforms. Using TCL/TK, we will be able to distribute window-oriented
software to a majority of HST observers. This software will make it straightforward for
observers to connect, via a client/server link over the Internet, to powerful proposal
preparation tools at STScI.
Initial Release for Cycle 5
RPS2 will see its first operational use during Cycle 5, when observers will use it to prepare
their Phase II programs. Making it a success will require the cooperation of the entire HST
user community. We will need all the feedback we can get, both positive and negative, if
we are to turn RPS2 into a tool which will revolutionize HST proposal preparation. One of
the most important future developments will be a graphical user interface for editing RPS2
proposals, and suggestions about this in particular are encouraged.

=D1 Andy Gerb (STScI)

Improving HST Planning and Scheduling
During the course of a year, the HST executes tens of thousands of exposures of several
thousand targets. Many observations are linked to others via scientific =D2special
requirements=D3 specified by the observer in the proposal. All observations are subject to
numerous observing constraints such as Sun avoidance, occultation by the Earth, and
spacecraft roll and power constraints. At the beginning of the HST mission, planning and
scheduling work concentrated on the correct implementation and execution of observations.
In Cycles 2 and 3 a major effort to increase the productivity of the observatory (while
retaining quality) was begun which significantly increased HST observing efficiency. In
Cycles 4 and 5, a major effort is underway to further improve the planning and scheduling
process. Three main goals are:

=A5=09Improve the system=D5s flexibility
=09and responsiveness to change

=A5=09Provide a stable and accurate
=09Long-Range Plan (LRP)

=A5=09Increase visibility into the HST
=09observing schedule

Responsiveness
Prior to January 1994, the detailed observing program (called the Science Mission
Specification or SMS) was typically defined about 8 weeks in advance of execution. As a
result is was hard to make late changes, even when they were very well justified on
scientific grounds. Also, there were three or four subsequent weeks which could be
affected by a change, leading to rework of these schedules as well. For Cycle 4
observations, this 8 week lead time has been cut in half to 4 weeks, which makes it
possible to support later changes without impact and also means that only one or two
weeks will typically be affected by a change. Cycle 5 will see additional changes to increase
flexibility and change responsiveness (refer to the RPS2 article in t
his Newsletter).

Long-Range planning
 The long-range plan is an important tool for both the observer and the observatory staff.
The plan allows observations to be executed at near-optimal times while balancing the
needs of the overall science program. It allows observers and staff to plan their work and
can be an important analysis tool for assessing the effect of spacecraft and instrument
anomalies. HST long-range planning in earlier cycles allocated observations to a single
week during a Cycle. This strategy was unacceptably unstable, in that large numbers of
observations could not actually be scheduled in their planned week, a
nd thus had to be re-
planned. We have recently developed and tested a new technique for HST long-range
planning which retains the high quality and efficiency of current observations and provides
a stable plan. Observations are assigned =D2plan windows=D3 which are a subset of the
observing opportunities dictated by the scientific and spacecraft constraints. For most
observations, plan windows are 8 weeks in duration. We are currently phasing this new
technique into the telescope operations and will be making the long-range plan available to
the community (including access via the World-Wide Web).

Increased visibility into the Long Range Plan and Observing Schedule
 Another important goal is to provide observers with accurate and timely information on
their observing program and the observatory schedule. The weekly timeline is posted on
STEIS (http://www.stsci.edu/top.html) and also e-mailed to each Principal Investigator
with observations executing in that week. In August of this year, we introduced the World
Wide Web Program Information Page (http://presto.stsci.edu/propinfo.html) which is
described in a companion article in this Newsletter. This page gives 
accurate and up-to-the-
minute information on the execution status of the observing proposals. As the long range
planning procedures are developed and verified, we will make long range plan information
available through this interface. In addition, we are planning to develop tools which will
electronically mail important status and schedule changes to observer
s.

Integrated Approach to Planning and Scheduling
The PRESTO operations concept is based on an integrated approach to planning and
scheduling. Prior to the inception of PRESTO, planning and scheduling operations were
primarily the responsibility of the Science Planning Branch (SPB) in the Science Programs
Division and the Science Planning and Scheduling System (SPSS) Branch in the
Operations Division. When PRESTO was initiated in November 1993, it incorporated these
groups (and others) in order to promote a single team approach towards planning and
scheduling. Based on our experience since then, we have formed within PRESTO the
Science Planning and Scheduling Team (SPST), which is responsible for long range and
short term planning and scheduling. SPST works closely with other STScI groups such as
the Program Coordinator Team and Liaison Scientists and the software development teams.
An integrated approach to planning and scheduling software is also being pursued. Recent
advances in database technology have allowed us to quickly and reliably transfer
information between the long- and short-term scheduling systems. This has allowed us to
eliminate a number of time-consuming procedures and interfaces and to improve the quality
of observations and responsiveness to change. We are continuing the integration of these
systems in a number of other areas as well.
We welcome comments on the changes in progress and plans for the future. We also
welcome feedback on the current planning and scheduling process.

=D1 Glenn Miller (STScI)

HST Program and Schedule Information via WWW
In order to provide more complete and timely status information about HST programs, a
World Wide Web (WWW) accessible HST Program and Schedule Information page is
available via the STScI =D2Home Page=D3 (URL: http://www.stsci.edu/top.html) =D1 follow the
link under =D2Observer Information=D3 to =D2Program Status=D3 =D1 or directly at URL
http://presto.stsci.edu/public/propinfo.html.
To obtain the information about a specific program, enter the Proposal ID number (or
Program ID) in the field labeled =D2Program ID=D3 and click on the button labeled =D2Get
Program Information=D3.
If you don=D5t know the Program ID or have several programs, enter the PI=D5s last name in the
field labeled =D2PI=D5s Last Name=D3 and click on the button labeled =D2Find Programs=D3 (Fig. 1).
You will receive a page containing Program ID, PI Last Name, and Program Title(s) (Fig.
2). This search is case insensitive and tolerant of spelling mistakes.
Click on any Program ID to view the information page for that program (see Fig. 3). The
Proposal Information Page is generated directly from data drawn from the STScI
operational databases, kept up-to-date on a very short timescale. This page contains the PI
name and proposal title at the top, along with the overall program status. Note that clicking
on program status will bring up a page with more detailed explanation. How to contact
your program coordinator is given in the next line. The proposal file can be viewed either
as an RPSS (or RPS2) file, or as a formatted proposal listing, and you can search the
recent status reports for occurrences of the proposal.
Since a Program can have many visits, a separate Visit Status Information page is available
by clicking on =D2Visit Status Information=D3. The resulting page (see Fig. 4) contains, for each
visit, status and descriptive information, including the targets and instrument
configurations, and the time the visit was executed, or is scheduled 
to be executed.
This service is still quite new, and we welcome any feedback or suggestions for
improvement. You can e-mail any comments to hst_query@stsci.edu, or to your Program
Coordinator. A log of changes to this service is available at the URL
 listed above.

=D1 Bob Jackson (STScI)

Reporting Problems: HOPRs
We at the STScI are most interested in receiving feedback from you on the degree of
success of your HST Observations. Several years ago, the Hubble Observation Problem
Report or HOPR (pronounced =D2hopper=D3) was created to facilitate the reporting and tracking
of problems. HOPRs provide a mechanism for you to inform STScI when a problem has
occurred with the implementation, scheduling, execution, or data processing of your
observations. It is also the means by which Principal Investigators (PIs) make the request
for failed observations to be repeated.
Failed observations will be considered for rescheduling if an explicit request via a HOPR is
made by the PI. Note that observations which fail due to spacecraft or instrument safings,
or due to failure to acquire guide stars, are repeated automatically and do not need to have
HOPRs submitted. If a repeat observation is approved, the data associated with the failed
observation will generally be released as non-proprietary for public access. Requests to
repeat failed observations are reviewed by the STScI Telescope Time Review Board which
makes an investigation of the circumstances, assesses the impact of the request, and
forwards a recommendation to the STScI Director. We will notify PIs of the outcome of
this process, normally within a month of our receipt of the request. To allow us to address
the problems noted in HOPRs in a timely manner, the HOPR submission deadline for
requesting repeat observations is 3 months from the time of data dist
ribution.

Submitting HOPRs
At present, HOPRs are submitted on a form which is available from your Program
Coordinator, or you can request one via e-mail to hst_query@stsci.edu, or by phone at
(800) 544-8125. HOPRs may be submitted by postal mail (c/o Brett Blacker), or by FAX
to (410) 338-5085. We are investigating two additional options for HO
PR submission:

=A5=09via a form on the WWW

=A5=09direct e-mail submission

We expect to implement one or both of these mechanisms early in 1995, and will provide
information about them via the STScI WWW =D2Observer Information=D3 p
ages.

=D1Brett Blacker (STScI)

PRESTO Contact Points
General Information
Email: hst_query@stsci.edu

Phone: (800) 544-8125
(toll free, US only) or (410) 338-4452

Fax: (410) 338-5085

URL: http://www.stsci.edu/top.html
(general STScI)

http://presto.stsci.edu/public/propinfo.html
(observing program status)

Individual contacts:
Mark Johnston
PRESTO Project Lead
johnston@stsci.edu, (410) 338-4742

Glenn Miller
PRESTO Associate
Lead for Planning & Scheduling
miller@stsci.edu, (410) 338-4738

Peg Stanley
PRESTO Associate
Lead for Program Coordinators
pstanley@stsci.edu, (410) 338-4536

Doug McElroy
PRESTO Project Scientist
mcelroy@stsci.edu, (410) 338-4739

HOPR information and submission:
Brett Blacker
blacker@stsci.edu, (410) 338-1281


SOFTWARE AND DATA ANALYSIS NEWS
STSDAS NEWS
General
Version 1.3.2 of STSDAS was released on 1 August 1994 and contains a number of new
capabilities as well as bug fixes and improvements to existing tasks. Many of the changes
were described in the previous STScI Newsletter (April 1994, Vol. 11, No. 1) and in the
STSDAS Newsletter (available on-line =D1 see below for details =D1 or send us e-mail to get
on the distribution list). Some of the highlights of our current software development
projects are described in more detail below.
A major effort has gone into improving our ability to detect and reject cosmic rays in
images. A new task called =D2gcombine=D3 is a general-purpose utility for combining two or
more images while excluding masked pixels and robustly rejecting outlier values. This task
is in many ways similar to the IRAF =D2imcombine=D3 task, in that there are a variety of
algorithms for rejecting outlier values, and for scaling, weighting, and combining the
remaining values. The chief differences are that =D2gcombine=D3 offers additional options for
robust rejection of outliers, it can combine multi-group images, and it can weight the input
pixel values more appropriately (and more flexibly). In particular, =D2gcombine=D3 can weight
and scale images according to: input image exposure time; the mean, median, or mode of an
image section; values of header keywords; optional input =D2variance=D3 images; or according
to a user-supplied list of values. An example of the results of this task is shown in Figure
1, in which a combination of three 2 sec and three 40 sec exposures of the Eta Carinae
nebula (images courtesy R. White) allows one to mask saturated and hot pixels and exclude
cosmic rays. A paper describing in detail the methodologies of this task will appear in the
ADASS IV Conference Proceedings (Zhang 1995, ASP Conf. Series, in pre
paration).
Both WFPC-1 and WFPC-2 have internal geometric distortions and misalignments in the
detectors that make it impossible to simply patch the CCD frames together to form a single
image. The =D2wmosaic=D3 task supports the proper alignment and mosaicing of WFPC-1
images, incorporating knowledge of the alignments and the intrinsic geometric distortions
of the detectors. The next patch release of STSDAS (due in early 1995) will include the
support for WFPC-2 frames that has recently been added. An example of a WFPC-2
mosaic which includes a star image at the intersection of the four CCDs is shown in Figure
2.
Both the FOS and HRS pipelines have seen major improvements. CALFOS now includes
aperture and sensitivity corrections for pre-COSTAR data, and calibrations are now based
on standard white dwarf spectral energy distribution models. FOS and HRS observers
should contact either the STSDAS Group or the Instrument Scientists for more details and
for advice on recalibration.
It is now possible to correct FOS spectra for the scattered light using the task =D2bspec=D3. Staff
at the ST-ECF (M. Rosa and Th. Mueller) developed this facility for MIDAS, and the
program and additional tools have been implemented in STSDAS. Using an input model
spectrum, =D2bspec=D3 computes the scattered light expected for a specified FOS grating and
aperture. An example is shown in Figure 3 for the G5V star 16 Cyg B, where it is clear that
the scattered light model gives excellent agreement with the observed data (the observed
spectrum is offset vertically from the model for the sake of clarity). A more detailed
explanation of the task is available in the help file and in a paper to be published in this
year=D5s ADASS Conference Proceedings (Bushouse, Rosa, and Mueller 1995, ASP Conf.
Ser., in preparation).

STSDAS On-Line Services
Much of the documentation related to STSDAS is now available on the World Wide Web
(the URL is http://ra.stsci.edu/STSDAS.html). The STSDAS User=D5s Guide is now
available in hypertext, and many items appear as links to the help files or other documents.
=46rom the STSDAS home page you can also contact the STSDAS Hotseat, retrieve the
software, or jump to the home pages for IRAF, PROS, and the ADASS Conferences.
Another very useful facility is the WAIS index of all STSDAS documentation and all SPP
source code. You simply enter keywords of interest, and the system finds the documents
most likely to contain information about tasks or subroutines relevan
t to your keywords.

Plans and Prospects
At this time the STSDAS Group is beginning to focus its attention on the development of
calibration software for STIS and NICMOS. We have begun working with the instrument
developers to understand the calibration requirements and have already made progress in
the design of data structures. We are planning to make extensive use of the STSDAS
Tables facility, with extensions to accommodate arrays stored in table column entries, for
the extracted spectra from STIS (flux arrays, wavelength arrays, and associated weighting
or bad pixel arrays). STSDAS Tables have a rich suite of applications (see the =D2ttools=D3
package for examples) and should prove an excellent format for STIS s
pectra.
We are also moving forward with the implementation of various aspects of the =D2Open
IRAF=D3 project. The various groups working in the IRAF environment (
NOAO, SAO, UC-
Berkeley/EUVE, etc.) have jointly developed a plan to make the IRAF system more open,
that is:

=A5=09Provide full system support for
=09programming in standard
=09languages (C, Fortran,
=09and possibly C++).

=A5=09Make it easier to run IRAF tasks
=09independent of the IRAF CL.

=A5=09Enable use of specific packages or
=09tasks without having to install the
=09entire system.

=A5=09Explore options for making IRAF
=09applications available as network
=09services.

In addition, we are investigating the feasibility of calling subroutines written in C and
layered on IRAF I/O functions from external environments such as IDL. We realize that a
significant number of HST observers use IDL, and we wish to be able to provide our new
calibration software in such a way as to make it usable from within both the IRAF and IDL
systems. Our first experiments along these lines will be for the STIS and NICMOS
calibration pipelines.
In summary, there are major challenges ahead for the STSDAS Group, both in terms of
applications software development for STIS and NICMOS and in the area of systems
development. Budgetary pressures are forcing us to limit our work in more generic data
analysis applications, but we believe that we will be able to provide excellent facilities for
HST calibration, including support for users both within and outside the IRAF
environment, in the coming years.
If you have any questions about STSDAS/IRAF please contact us through our user support
hotline (e-mail: hotseat@stsci.edu).

=D1 Bob Hanisch and Dick Shaw (STScI)

ADASS CONFERENCE
The STSDAS Group was the local host for the 1994 Astronomical Data Analysis Software
and Systems (ADASS) Conference, which was recently held at the Omni Inner Harbor
Hotel in Baltimore on 25-29 September. The conference was attended by over 300 people
and featured invited talks in the areas of networking, user interface design, high
performance computing, and data modelling. Special interest meetings were also held on
the topics of FITS, IDL, and IRAF, and there were 15 software demonstrations and 93
poster presentations. The Proceedings of the Conference are now in preparation and are
planned to be made available electronically as well as in a forthcoming volume in the ASP
Conference Series. The Proceedings of ADASS III (Victoria, BC) were published this fall
in the ASP Conference Series, Volume 61.
ADASS IV was a great success! ADASS V is now being planned and will be held in
Tucson on 22-25 October 1995. Everyone with an interest in astronomical software is
invited to attend.

=D1 Bob Hanisch
(STScI; Chair, ADASS Program Organizing Committee)

DIGITIZED OPTICAL SKY SURVEYS AT STScI
Recent Developments
The program to compress 1541 digitized Schmidt plates covering the entire sky is now
complete. Details of the program, including a description of the plate material and the
algorithms used may be found in previous Newsletters, and similar material is being posted
on our WWW server (see below). The plates were digitized using the STScI scanning
microdensitometers with a pixel size of 25 microns square (1.7"); all the scans have
undergone extensive quality assurance checks.
Two versions of the entire sky have been produced =D1 one at a compression factor of 10
which is virtually indistinguishable from the original data, and one at a compression factor
of about 100 which, while not suitable for professional research activity, will provide an
invaluable tool for the educational and amateur communities. The Astronomical Society of
the Pacific (ASP) is responsible for the distribution of the 10x compressed data. The south
was distributed to the subscribers in May 1994, and the north will be distributed in late
December 1994 or early January 1995.
A first version of the photometric calibration database will be published in the summer of
1995. This will be based on existing photometric calibration sequences and will allow
stellar photometry to be performed to a limit of the GSC (V~15). An advanced photometric
calibration, based on deeper CCD calibration sequences (V~18), is planned as a subsequent
version.
Distribution plans for the 100x digitized sky survey data are currently under development,
with a publication goal sometime in 1995. The targets groups are educational institutions
and the amateur astronomy community, as well as the general public. Software to access
the compressed sky survey data in a user friendly manner on PCs and Macs exists and will
shortly be available from ASP. A series of lesson plans which use the digitized sky survey
are being developed by staff at the STScI and the ASP.

The Second-Generation Scanning =D1 Technical Status
Digitization of the 3576 plates which constitute the second Palomar Sky Survey and the
new red surveys made with the UK Schmidt continues; background, details, and a list of
plates may be found in the April 1994 Newsletter. Supporting this, system modifications to
the first of two CASB microdensitometers, GAMMA-1 (GSSS Automated Measuring
Machine), were essentially completed in the summer. Work on the second machine,
GAMMA-2, together with a low level of clean-up in the areas of focus robustness,
maintainability, and reliability, is currently in progress. The throughput of the GAMMA
system was verified by scanning three plates in a continuous 23 hour interval in August;
this rate, implemented with proper staffing (see below) on two machines, and with
reasonable allowances for contingencies, amounts to a capability in excess of 1000 plates
per year. Projecting from the present status of about 500 second-generation scans, we thus
expect to complete the scanning in 1998.
Preliminary experiments regarding the selection of a compression factor for the ultimate
distribution of the second-generation scans on CD ROM indicate that 10X (the same as in
the previous distributions) is appropriate. A future Newsletter will give further results on
these studies as well as on data-organization issues, and will solicit community input on the
CD ROM distribution.

Programmatic Issues
The adjustments required by the STScI FY=D595 budget necessitated a number of changes in
the plans and activities for the Catalogs and Surveys Branch (CASB): (a) improved
calibrations of the Guide Star Catalog (GSC 1.2 and beyond), while remaining a scientific
goal, are no longer a supported project, (b) the development of export software to be used
in conjunction with the Digital Sky Survey is no longer being developed in
STSDAS/IRAF, and (c) the operations staff for plate scanning was lowered to a minimal
level (i.e., less than one full person).
While the first two of these may conceivably be addressed with new collaborations or
alternative technical approaches, the reduced staffing level for plate scanning is a major
obstacle to completing the second generation scanning in a timely manner, if at all. At the
present staffing level, the annual throughput is unlikely to exceed 300-400 plates per year.
Therefore, two steps are being taken to give the scanning a more solid programmatic basis
and to broaden its support, particularly internationally. First, proposals are now being
prepared for U.S. funding outside the NASA HST Project. Second, Patrons of the
scanning project are being sought; these will receive prepublication scan data in return for
their contribution to the financial support of the project. In the near-term, it is gratifying to
report that funds from the first Patron will soon be available to hire part-time operators on
the second shift and on weekends.

The CASB Homepage and
Mosaic Services
In order to provide information beyond that occasionally furnished in these Newsletters,
the CASB has implemented an http server for World Wide Web (WWW) access. This
server currently provides information about CASB, the Digitized Sky Survey (DSS),
sample images from the DSS, updates on the GetImage software for the DSS, access to the
Guide Star Catalog (GSC), and the status of the second-generation scanning program;
additionally access to the DSS is under development.
The current URL is http://www-gsss.stsci.edu; alternately one may follow the link from the
STScI homepage.
We shall use future Newsletters and the WWW server to keep the community informed
about progress in the various CASB activities. Correspondence about CASB should be
addressed to lasker@stsci.edu.

=D1Barry Lasker (STScI)


INSTITUTE NEWS
SYMPOSIA AND WORKSHOPS
The annual 1994 STScI May Symposium on The Analysis of Emission Lines, A Meeting
in Honor of the 70th Birthdays of D.E. Osterbrock and M.J. Seaton, was held at the
Institute on 16-18 May with over 180 participants. The meeting covered all aspects of the
analysis of emission lines in different wavelength bands. The invited speakers were: L.
Woltjer (Historical Perspective), A. Pradhan (Atomic Data & Cross Sections), D. Hummer
(Radiative Transfer), M. Dopita (Shocks), G. Ferland (Photoionization), P. Pinto
(Expanding Atmospheres), K. Horne (Eclipse Mappings, Doppler Tomography), R.
Mushotzky (X-Ray Plasmas), H. Dinerstein (IR Spectroscopy), A. Dalgarno (Molecular
Line Diagnostics), M. Peimbert (Abundances), R. Dufour (UV Spectroscopy), J. Drew
(Winds), H. Netzer (Line Diagnostics), R. Ramaty (Gamma Ray Spectroscopy), J. Miller
(Spectropolarimetry), and V. Trimble (Conference Summary). Short contributions were
presented in the form of posters. The proceedings will be published by Cambridge
University Press.
The STScI also hosted two mini-workshops. One, on Dust Survival in
Interstellar/Intergalactic Media took place on 13-15 July and concentrated on processes of
dust formation and destruction. The second mini-workshop, on Quantifying Galaxy
Morphology at High Redshift, was held in April 1994, and it focused on quantitative
methods of classification of galaxy morphology.
The title of the 1995 May Symposium is The Collision of Comet P/Shoemaker-Levy 9 and
Jupiter. The Symposium, hosted by the STScI and The Johns Hopkins University, will be
held on 9-12 May 1995. Please see the accompanying announcement for further
information and note that, due to the large expected attendance, you must apply for an
invitation (first-come, first-serve) if you want to participate.

=D1 Mario Livio (STScI)

ESA FELLOWSHIPS AT STScI
Astronomers of ESA member countries are reminded of the possibility of coming to do
research at STScI as an ESA Fellow. Prospective fellowship candidates should aim to
work with a particular member or members of the staff at STScI, and for this reason,
applications must be accompanied by a supporting letter from STScI.
Details of the interests of staff members at STScI can be obtained from Dr. Nino Panagia
(panagia@stsci.edu). Details of the fellowships and applications procedures can be
obtained from the EDUCATION OFFICE, ESA, 8-10 rue Mario Nikis, 75738 PARIS 15,
FRANCE. Completed application forms must be submitted through the appropriate national
authority and should reach ESA no later than 31 March for consideration in May, and no
later than 30 September for consideration in November. A copy of the completed
application should be sent to the Chairman of the Postdoc Selection Committee (currently
Dr. Michael Fall) at STScI, 3700 San Martin Drive, Baltimore, MD 21218, USA. Selected
Fellows must negotiate the commencement dates of their ESA Fellowships at STScI with
the University Programs Division (c/o Dr. Ron Allen) at least 2 months before their
prospective starting times. The interests and activities of staff members at STScI can best
be assessed by reading the annual report of the Institute, which can be found in the Bulletin
of the American Astronomical Society (1994) Vol. 26, p. 617. Currently there are two ESA
Fellows in residence at STScI, Salvatore Scuderi, who is studying stellar winds and
supernovae, and Nicola Caon, whose interests are elliptical galaxies 
and jets.

=D1Nino Panagia (STScI)

HUBBLE FELLOWSHIP PROGRAM
The Announcement of Opportunity for the sixth round of competition for Hubble
Postdoctoral Fellowships was issued at the beginning of September 1994. The deadline for
submitting applications was 11 November. The applications received by that time will be
considered by the Review Panel that meets in late January 1995. Offers to succesful
candidates will be made by 1 February 1995. Further information on the Hubble
Fellowship Program can be obtained from        Howard Bond (410-338-4718, or
bond@stsci.edu).
On 24-25 October 1994, the current Hubble Fellows met at the STScI for the Fourth
Hubble Symposium to present the results of their Hubble Fellowship research projects. As
usual, many interesting topics were discussed that demonstrate the vitality of this unique
program.

=D1 Nino Panagia (STScI)

SABBATICAL VISITORS AT STScI
In order to promote the exchange of ideas and collaborations in HST-related science, STScI
expects to provide limited funds to support visiting scientists who wish to spend extended
periods of time (typically three to six months) doing research at STScI. Typically the visitor
is on sabbatical leave from his or her home institution. In general, these visitors will have
the status of STScI employees and have access to the facilities available to staff members.
Established scientists who might be interested in such a visit during the summer of 1995 or
during the academic year commencing in September 1995 should send a letter specifying
the suggested period for the visit and any other relevant details to the Visiting Scientist
Program, c/o Nino Panagia (e-mail panagia@stsci.edu) at STScI. Applicants should also
include a statement of research plans and a copy of their curriculum vitae. The deadline for
receipt of applications is 1 February 1995.

=D1 Nino Panagia (STScI)

GRADUATE STUDENT
RESEARCH ASSISTANTSHIPS

The Space Telescope Science Institute invites applications from advanced graduate students
to pursue Ph. D. thesis-level research with members of the Institute staff. The scientific
fields represented at the Institute cover much of modern astronomy, including theoretical,
observational, and instrumental programs. Since STScI is not a degree-granting
organization, all students must be enrolled in the graduate program at their home university.
Applicants should have a bachelors degree, should have completed all required graduate
course work, and should have been admitted to the Ph. D. program at their home
university, which must give permission for them to work at STScI.
The program is intended for students who will spend at least one year at the Institute, but
proposals for shorter visits will also be considered. Applications from students at both
U.S. and foreign institutions are invited.
Applications for this program should be sent to the Personnel Manager, Space Telescope
Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA and should be
clearly marked =D2Graduate Student Program=D3. They should include a curriculum vitae, a
statement of research interests, and a letter from their advisor or departmental chairperson
giving permission for them to work at STScI. Applicants should arrange for all their
academic transcripts and three letters of recommendation to be sent directly to the Personnel
Manager. The deadline for receipt of applications is 1 March 1995. For further information,
please contact Michael Fall at the Space Telescope Science Institute 
(e-mail fall@stsci.edu).

RECENT STScI PREPRINTS
826. =D2Cooling of the White Dwarf in U Geminorum between Outbursts,=D3 K.S. Long,
E.M. Sion, M. Huang, P. Szkody

827. =D2New HST Observations of the Core of R Aquarii I. Imaging,
=D3 F. Paresce, W. Hack

828. =D2Cataclysmic Binaries in Star Clusters. I. A Search for Erupting Dwarf Novae in the
Globular Cluster M92,=D3 M.M. Shara, L.E. Bergeron, A.F. J. Moffat

829. =D2The Photometric Properties of the HST Astrometer Fine Guidance Sensor,=D3 B.
Bucciarelli, S.T. Holfeltz, M.G. Lattanzi, L.G. Taff, P.C. Vener-Saav
edra

830. =D2Dynamics and X-Ray Emission of a Galactic Superwind Interacting with Disk and
Halo Gas,=D3 A.A. Suchkov, D.S. Balsara, T. M. Heckman, C. Leitherer

831. =D2A Large, Periodic Variation in the Stellar Wind of q1 Orionis C,=D3 N.R. Walborn,
J.S. Nichols

832. =D2Nonthermal Pair Models, Reflection, and X-Ray Spectral Variability of Active
Galaxies,=D3 P. Grandi, C. Done, C.M. Urry

833. =D2A Dwarf Nova in the Core of 47 Tucanae,=D3 F. Paresce, G. De 
Marchi

834. =D2Atmospheric Parameters of Field Sub-dwarf B Stars,=D3 R.A. Saffer, P. Bergeron, D.
Koester, J. Liebert

835. =D2Disk-Resolved Imaging of Io with the Hubble Space Telescope,=D3 P. Sartoretti, M.A.
McGrath, F. Paresce

836. =D2A Survey for Highly Variable Objects on the SRC J Plates. I. Faint New
Cataclysmic Variables in the Galactic Halo,=D3 L. Drissen, M.M. Shara, M. Dopita, D.T.
Wickramasinghe

837. =D2The Distribution and the Nature of Star Formation Regions in NGC 1792,=D3 M.
Dahlem, D.J. Bomans, J-M. Will

838. =D2Soft X-Ray Observations of the Interacting Galaxies NGC 1808 and NGC 1792,=D3
M. Dahlem, G.D. Hartner, N. Junkes

839. =D2Hubble Space Telescope Fine Guidance Sensor Interferometric Observations of the
3
Core of 30 Doradus,=D3 M.G. Lattanzi, J.L. Hershey, R. Burg, L.G. Taff, S.T. Holfeltz, B.
Bucciarelli, I.N. Evans, R. Gilmozzi, J. Pringle, N.R. Walborn

840. =D2The Ultraviolet Pulsations of the Cataclysmic Variable AE Aquarii As Observed with
the Hubble Space Telescope,=D3 M. Eracleous, K. Horne, E.L. Robinson, E-H. Zhang,
T.R. Marsh, J. Wood

841. =D2Multicolor Eclipse Studies of UU Aqr. I. Observations and System Parameters,=D3 R.
Baptista, J.E. Steiner, D. Cieslinski

842. =D2A Direct Way to Measure the Distances of Galaxies,=D3 W.B. Sp
arks

843. =D2The Analysis of Star Catalogs: I. An Inter-Comparison among the FK3, the FK4,
and the FK5,=D3 B. Bucciarelli, M.G. Lattanzi, L.G. Taff

844. =D2The Analysis of Star Catalogs: II. An Inter-Comparison among the GC, the N30,
and the FK5(B1950.0/FK4),=D3 L.G. Taff, B. Bucciarelli

845. =D2On the Fate of Accreting White Dwarfs in Cataclysmic Variables and Related
Systems,=D3 M. Livio

846. =D2High Rydberg State Carbon Recombination Lines toward Cas A: Physical
Conditions and a New Class of Models,=D3 H.E. Payne, K.R. Anantharamaiah, W.C.
Erickson

847. =D2High Rydberg State Carbon Recombination Lines toward Cas A: 332 Mhz VLA
Observations and Comparison with HI and Molecular Lines,=D3 K.R. Anantharamaiah, W.C.
Erickson, H.E. Payne, N.G. Kantharia

848. =D2Impact-Driven Eccentricity in Accretion Disks,=D3 S.H. Lubow

849. =D2Hubble Space Telescope Imaging of the Seyfert 2 Galaxy NGC 2110,=D3 J.S.
Mulchaey, A.S. Wilson, G.A. Bower, T.M. Heckman, J.H. Krolik, G.K. Mi
ley

850. =D2Galaxies in Clusters: Gas Stripping and Accretion,=D3 D. Balsara, M. Livio, C.P.
O=D5Dea

851. =D2The Radio Emission from the Ultra-Luminous Far-Infrared Galaxy NGC 6240,=D3
E.J.M. Colbert, A.S. Wilson, J. Bland-Hawthorn

852. =D2Multiwavelength Tests of the Dusty Torus Model for Seyfert Galaxies,=D3 J.S.
Mulchaey, A. Koratkar, M.J. Ward, A.S. Wilson, M. Whittle, R.R.J. Antonucci, A.L.
Kinney, T. Hurt

853. =D2On the Effects of Tidal Interaction on Thin Accretion Disks: An Analytic Study,=D3 R.
Dgani, M. Livio, O. Regev

854. =D2The Solar Neighborhood I: Standard Spectral Types (K5 to M8) for Northern
Dwarfs within Eight Parsecs,=D3 T.J. Henry, J.D. Kirkpatrick, D.A. Si
mons

855. =D2The Effect of the Cluster Environment on Galaxies,=D3 B.C. Wh
itmore

856. =D2The Butcher-Oemler Effect in Radio Selected Groups of Galaxie
s,=D3 E. L. Zirbel

857. =D2Properties and Variability of the Stellar Wind from P Cygni ,=D3 S. Scuderi, G.
Bonanno, D. Spadaro, N. Panagia, H.J.G.L.M. Lamers, A. De Koter

858. =D2The Unified Seyfert Scheme and the Origin of the Cosmic X-Ray Background,=D3 P.
Madau, G. Ghisellini, A.C. Fabian

859. =D2Elliptical Accretion Disks in Active Galactic Nuclei,=D3 M. Eracleous, M. Livio, J.P.
Halpern, T. Storchi-Bergmann

860. =D2A Ring Nebula Surrounding Evolved Massive Stars in the Post-Starburst Galaxy
NGC 1569,=D3 L. Drissen, J-R. Roy

861. =D2The Difference between Radio-Loud and Radio-Quiet Active Galaxies,=D3 A.S.
Wilson, E.J.M. Colbert

862. =D2Markarian 315: A Test-Case for the AGN-Merger Hypothesis?=D3 J.W. MacKenty,
S.M. Simkin, R.E. Griffiths, J.S. Ulvestad, A.S. Wilson

863. =D2Synthetic Properties of Starburst Galaxies,=D3 C. Leitherer, 
T.M. Heckman

864. =D2The He II Lyman-alpha Opacity of the Universe,=D3 P. Madau, A
. Meiksin

865. =D2Galaxies with Extreme IR and Fe II Emission. II. IRAS 07598+6508 A
Starburst/Young BAL-QSO,=D3 Sebastian Lipari

866. =D2Dwarf Elliptical Galaxies,=D3 H.C. Ferguson, B. Binggeli

867. =D2Absolute Flux Calibration of Optical Spectrophotometric Standard Stars,=D3 L. Colina,
R.C. Bohlin

868. =D2Interacting Binary Galaxies. VII. Kinematic Data for 12 Disturbed Ellipticals,=D3 K.D.
Borne, M. Balcells, J.G. Hoessel, M. McMaster

869. =D2Globular Cluster Photometry with the Hubble Space Telescope. III. Blue Stragglers
and Variable Stars in the Core of M3,=D3 P. Guhathakurta, B. Yanny, J.N. Bahcall, D.P.
Schneider

870. =D2Discovery of Cepheids in NGC 5253: Absolute Peak Brightness of SNe Ia 1895B
and 1972E and the Value of H0,=D3 A. Saha, A. Sandage, L. Labhardt, H. Schwengeler,
G.A. Tammann, N. Panagia, F.D. Macchetto

871. =D2HST/FOC Imaging of the Narrow-Line Region of NGC 1068,=D3 F. Macchetto, A.
Capetti, W.B. Sparks, D.J. Axon, A. Boksenberg

872. =D2Detection of Extended HI Absorption towards PKS 2322-123 in Abell 2597,=D3 C.P.
O=D5Dea, S.A. Baum, J. Gallimore

873. =D2Low Luminosity Active Galaxies: Are They Similar to Seyfert Galaxies?=D3 A.
Koratkar, S.E. Deustua, T. Heckman, A.V. Filippenko, L.C. Ho, M. Rao

874. =D2The Contribution of Low Surface-Brightness Galaxies to Faint Galaxy Counts,=D3
H.C. Ferguson, S.S. McGaugh

875. =D2Extended Soft X-ray Emission in Seyfert Galaxies: ROSAT HRI Observations of
NGC 3516, NGC 4151 and Markarian 3,=D3 J.A. Morse, A.S. Wilson, M. Ellis, K.A.
Weaver

876. =D2UV to Optical Spectral Distributions of Northern Star-Forming Galaxies,=D3 K.
McQuade, D. Calzetti, A.L. Kinney

877. =D2Radiative Transfer in a Clumpy Universe: The Colors of High Redshift Galaxies,=D3
P. Madau

878. =D2Ultraviolet to Near-Infrared Spectral Distributions of Star-Forming and Seyfert 2
Galaxies,=D3 T. Storchi-Bergmann, A.L. Kinney, P. Challis

879. =D2In-Orbit Performance of the COSTAR-Corrected Faint Object Camera,=D3 R.I.
Jedrzejewski, G. Hartig, P. Jakobsen, J.H. Crocker, H.C. Ford

880. =D2Cataclysmic and Close Binaries in Star Clusters. II. Probing the Core of NGC 6752
with HST,=D3 M.M. Shara, L. Drissen, L.E. Bergeron, F. Paresce

881. =D2Very Low Mass Stars and White Dwarfs in NGC 6397,=D3 F. Paresce, G. De Marchi,
M. Ramaniello

882. =D2A High Spectral Resolution VLA Search for HI Absorption towards A496, A1795,
and A2584,=D3 C.P. O=D5Dea, J.F. Gallimore, S.A. Baum

883. =D2The Variability of the Double-Peaked Balmer Lines in the Active Nucleus of NGC
1097,=D3 T. Storchi-Bergmann, M. Eracleous, M. Livio, A.S. Wilson, A.V. Filippenko,
J.P. Halpern

884. =D2The Discovery of Five New H2O Megamasers in Active Galaxies,=D3 J.A. Braatz,
A.S. Wilson, C. Henkel

885. =D2HST Imaging of a Radio-Quiet Galaxy at Redshift Z==3.4,=D3 M. Giavalisco, F.D.
Macchetto, P. Madau, W.B. Sparks

RECENT STAFF CHANGES
MICHAEL A=D5HEARN, a Sabbatical Visitor in UPD from the University of Maryland,
began his stay at the Institute in September.

KEN ANDERSON, former Technical Assistant II in PRESTO/USB, left the Institute this
summer.

LUC BINETTE joined the Institute in September as a Research Associate in UPD. Luc was
previously an Assistant Professor at Canadian Institute for Theoretical Astrophysics in
Toronto, Ontario.

BEATRICE BUCCIARELLI, former Research Associate in SCARS/CASB, left the
Institute this summer.

Stefano Casertano, ESA, will be working as a WFPC-2 Instrument Scientist on issues
related to monitoring the photometric performance of WFPC-2, and improving the
calibration and reduction of data. His previous position was as an Associate Research
Scientist at The Johns Hopkins University in the Center for Astrophysical Science; he
worked for the WFPC-2 IDT team and collaborated with the Medium-Deep 
Survey group.

Michael Dahlem, ESA, joined the Institute as an FOS Instrument Scientist. His field of
research is interstellar matter in disks and halos of nearby galaxies. Previously, he was
working as a post doc at Johns Hopkins University, working on ROSAT observations of
starburst galaxies.

SIGRID DE KOFF joined the SPD/SIB Institute staff in September. Sigrid is a Graduate
Student working on her Ph.D.

PETER EDMONDS, formerly a Senior Research Assistant at the University of Sydney=D5s
Research Centre for Theoretical Astrophysics in Sydney, Australia, joined the staff of
SPD/SIB in April as a Postdoctoral Fellow. He is currently working on WFPC-1
observations of the globular cluster 47 Tuc with Ron Gilliland.

THOMAS GAENG joined the SPD/SIB Institute staff in August. Thomas is a Graduate
Student working on his Ph.D.

RACHEL GIBBONS, a Graduate Student in SCARS/DSOB, joined the Institute in
September. Rachel was previously a Research Assistant at Goddard Spac
e Flight Center.

Roberto Gilmozzi, an ESA Astronomer, left the Institute at the end of August 1994. He is
currently working at ESO headquarters in Germany on VLT programs.

ROBERT GOODRICH joined the SPD/SIB Institute staff in September. Robert is a
Postdoctoral Fellow who was previously a Postdoc at Lick Observatory. He is currently
working on FOS polarimetry and normal spectroscopy of quasars with Anne Kinney and
Anuradha Koratkar.

FRANCESCO HAARDT, former Graduate Student in SPD/USB, left the Institute in
September.

HASHIMA HASAN, Associate Scientist in SPD/SOB, is on a leave of absence until
August 1995. She has joined NASA HQ as a visiting senior scientist in the UV/Visible
branch of the Astrophysics Division.

DESTINIE JONES, former Technical Assistant I in PRESTO/SPB, left the Institute this
summer.

KIRK KORISTA, former Postdoctoral Fellow in SPD/SIB, left the Institute in July. He is
currently in the department of Physics and Astronomy at the Universit
y of Kentucky.

SEBASTIAN LIPARI, former Postdoctoral Fellow in SPD/Division Office, left the
Institute in August.

PHILLIP MARTELL, former Postdoctoral Fellow in UPD, left the Institut
e in May.

KERRY MCQUADE, former Science Data Analyst I in SCARS/RSB, left the Institute this
summer.

DANA MITCHELL was promoted to Chief, ESB in SESD/ESB in July.

JOHN MULCHAEY, former Graduate Student in UPD, left the Institute in 
September.

Charles Nelson joined the Institute in September 1994 as a Postdoctoral Fellow. He is
analyzing HST snapshots of a sample of Markarian galaxies in collaboration with John
MacKently. He was previously a graduate student at the University of Virginia and finished
his thesis in August.

ANNA PASQUALI, former Graduate Student in SPD/SOB, left the Institute
 in August.

MIRIANI PASTORIZA began her stay at the Institute as a Sabbatical Visitor in April.
Miriani has joined the staff in UPD.

DIEGO PEREZ-OLEA, a Graduate Student Research Assistant, joined the SPD/SOB staff
in June. Diego is working on his Ph.D. thesis in the Department of Theoretical Physics at
the Universidad Autonoma de Madrid in Spain.

DINA PRIALNIK-KOVETZ, former Sabbatical Visitor in UPD, left the Institute in
August.

MAYA RAO, former Science Data Analyst I in SCARS/RSB, left the Instit
ute in July.

PETE REPPERT, former Technical Assistant II in PRESTO/USB, left the Institute this
summer.

BRIAN ROSS, former Systems Engineer in SESD/SEB, left the Institute t
his summer.

MAITRAYEE SAHI, former Science Data Analyst II in SCARS/RSB, left the Institute this
summer.

KAREN SCHAEFER began her appointment as a Postdoctoral Fellow in UPD in March
working with Howard Bond. Karen was previously in the NASA Graduate Student
Researchers Program at Goddard Space Flight Center.

JAMES SCOTT, former Science Data Analyst I in SCARS/RSB, left the Institute this
summer.

LISA SICILIANO, former Photometry Analyst in SCARS/CASB, left the Institute in
September.

DAVID SILBERBERG, former Senior Computer Scientist in SESD/OSB, left the Institute
this summer.

Christopher Skinner, ESA, is currently working on NICMOS, one of the advanced Science
Instruments to be deployed on the 1997 Servicing Mission. Previously, he was at the
Institute of Geophysics & Planetary Physics at Lawrence Livermore Laboratory, where he
was working on near-infrared and mid-infrared imaging and spectroscopy of evolved stars
and Vega-excess stars.

RICKEY SMART, former Postdoctoral Fellow in SCARS/SOB, left the Institute in
September.

JIM SOKOLOWSKI, former Post-
doctoral Fellow in SPD/SIB, left the Institute in August.

LARRY TAFF, former Associate Scientist and FGS Instrument Scientist in SCARS/SOB,
left the Institute in September.

CINDY TAYLOR, former Technical Assistant II in SPD/SIB, left the Institute in August to
study for a Ph.D. in astronomy at Dartmouth College.

PATRICIA VADER, former Associate Astronomer in UPD/SPSO, left the Institute this
summer.

FABIENNE VAN DE RYDT, former Science Data Analyst II in SCARS/RSB, left the
Institute in June.

YUBO WANG, Engineering Assistant in SESD/ESB, returned to the Institute in
September. Yubo was recently a Summer Research Assistant at the Insti
tute.

NAILONG WU, former Technical Assistant in SCARS/SSB, left the Institute in
September.

FANG ZHOU, former Graduate Student in SPD/SIB, left the Institute in 
August.

DAVID ZUREK joined the Institute in May as a Science Data Analyst in UPD/SPSO.
David was previously a Research Assistant in the Department of Physics and Astronomy at
the University of Victoria.

HOW TO CONTACT ST ScITelephone: 410-338-4700
(reception); 410-338 + 4-digit extension of staff member
Fax: 410-338-4767
Mail: =09STScI
=093700 San Martin Drive
=09Baltimore, MD 21218
=09USA
E-mail: Most staff members at ST ScI can be reached on NSI/DECnet and Internet.
Address formats are:
NSI/DECnet: stscic::userid=09=09or 6559::userid
Internet:=09userid@stsci.edu

STScI is no longer directly on BITnet. Users in BITnet must therefore send e-mail through
a gateway to the Internet. One possible way is by using the address format:

userid%stsci.edu@internet

With few exceptions the userid is the staff member=D5s surname. Many are published in the
Membership Directory of the American Astronomical Society. If you do not know the
userid, please send the mail to the User Support Branch (userid USB), which will forward
it.