STScI NEWSLETTER March 1993 

HST SCIENCE HIGHLIGHTS

A LARGE NUCLEAR ACCRETION DISK IN NGC 4261
During a survey of a complete sample of elliptical galaxies in the Virgo Cluster (Jaffe et al. 1993) we 
took two F555W exposures of 1700s and 700s of NGC 4261 with the Planetary Camera. Cosmic rays were 
removed by combining the images with the STSDAS task combine. We used Lucy deconvolution and 
Fourier filtering to improve the contrast in the original image. Both images showed the same features, all 
of which can be seen in the unsharpened image, albeit with lower contrast. 
A smooth absorbing disk with sharp edges and a point-like nucleus is visible. The disk is elliptical, with 
axes of ~ 1.7" by ~ 0.7". Assuming the disk is intrinsically circular, the plane of the disk is inclined 
64 degrees� to the plane of the sky.
We assume that the distance to NGC 4261, which is in the �Virgo West� cloud, is that of the Virgo 
Cluster, 14.7 Mpc (Jacoby et al. 1990). The diameter of the disk is then ~ 120 pc. If the Virgo West cloud 
is at about twice the distance to the main Virgo cluster as assumed by many workers, the physical 
dimensions of the disk will be doubled. The nucleus within the disk is unresolved ( < 0.1") and has an 
apparent magnitude m(5500 �) ~ 23.6.
The central dust absorption was noted by Mollenhoff & Bender (1987) and Kormendy & Stauffer (1987), 
but the disk structure was not evident in either case. Our preliminary analysis shows that the optical depth 
perpendicular to the disk is approximately 0.3. Radio and optical spectra show that in addition to dust the 
disk contains HI, CO, and HII. Jaffe & McNamara (1993) used the VLA and JCMT telescopes to detect HI 
and CO absorption in front of the nucleus at the galaxy�s systemic velocity. Long slit William Herschel 
Telescope optical spectra obtained for us during good seeing show a LINER spectrum with unusually broad 
lines of H-alpha, [NII], and [SII]. The nuclear H rotation curve is linear, showing that the portion of the 
disk which can be resolved from the ground rotates as a solid body.
NGC 4261 is the radio galaxy 3C 270, which has been mapped at various frequencies (Birkinshaw & 
Davies 1985, Jaffe & McNamara 1993). The radio source consists of a nuclear point source, two jets, and 
two outer lobes. The 88� position angle of the jets is essentially parallel to the minor axis of the disk. The 
dynamic time scale of the disk, ~ 106 yr for a rotation speed of ~ 100 km/s, is comparable to the 
characteristic lifetime of radio sources. Similarly, processes for transport of angular momentum, and thus 
inward transport of fuel in the disk also occur on timescales relevant to the radio jets (Pringle 1981). These 
facts, combined with the alignment of the disk with the radio axis, lead us to the conclusion that the disk is 
the �fuel� supply for the central engine, which is most likely a massive black hole. The alignment of the 
large scale radio axis with the minor axis of the nuclear disk suggests that the angular momentum in the 
disk determines the direction of the pair of collimated jets which originate near the black hole. After the 
forthcoming HST repair mission we plan to map the rotation of the disk near the nucleus to obtain an 
estimate of the central mass which is free from the ambiguities of masses derived from stellar orbits.

�Holland Ford (Johns Hopkins / ST ScI), Walter Jaffe (Leiden),
Laura Ferrarese (Johns Hopkins / ST ScI),
Frank van den Bosch (Leiden)
and Robert W. O�Connell (Virginia)

WF/PC IMAGES OF SHOCKS IN THE CYGNUS LOOP
Despite extensive ground and space-based work on radiative shock fronts, direct investigation of the 
structure of post-shock cooling and recombination regions has remained the turf of model builders. This is 
because the scale length for cooling typically about 1016 cm remains unresolved from the ground, even for 
relatively nearby objects. The high spatial resolution of the HST has now been used to address this 
problem, with very interesting results. The image above, obtained by the WF/PC IDT, shows a WF/PC 
image of [SII] emission from a field on the eastern limb of the Cygnus Loop supernova remnant. Images 
were also obtained in H and [OIII] emission. While [OIII] emission is formed in relatively hot regions close 
behind the shock, [SII] emission is seen only further behind the shock where the gas has cooled to around 
104 K. Together, these data show the structure of the post-shock flow under the wide variety of physical 
conditions found throughout the field.
For example, the isolated filament in the lower portion of the field was studied in great detail by 
Raymond et al. (1988, ApJ, 324, 869). They determined that shock velocity increases from right to left 
along this filament while the column of gas swept up by the shock decreases. They also found that near the 
center of the filament the structure must be supported by nonthermal pressure. All of these effects are 
clearly seen in the WF/PC images. Near the right end of the filament the [SII] emission collapses into a 
very sharp filament which lies immediately behind the end of the [OIII] zone, as predicted by models. 
However, no such sharp structure is seen further to the left along the filament because here the compression 
is limited by magnetic and cosmic ray pressure. Moving further toward the left side of the field, the [SII] 
filament grows progressively thinner and finally vanishes as the swept up column drops to the point that 
almost none of the shocked gas has cooled enough for [SII] emission. Along the whole length of the 
filament [SII] emission trails [OIII] emission, with the separation between the leading edges of the [OIII] 
filament and the [SII] filament becoming greater as the preshock density decreases, the shock velocity 
increases, and the time taken for shocked gas to cool to [SII] temperatures becomes longer.
In addition to adding a new dimension to the comparison of shock models with observations, these data 
also shed light on the sorts of physical processes which are important in the interaction of shocks with 
interstellar material. An especially nice example of this is seen in the upper left corner of the field where a 
very small but very bright hook-shaped structure fits neatly into a V-shaped protrusion of the shock front 
seen in [OIII]. The best explanation of this feature may be as a developing �thin-sheet� instability in which 
a bump on the surface of the shock grows as post-shock gas moves laterally to �fill in� the bump, and 
thereby increases the post-shock momentum at this location. Such instabilities have been discussed for 
some time, and it is nice to finally see one developing. It is also quite interesting that in a field such as 
this, we see only one instability developing.
The new data also allow the shock front to be used as a probe of the very small scale structure of the 
ISM. In the right hand portion of the field there are a number of very small V-shaped structures with bright 
knots at their apexes. The knots are unresolved even in these images, meaning that they are no more than a 
few hundred AU in size. The end result of the shock/ISM interaction at these locations will be solar system 
sized clouds of gas which have been significantly compressed by the passage of the shock wave. While the 
densities in this region are probably far too low for anything to come of these small knots, the significance 
of this process for shock triggered star formation in denser environments is clear.

�Jeff Hester (Arizona State University) 

EVIDENCE FOR A TIDAL INTERACTION IN THE SEYFERT GALAXY 
MARKARIAN 315
The Seyfert galaxy Markarian 315 is noteworthy for its extraordinary 80 kiloparsec long jet-like feature 
visible in redshifted [OIII] 5007 and H emission (MacKenty 1986, ApJ, 308, 571). While a tidal tail had 
been considered a possible explanation of this feature, its nature was unclear. The jet-like feature is 
extremely linear with a sharp �hook� at its end, and the galaxy itself is fairly symmetric without signs of a 
nearby neighboring galaxy. As part of a HST Snapshot survey being conducted by John MacKenty (ST 
ScI), Richard Griffiths (Johns Hopkins University), and Susan Simkin (Michigan State University), this 
galaxy was observed with the Planetary Camera in the F785LP passband in June 1992. The HST image 
(see accompanying figure) shows a second galaxy nucleus with a gaussian FWHM of 0.66 arcseconds (0.5 
kpc) which is displaced about 2 arcseconds East from the Seyfert nucleus. The second nucleus detected by 
HST is ~1/10 the brightness of the Seyfert nucleus and thus, despite its 2 arcsecond separation, is not 
visible in images from Mauna Kea in             1 arcsecond seeing. The ability to discern structures close to 
the bright active nucleus is an important benefit of the HST observations. 
This observation, combined with VLA radio maps obtained by Andrew Wilson (ST ScI) and his 
collaborators which suggest a widespread burst of star formation in this galaxy and which do not detect any 
signs of a radio jet, argues strongly for a tidal origin of the jet-like feature. Markarian 315 appears to be a 
good example of a Seyfert with a tidal interaction in which gaseous material has been perturbed deep within 
the galaxy. 

�John MacKenty


THE HST OBSERVATORY
FROM THE DIRECTOR�S OFFICE
The news of Dr. Robert Williams being named as the next Director of the Space Telescope Science 
Institute arrives just as this Newsletter is going to press. I have enjoyed knowing Dr. Williams since 1975, 
when I joined the research staff at Steward Observatory, and I share the astronomy community�s admiration 
for his superb leadership of the Cerro Tololo Inter-American Observatory (CTIO). Bob brings to the ST ScI 
his great enthusiasm for science, a dedication for service to the community, and an open, straightforward 
style of leadership. Speaking for myself and the ST ScI staff, we look forward to Bob�s and Elaine�s arrival 
in late Summer with great pleasure.
As we who are near the Nation�s capitol have learned to say, this will be a very challenging period for 
HST and the Institute. We are working hard to initiate the third observing cycle this Spring; we are in the 
process of distributing the Call for Proposals for the fourth cycle of HST observing the first cycle after the 
Servicing Mission; and we are completing our preparations for the Servicing Mission and the 
commissioning period which follows. And that�s the easy part! 
The hard part is accomplishing these activities while simultaneously improving the efficiency with 
which we schedule the Observatory and the service we give observers and visitors. In the former area, we are 
placing more emphasis on establishing a large pool of programs ready to execute and are developing a new 
optimization tool to fit these programs into the weekly schedule. The ever changing conditions of 
the spacecraft, new capabilities or workarounds, make these tasks difficult and never-ending. In the area of 
better user support, the Space Telescope Users Committee (STUC) has made several excellent suggestions, 
including ideas for simplifying the proposal process and requests for easier access to calibration data. Users 
should see some improvements in the next few months. For Cycle 4, we have lessened the amount of 
financial information required for submitting proposals. And, the recent opening of remote access to the 
HST archive should provide easy access to both archival data and calibration files.
As we look beyond the first Servicing Mission, we see a period of great promise and perhaps greater 
challenges. For those who have worked with HST or followed its successes and difficulties, it is clear that 
the upcoming servicing mission and those which follow are essential to the success of the overall program. 
>From the outset, HST was designed to be periodically serviced by the Space Transportation System the 
shuttle. Only on the basis of a long life and periodic upgrading to the state-of-the-astronomical-art, could 
NASA and the Nation rationalize the large investment and risk involved in the development of the Space 
Telescope. The growing manifest of the servicing mission attests to the reality that most orbiting 
observatories have a range of useful lifetimes between 2-4 years. Similarly, the ability to correct the 
telescope�s spherical aberration and the new capabilities offered by the Near-Infrared Camera and the ST 
Imaging Spectrograph for installation in 1997 support the concept of planned and adaptive improvements to 
the scientific payload. However, the servicing costs are substantial: similar to those of an ongoing major 
Explorer program producing an EUVE, XTE, or FUSE every three years. In an era of tight budgets, the 
challenge for HST is to keep on delivering the quality and quantity of scientific opportunities and 
discoveries that were promised when the program was designed and supported more than a decade ago. For 
the ST ScI and NASA, every servicing mission, every year, every day, and every observation is important. 
This is the context in which Dr. Williams has been selected for the ST ScI Directorship and has accepted 
the position. Again speaking for myself and the staff, we applaud the conviction and courage involved in 
both decisions.

�Peter Stockman

PROGRAM AND SPACECRAFT STATUS
The top priority activities of the HST Project are directed toward preparations for the servicing mission, 
while at the same time continuing science operations. The WFPC2 and COSTAR are proceeding toward 
delivery this year; details are given later in this Newsletter. At the same time the operational systems are 
being readied to operate HST following the servicing. Most changes required in the ground system are being 
incorporated into the systems now used for operation, but will remain dormant until activated following 
servicing. Testing of these changes is being accomplished using a test system at ST ScI which can 
reproduce virtually all of the features of the operational systems, but without interruption to ongoing HST 
operations. Later this year the ground system elements will be tested with the actual WFPC2 and COSTAR 
instruments, using the VEST facility at Goddard Space Flight Center.
Throughout the preparations for the servicing mission, HST has continued to perform steadily in the 
conduct of observations for General Observers and Guaranteed Time Observers. Steady attention has been 
given to ways to improve the observing efficiency of HST and to reduce the time lost as a result of failed 
observations. The improvements made in the target acquisition capabilities are described in this Newsletter 
under �Scientific Instruments�. 
A problem that developed with the high voltage of the FOC is also described in 
that section. 
Two significant developments in the operations of the HST spacecraft are described below.

Gyro Failure
Gyro #1 failed on 18 November 1992, and the failure signature was different from that of the previous 
two gyro failures. All telemetry output from the gyro ceased at the same instant, as if it had been turned off, 
or power removed from it. Several attempts were made by control center personnel to command it back on, 
but all were unsuccessful. The HST project at GSFC has established a failure review board that will try to 
determine the precise location of the failure. The consequences for the servicing activities on the first 
servicing mission, in December 1993, are also being reviewed. Installation of two replacement gyro units 
was already in the plan, and it is now possible that all three will be replaced.
At the time of this failure, the HST was operating with four gyros, in a mode where the redundant 
information is used to detect anomalies in any one of the four active gyros. These gyro reasonable tests 
made by the flight software correctly recognized the improper output from the failed gyro and automatically 
switched to a control law using only the remaining three gyros. The drift rates were re-calibrated within a 
few hours, so very few observations were affected. The pointing and slewing performance with three gyros 
is essentially indistinguishable from that with four gyros, so there has been no direct performance 
degradation as a result of operating on only three gyros. 
The problem now is that there are no more spare gyros available, three being the minimum set necessary 
to carry out science observations with HST. Should another gyro fail before the servicing mission replaces 
the failed gyros, HST will enter and remain in safemode configuration for an extended period of time. After 
the second gyro failed (in August 1991), a version of the flight software was developed that has a safemode 
control law which will work with no operating gyros. This control law was successfully tested on 26 
January 1993.
A working group has been formed, within the HST project, to evaluate the possibility of designing a 
vehicle control law which will work well enough with two gyros to support continued science 
observations. Those familiar with IUE history know that a succession of clever control law modifications 
have kept it operational as the number of working gyros has decreased to one. The first analysis of the HST 
situation indicates that we could get excellent performance while guiding in fine lock with only two gyros. 
The problem with HST will be during slews, SAA passages, and target occultations when the Fine 
Guidance Sensors (FGSs) cannot be used. As a result of the low earth orbit and its large size, the gravity 
gradient and aerodynamic torques on HST are significant and can lead to substantial drift if not measured in 
three axes, a function normally performed by 
the gyros.

Pointing Performance Improvements
Substantial progress has been made in improving the pointing performance in coarse track and in 
reducing the frequency of loss of fine-lock by the FGSs. These developments are partly a result of a 
sustained effort made at LMSC in Sunnyvale in upgrading their software simulation of the pointing control 
system to include actual flight performance data rather than pre-launch design data. In particular, the 
simulator now has accurate models of the point spread function as seen by the FGSs and a good model of 
the disturbances excited by the solar arrays during the day/night terminator crossings. The output of the 
simulator is now much more consistent with the flight data and has made it a better tool for assessing the 
impact of changes to the system.
The improvement in coarse track jitter performance will be roughly a factor of two, and is due to a 
modification of the control law gains. This change was made early in January 1993; data on the 
improvement will be available for the next Newsletter. 
The reduction of loss of locks in fine lock is a result of a detailed study with the simulator which shed 
much light on the actual detailed process by which lock is lost during the terminator crossings. This has 
allowed development of modifications to the flight software which will reset the FGSs to the proper place 
to regain lock, in most cases. The loss of lock rate has been about 20-30% over the last six months, but is 
expected to drop substantially after this new software is installed, also at the beginning of January. Initial 
indications are that the loss of lock rate has been reduced to 1-3%. There is a wide range in excitations from 
the solar arrays and the largest of these will probably still cause fine lock to be lost. Assuming that this is 
successful, we will once again pursue methods for allowing fine-lock guidance on fainter guide stars. 
Previous attempts at this had dramatically and unacceptably increased the incidence of loss of lock, but this 
software change should help in those cases as well. The ability to use fainter guide stars would increase the 
availability of guide stars and ease scheduling problems that are sometimes encountered in regions of the 
sky where the guide star population is sparse.

�Rodger Doxsey and Robert Milkey

COSTAR UPDATE
COSTAR has moved from design and fabrication to assembly and alignment. Essentially all of the work 
in the mechanical shop has been completed. Approximately 5000 parts were machine processed and 
assembled for COSTAR and ancillary alignment and test fixtures. The COSTAR Team at Ball began 
critical optical-mechanical alignment activities just after the beginning of the year.
During assembly and testing of the mechanisms carried by the deployable optical bench, Ball engineers 
found workmanship and reliability problems with the small motors which deploy the COSTAR mirror 
support arms. As a precaution against problems with these critical motors, we had bought backup motors 
from another vendor. Because of the problems with the original motors, we made a decision in December 
1992 to increase the margins for reliable deployment of the arms by using the backup motors. Although the 
required processing and retesting of the motors and mechanisms resulted in a loss of three weeks from our 
extremely tight schedule, we think the increased reliability justifies the delay. Ball is making every effort to 
accelerate the work to compensate for the lost time.
For optical alignment, COSTAR will be latched into a mechanical fixture (the HOMS) which simulates 
the HST focal plane and Hub structure. After alignment, COSTAR will be tested by illuminating the optics 
with beams which have the same spherical aberration as the HST. The Refractive Aberrated Simulator 
(RAS), which simulates the HST, has been completed and aligned, and will be mounted on the HOMS by 
the end of January. The RAS/HOMS will then be tested and certified by the Independent Verification Team 
from Goddard. 
Early in February 1993, the European Space Agency (ESA) will send a team to Ball to set up an 
engineering model of the Faint Object Camera (the FOC/STM) in the RAS/HOMS. The images obtained 
from the FOC/STM will be used to confirm that the RAS produces images like those seen on orbit. Later 
in the year the ESA team will return to Ball for tests which will image corrected beams from COSTAR 
through the FOC/STM f/48 and f/96 optical paths onto CCD cameras. The images will be used to verify 
that the COSTAR optics correct the HST spherical aberration 
and that the COSTAR optics are in the correct position, i.e., to verify that the light from COSTAR will go 
into the FOC. The corrected images produced by COSTAR for the FOC, FOS, and GHRS will also be 
analyzed by taking direct CCD images at the appropriate focal positions in the HOMS, and by using an 
interferometer to measure the wavefront errors in the corrected images.
Optical alignment of COSTAR will continue into March, and system integration should be completed in 
April. Extensive performance and environmental testing will occur throughout April and May in preparation 
for shipment to Goddard. After arriving at Goddard, COSTAR will be fit-checked in the protective enclosure 
which will carry it into orbit in the Space Shuttle. Next, COSTAR (and WFPC2) will be installed into a 
high fidelity, mechanical replica of the aft portion of the HST. This installation will verify critical fits and 
show that there are sufficient clearances between COSTAR, the HST and the WFPC2. COSTAR will then 
be tested with an electrical replica of the HST to verify that the electrical interface works properly and that 
COSTAR responds correctly to the commands which will be used for deployment of the optical bench and 
alignment of 
the optics.
The next 12 months will be very challenging. The teams at ST ScI, Goddard and Ball are working long 
hours to complete this critical instrument for delivery to Goddard in mid May and launch in early December 
1993.

�Jim Crocker, George Hartig
and Holland Ford

HST OBSERVES ITS FASTEST MOVING TARGET
On 10 December 1992 the HST obtained four PC images of asteroid 4179 Toutatis during its close 
approach to the Earth. At the time of the observation Toutatis was only 4.4 million kilometers from the 
Earth, about 11.5 times the distance to the moon, and moving with a geocentric apparent motion of 0.6 
arcsec/sec. Parallax correction added as much as 0.25 arcsec/sec to the tracking rates. Toutatis's
� apparent motion was nearly ten times greater than that of any previous science target.
The observations were carried out under gyro control. The tracking performed 
flawlessly and the final images are consistent with an unresolved source (2.8 km upper limit).
New software now being tested will allow future observations of fast moving targets to begin under 
guide star control using the FGSs and switch smoothly to gyro control without interruption of science 
observations. Observers planning programs for targets with apparent motions of 0.02 arcsec/sec or greater 
should contact either Keith Noll or Alex Storrs in the Science Planning Branch for more details.

�Keith Noll

UPDATE ON OBSERVING EFFICIENCY
In the November 1991 edition of the Newsletter we presented some results on the observing efficiency 
which had been achieved during the first 13 months of HST scientific observations. The purpose of this 
article is to update that discussion by presenting the observing efficiencies achieved during the past two 
years. In Figure 1 is shown the Spacecraft Time efficiency for external, primary mode targets. This measure 
of efficiency accounts for the time devoted to exposures of primary mode (i.e., parallel mode exposures are 
excluded) external targets and the associated time required for guide star acquisition, target acquisition, and 
Science Instrument control. Time lost to spacecraft and Science Instrument safemodes is excluded and is the 
reason for the weeks of lowest efficiency in the figure. During the past four months the efficiency has 
averaged 33%, whereas during the preceding year the efficiency averaged 28%. Both values are consistent 
with our goals 27.5% for Cycle 1 and 32.5% for Cycle 2. The increased efficiency has been achieved 
through improved ground operations and more effective use of the spacecraft. For example, the preparation 
of proposals for scheduling has been made more efficient through the teamwork of members of the Science 
Planning and Scheduling Branch, Science Planning Branch, and User Support Branch, as recommended by 
the Scheduling Efficiency Task Force. These teams are called Proposal Implementation Teams. The 
improvement in proposal implementation productivity has in turn allowed more time to be devoted to the 
efficient scheduling of observations. During the past year additional observing time has been made available 
through improvements in the guide star acquisition process, especially by the routine allocation of only one 
pair of guide stars rather than two pairs as was formerly the standard. As can be seen in Figure 1, the effect 
of all the improvements has been to significantly decrease the number of low efficiency weeks during the 
past four months, as well as to increase somewhat the peak efficiency during that same interval. Through 
these improvements, and others, it is our goal to maintain the efficiency at the present level through Cycle 
2 and to then increase the efficiency to 35% during Cycle 3.
While Spacecraft Time efficiency is of relevance for gauging the effectiveness of spacecraft operations, 
the exposure time efficiency is of more direct relevance for gauging the scientific productivity of the 
Observatory. That efficiency is shown in Figure 2 for the past two years. The data plotted in the figure are 
the total Science Instrument exposure time for each month, presented as a percentage of the number of 
hours in that month. Unlike the Spacecraft Time efficiency presented in Figure 1, internal targets and 
parallel mode targets are included in the total exposure time of each month. As also seen in Figure 1, the 
observing efficiency has increased during the past few months. The increase of total exposure time during 
the past few months is relatively larger than the increase of external, primary target Spacecraft Time, which 
is due in part to the increasing amount of parallel science observations.

�Larry Petro

UPDATE ON HST�S FIRST SERVICING MISSION
The servicing mission is still on the Shuttle manifest for a December 1993 launch aboard Endeavour and 
the full crew has been selected:

Richard O. Covey, Mission Commander
Kenneth Bowersox, Pilot
Story Musgrave, Payload Commander
Tom Akers, Mission Specialist
Claude Nicollier, Mission Specialist
Kathryn C. Thornton, Mission Specialist
Jeffery A. Hoffman, Mission Specialist

The suite of activities to be accomplished on HST�s First Servicing Mission has increased since the 
article in the last Newsletter. The DF-224 Co-Processor has been added to the list of activities in the 
primary objective category. This addition was made as a result of a second failed memory unit in the 
spacecraft control flight computer in late July 1992. Another gyro package and work on both 
magnetometers have been added to the list of secondary objective activities. The gyro #1 RSU/ECU/fuse 
plug addition will address the failure of Gyro #1 experienced in mid-November 1992. The magnetometer 
work is intended to address occurrences of intermittent magnetometer #1 problems that occur when the +VI 
side of the spacecraft is allowed to get cold (i.e., at an anti-sun pointing). The servicing mission now 
includes installing a new magnetometer directly over the existing magnetometer #1 and installing a thermal 
blanket on magnetometer #2.
The payload has been prioritized to achieve the mission health and safety, optical performance and 
redundancy restoration as primary objectives with secondary objective hardware carried into orbit and 
installed if time permits. The current EVA timelines indicate that all of the primary objectives and some of 
the secondary objectives can be achieved within the planned 3 EVA (6 hour) days. It is possible that a 
completely nominal, smooth mission may provide the opportunity to complete all of the EVA activities. 
The following activities, not necessarily in priority order, are included in the current list of objectives.

Primary Objectives
WFPC2
COSTAR
SOLAR ARRAYS

RSU #2 (gyros #3, #4)
RSU #3 (gyros #5, #6)
ECU #3 (electronic control unit)
DF-224 CO-PROCESSOR

Secondary Objectives
GHRS Repair Kit
Magnetometer #1 Replacement
GYRO #1 RSU/ECU/Fuse Plug
(gyros #1, #2)
Magnetometer #2 Blanket

�Peg Stanley


SCIENTIFIC INSTRUMENTS

FAINT OBJECT CAMERA
The F/96 relay of the FOC continues to work very well and to gather exciting new astronomical data in 
a wide variety of applications. The same cannot be said, unfortunately, of the F/48 relay. As the latter was 
becoming the work horse of the FOC in the Fall of 1992 with its larger field of view and use in a number 
of astronomical surveys, the high-voltage supply tripped off due to an overload condition. Use of the F/48 
was put on hold while the situation was analyzed in detail by the FOC team at the 
ST ScI and the detector contract (see description in October 1992 Newsletter). At issue was the nature of the 
overload and the possible causes. Of particular importance was to ascertain whether the degradation was 
limited to the high-voltage turn-on or -off process or whether it depended also on the amount of time the 
detector was left on. The consensus was that in the absence of hard data either way the on-off procedure 
would be softened as much as possible by reducing the slope of the high-voltage applied vs. time curve for 
the device and to limit the number of on-off cycles to the absolute minimum. All science proposals 
requesting the F/48 relay were reviewed by the FOC team at the ST ScI for their potential for transfer to the 
F/96 side. A few were deemed to be executable only with the 
F/48 if it were brought back to full operational status.
A series of tests in November 1992 to bring the detector up to full voltage with a more delicate 
procedure carried out manually were completely successful as the instrument attained and remained at its 
nominal high-voltage for the duration of the tests (several hours spread over two weeks). Dark and 
calibration flat images indicated that the instrument had returned to the conditions existing prior to the 
overload. The latter include indications that a corona discharge may be taking place between the potting and 
the outer wall of the glass body of the intensifier tube as evidenced by regions of enhanced noise in the dark 
images. The success of these tests convinced the team to resume operation at a drastically reduced rate and 
only for those programs that either absolutely required the F/48 relay or were required to gather calibration 
data necessary to reduce observations obtained before the overload event. In the course of another turn-on 
attempt in early January 1993, the detector high-voltage tripped off again at a value just below the nominal. 
It is clear then that F/48 operation is intermittent and marginal at best. Strategies to deal with this problem 
presently under discussion include the possibility of reserving a week of continuous F/48 use for the 
calibration and science programs mentioned above to be carried out in the late Spring 1993 followed by a 
shut down of the detector until after the COSTAR refurbishment. In any case, analysis of the latest event 
continues and the results will certainly influence the future approach to be taken with respect to its 
utilization. The critical factor will be its conservation for the corrected long slit spectrographic applications 
expected with COSTAR.

�F. Paresce

WIDE FIELD PLANETARY CAMERA
Mission Milestone
On 15 November 1992 during HST orbit #13949 the 10,000th WF/PC exposure was obtained. 
Approximately 50% of these exposures have been calibration observations (e.g. earth flats, internal flats, 
biases, and PSF stars).
WF/PC Information on STEIS
As the contents of the Calibration Data Base (CDB) continues to increase, observers are reminded that 
the Science Instruments Branch (SIB) is maintaining memos in the instrument_news section of STEIS 
documenting the availability of pipeline reference files, delta flats, and PSF calibration images. Also, 
abstracts of technical reports created by the WF/PC group within the Branch are posted on STEIS and these 
reports are available from the SIB secretary (fulton@stsci.edu) or from John MacKenty 
(mackenty@stsci.edu).
Stability of the Persistent Measles Contamination
Experience with the persistent measles contamination (which has been present in the WF/PC since 3 
February 1992) has shown it to be stable over time. Efforts to remove this contamination without resorting 
to a UV flood were unsuccessful and plans for a UV flood are presently on indefinite hold due to problems 
with a magnetometer which occur whenever HST is pointed at the anti-sun (required for the 
UV flood).
The evident stability of the persistent measles features permits the delta flat calibrations (previously 
obtained weekly) to be binned together over the periods between decontaminations. Since the delta flats 
correct for changes in the flat field pattern caused by the partial removal of the UV flood which occurs with 
each decontamination, as well as partially correcting for the measles pattern, a delta flat is still required for 
each such period. The new delta flat calibrations are less impacted by cosmic rays and have higher signal to 
noise ratios. Details on the delta flats, including their CDB names, are contained in the �wfpc_delta_flats� 
memo on STEIS.

�John MacKenty

WIDE FIELD PLANETARY CAMERA-2
Due to the important role in the HST mission of the WF/PC, NASA decided to build at JPL a backup 
clone of theWFPC1, a second Wide Field and Planetary Camera (WFPC2). This version of the WF/PC was 
in the early stages of construction at JPL at the time of HST launch. A modification of the internal WF/PC 
optics is able to correct for the spherical aberration and restore most of the originally expected performance. 
WFPC1 is expected to be replaced by WFPC2 in the December 1993 servicing mission, as mentioned 
previously.
The WFPC2 is now in the final stages of assembly, scheduled for completion in time for the 
commencement of system level testing at JPL in April 1993. The period between May and November 1993 
is scheduled for comprehensive instrument tests at JPL, payload compatibility checks at GSFC, and payload 
integration at KSFC. We can predict with some confidence that the WFPC2 will meet its engineering 
performance requirements on the basis of component and sub-assembly tests to date.
With the commencement of Cycle 4 observations, the General Observer community will have access to 
WFPC2. WFPC2 is a wide-field photometric camera which covers the spectrum from 1200 to 11,000 �. 
Besides optical correction for the aberrated HST primary mirror, the WFPC2 incorporates evolutionary 
improvements in photometric imaging capabilities. The CCD sensors, signal chain electronics, filter set, 
FUV performance, internal calibrations, and operational efficiency have all been improved through new 
technologies and lessons learned from WFPC1 operations and HST experience since launch.
The Principal Investigator for WFPC2 is Dr. J. T. Trauger of JPL. The IDT is C. J. Burrows, J. Clarke, 
D. Crisp, J. Gallagher, R. E. Griffiths, J. J. Hester, J. Hoessel,          J. Holtzman, J. Mould, and J. A. 
Westphal.
Single Camera
A reduction in scope of the WFPC2 instrument was mandated in August 1991 due to budget and 
schedule constraints. The result was a reduction in the number of relay channels and CCDs. The WFPC2 
field of view is divided and distributed into four cameras by a four-faceted pyramid mirror near the HST focal 
plane. Three of these are F/12.9 Wide Field cameras (WFC), and the remaining one is an F/28.3 Planetary 
camera (PC). There are thus four sets of relay optics and CCD sensors in WFPC2, rather than the eight in 
WFPC1. The pyramid rotation mechanism has been eliminated, and all four cameras are now in locations 
occupied in WFPC1 by the wide field camera relays. These positions are denoted PC1, WF2, WF3, and 
WF4, and projection of their fields of view on the sky is illustrated in the Figure . Each shutter opening 
provides a mosaic of three F/12.9 images and one F/28.3 image.
Optical Correction
Two new mechanisms have been introduced in WFPC2 to provide small amounts of alignment 
correction as may be required in the Hubble environment. The 47 degree pickoff mirror has two-axis tilt 
capabilities provided by stepper motors and flexure linkages, to compensate for uncertainties in our 
knowledge of HST�s latch positions, i.e., instrument tilt with respect to the HST optical axis. These latch 
uncertainties would be insignificant in an unaberrated telescope, but must be compensated in a corrective 
optical system. In addition, three of the four fold mirrors, internal to the WFPC2 optical bench, have 
limited two-axis tilt motions provided by electrostrictive ceramic actuators and invar flexure mountings. 
Fold mirrors for the PC1, WF3, and WF4 cameras are articulated, while the WF2 fold mirror has a fixed 
invar mounting identical to those in WFPC1. This arrangement of mirror actuators allows compensation 
for potential pupil image misalignments in all four cameras, with the expectation that mirror adjustments 
will be infrequent following the initial on-orbit alignment.
CCDs
 The WFPC2 CCDs are thick, front-side illuminated devices with a Lumogen phosphor coating, while 
the WFPC1 CCDs are thinned, backside illuminated devices with acoronene phosphor. Based on the results 
of CCD screening tests at JPL the main differences may be summarized as follows: 

Read noise:
WFPC2 CCDs have lower read noise        (7e- rms) than WFPC1 CCDs (13e- rms) which improves their 
faint object and UV imaging capability. 

Dark noise:
Inverted phase operation yield slower dark noise for WFPC2 CCDs. Thus, it is possible to operate at higher 
temperature             (-70� C) than WFPC1, which helps in reducing the build-up of contaminants on the 
CCD windows.

Flat field:
WFPC2 CCDs have a more uniform pixel to pixel response (<2% pixel to pixel non-uniformity) which 
will improve the photometric calibration of science images.

 Pre-Flash:
Deferred charge is negligible for WFPC2 CCDs. Pre-flash exposures will therefore not be required. This 
further decreases image noise and reduces overhead time. 

Gain switch:
Two CCD gains are available with WFPC2, a 7e-/DN channel which saturates at about 30,000e- (4096 
DN) and a 15e-/DN channel which saturates at about 60,000 e- (4096DN). 

DQE:
The Loral devices are thick, frontside illuminated devices with intrinsically lower QE than thinned, backside 
illuminated wafers which have no attenuation by electrode structures. On the other hand, the improved 
phosphorescent coating leads to higher DQE below about 4800 �. The peak DQE in the optical is 40% at 
7000 � while in the UV (1100-4000 �) the DQE is 10-15%.

Image Purge:
The residual image resulting from a 1004 full-well over-exposure disappears within 15 minutes, removing 
the need for CCD image purging procedures after observations of particularly bright objects.

Quantization:
The systematic Analog to Digital converter errors present in the low order bits on WFPC1 have been 
eliminated, resulting in lower effective read noise. 

QEH:
The problem of quantum efficiency hysteresis (QEH) is generally associated with thinned, backside 
illuminated CCDs and is wavelength dependent. QEH is not present in the Loral CCDs because they are 
frontside illuminated and incorporate MPP operation. The absence of QEH also means that the devices do 
not need to be UV-flooded and so decontamination procedures can be planned without the constraint of 
maintaining the UV-flood.

UV Imaging
The contamination control issues for WFPC2 may be best understood in terms of the problems 
experienced with WFPC1. Since launch, WFPC1 has suffered from the accumulation of molecular 
contaminants on the cold(-80� C) CCD windows. This molecular accumulation results in the loss of 
ultraviolet (1150-3000 �) throughput and attenuation at wavelengths as long as 5000 �. Another feature of 
the contamination is the measles contamination patches which have become progressively more difficult to 
remove with time. In addition to the loss of a UV imaging capability, these molecular contamination layers 
scatter light and seriously impact both the long and short term calibration of the instrument. WFPC2 
requires a factor of 104-105 reduction in material deposited on the cold CCD window, compared to WFPC1, 
to meet the project�s goal of achieving 1% photometry at 1470 � over any 30 day period. This goal 
corresponds to the collection of a uniform layer of no more than       47 ng/cm2 on the CCD window in the 
same period. The changes involved are:

1. The venting and baffling of the electronics has been redesigned to isolate the optical cavity.
 2. There has been an extensive component bake-out program, and changes in cleaning materials and 
procedures.
 3. The CCDs operate at a slightly higher temperature than WFPC1, which reduces the rate of build-up of 
contaminants. 
4. Molecular absorbers (Zeolyte) are incorporated in the WFPC2.

Flat-field Reference Channel
An internal flat-field system will provide reference flat-field images over the spectral range of WFPC2. 
The system contains tungsten incandescent lamps with spectrum shaping glass filters and a deuterium lamp. 
The flat-field illumination pattern will be uniform for wavelengths beyond about 1600 �, and small 
differences between the flat-field source and the OTA will be handled in terms of correction ratio calibration 
images. Short of 1600 � the flat-field is distorted due to refractive MgF2 optics, and at these wavelengths 
the channel will primarily serve as a monitor of changes in QE. This system physically takes the place of 
the WFPC1 solar UV flood channel, which is unnecessary for WFPC2 and has been eliminated.

Spectral Elements
Revisions have been made to the set of 48 scientific filters, based on considerations of the science 
effectiveness of the WFPC1 filter set, and as defined in a number of science workshops and technical 
reviews. The filter set preserves the WFPC �UBVRI� and Wide �UBVRI� sequences, while extending the 
sequence of wide filters into the far UV. The set now includes a Stromgren sequence. Wide-band UV filters 
will provide better performance below 2000 �, working together with the reductions in UV absorbing 
molecular contamination, the capability to remove UV-absorbing accumulations on cold CCD windows 
without disrupting the CCD quantum efficiencies and flat-field calibrations, and an internal source of UV 
reference flat-field images. We expect substantial improvements in narrow-band emission line photometry. 
All narrow-band filters were specified to have the same dimensionless bandpass profile. Center wavelengths 
and profiles are accurately uniform over the filter clear apertures, and laboratory calibrations include profiles, 
blocking, and temperature shift coefficients. The narrow-band set now includes a linear variable filter which 
provides a dimensionless bandpass FWHM of 1% over the 3700-9800 � range.
 
�John Trauger, Chris Burrows,
Mark Clampin & the WFPC2 IDT

GODDARD HIGH RESOLUTION SPECTROGRAPH
Side 1 Revival
As we mentioned previously, plans for the December 1993 Servicing Mission call for the installation of 
a GHRS relay box that will allow either Side of the GHRS to communicate directly with the spacecraft. 
That means that Side 1 can attempt to be revived without risk of losing the long-wavelength capabilities of 
Side 2.
	At the moment, the installation of the GHRS relay box is planned for the end of the first Extra-
Vehicular Activity on the Servicing Mission, just after replacement of the solar arrays. If the box is 
installed and operates properly, attempts will be made to revive Side 1 in incremental steps during Orbital 
Verification. Side 1 would then be calibrated and ready for science 
observations perhaps as early as the 
second half of Cycle 4 of the HST observing program.

Personnel Changes
Ron Gilliland was recently promoted to Chief of the Science Instruments Branch. Contacts for the 
GHRS are as follows:

David Soderblom 
Senior GHRS Instrument Scientist 
410-338-4543	 	soderblom@stsci.edu

Steve Hulbert
GHRS Instrument Scientist
410-338-4911 		hulbert@stsci.edu

Lisa Walter 
Technical Assistant
410-338-5036
lisa@stsci.edu

New Instrument Handbook
A new GHRS Instrument Handbook (version 4.0) has been written to go with the Call for Proposals for 
Cycle 4. The Handbook has been completely revised and incorporates the changes to the telescope and 
instrument anticipated as a result of the installation of COSTAR. We hope to revamp GHRS user 
documentation so as to provide everything an observer needs to know in one place (the Handbook). Only 
those users with truly unusual requirements should then need additional material. We welcome your 
comments and suggestions.

Recent Calibrations
� Recent tests of GHRS sensitivity show no detectable changes and the coefficients for wavelength 
solutions remain unvarying 
as well.

� Blind offsets from the large aperture (LSA) to the small aperture (SSA) the only way now available to 
place a star in the SSA have not always resulted in perfect centering, as evidenced by reduced throughput. 
Thus the improved centering discussed in the last Newsletter is not always reliable. The implementation of 
a PEAKUP capability in the SSA will obviate the problem, and we anticipate that 
capability to be tested by the time you 
read this.

� The ability of the GHRS to automatically return to the brightest object found during an acquisition�s 
spiral search has now been tested and shown to work well. BRIGHT=RETURN should always be used for 
any acquisition of a point source unless its presence in a crowded field prevents it.

�D. Soderblom, Steven Hulbert
& Lisa Walter

FAINT OBJECT SPECTROGRAPH
All modes of observation with the Faint Object Spectrograph (FOS) are working, and observing is 
proceeding normally. The test of the on-board correction to the geomagnetically induced image drift was 
performed, and the results are summarized. Also, the FOS has suffered a number of failed on-board target 
acquisitions when 
attempting to acquire variable objects. An alternative target acquisition strategy 
is described.
Since launch, FOS has suffered from a geomagnetically induced image drift due to inadequate magnetic 
shielding of the detectors. On January 6-7 a test was performed to attempt to change the internal FOS 
magnetic field so as to exactly cancel the unshielded geomagnetic field and thus cancel the undesired image 
drift. Several errors were found in the execution of the program. Although the deflections in the (FOS) X 
and Y directions were sent up to the spacecraft, and were in phase with the earth�s magnetic field, both the 
sign and the amplitude of the deflections were incorrect. The sign and the amplitude have been corrected and 
are now incorporated into the software. In addition, a status buffer error due to a benign error in 
commanding was received. The origin of the status buffer error is well understood and is being corrected. 
The intention is to correct the image drift test and to run the test again by the end of February. If the test is 
successful, on-board image drift correction will be active by the end of March 1993.
A number of automatic on-board target acquisitions have failed for objects that are variable and for 
objects with poorly known color. Hence, any object with variability in flux of greater than 0.5 magnitudes, 
or with an unknown color, must be acquired with a peak-up sequence (ACQ/PEAK) rather than the standard 
binary search (ACQ/BINARY).

�Ann Kinney

FOS spectral flat field status summary
FOS spectral flat field observations were originally obtained during SV in October, 1990 and June, 
1991. The resultant flat field reference files for both FOS/RED and FOS/BLUE were installed in the 
PODPS pipeline in October, 1991. These results are thoroughly discussed in FOS ISR CAL/FOS-075, 
S.F. Anderson, February, 1992.
Inspection of routine FOS/RED G190H, G160L, and, to a lesser extent, G270H science and calibration 
spectra taken throughout 1991 revealed dramatic changes in the high frequency flat field granularity in the 
1800-2100 � region and a substantial decrease in instrumental sensitivity over the same wavelength range.
Proposal 3975 commenced monthly monitoring of the flat field structure for FOS/RED gratings G190H, 
G270H, and G160L in January, 1992. Observations were made only with the 4.3 x 1.4 arcsec aperture on 
standard stars G191B2B and BD+28D4211. Provision was made in CDBS and the PODPS pipeline for the 
utilization of a USE_AFTER date (date after which a reference file may be valid) for each FOS flat field 
reference file, so that a series of reference files that characterize temporal changes could be maintained. 
The initial observation of proposal 3975 (2 Jan 1992) revealed an approximate 
10-15% degradation of instrumental sensitivity in the 1800-2100 � region since the October, 1990 SV 
observations. Some high frequency granulation in the same region displayed even more substantial growth. 
The continua in these flats, like those of 
the SV flats, are characterized by approximately 2% rms deviations. At the time it was noted that the 
granularity structure could be characterized as growing at the rate of about 1% per month, however, 
it was unknown whether the growth 
was continuing. 
The subsequent six proposal 3975 observations showed no more systematic growth of the features. A 
number of additional features whose depth is approximately 2% of local continuum do appear and disappear 
from one observation to the next in these observations, but there does not seem to be any substantial 
systematic growth of either new or previously existing features. Our current analysis suggests that these 
weak changes are most likely due to the slightly different centering of the target stars in the 4.3 aperture, 
hence slightly different relative sampling of the granularity of the photocathode in each observation. As a 
result, no new flat field reference files based upon proposal 3975 observations have been delivered to 
PODPS after those corresponding to the second epoch (29 Jan 1992) of observations.
The FOS/RED monitoring has continued in Cycle 2 as proposal 4123, which will execute quarterly. 
This proposal also obtains for the first time flat exposures for the 0.25 x 2.0 arcsec slit, which is a 
commonly used aperture. Qualitative evidence had indicated that the slit flat field features were substantially 
narrower and deeper than their 4.3 aperture counterparts. The first set of proposal 4123 observations (late 
November, 1992) has confirmed this appearance. Further, the structure of the 4.3 aperture flats has changed 
substantially since the last proposal 3975 observation in June, 1992! As a result, a delivery of new 
reference files based upon the November, 1992 observations has been made. The USE_AFTER date of these 
new flat filed reference files is 15-SEP-1992.
A full re-examination of FOS/BLUE and FOS/RED flat fields for all usable spectral elements with 4.3 
and slit apertures and for all usable polarimetry setups with 4.3 and 1.0 apertures will be made in Cycle 2 
following implementation of the onboard GIMP correction.

Current PODPS-pipeline FOS flat field calibration ANOMALY
The current build of the PODPS pipeline software, Build 30.1, incorrectly determines the appropriate 
reference file for ANY calibration situation in which a choice based upon reference file USE_AFTER date is 
required.
The result of this error is that ALL FOS/RED G190H, G270H, and G160L non-
polarimetric observations obtained between 21 September 1992 and 14 February 1993 have had the wrong 
flat field reference file applied in pipeline processing. The effect is that the most out-of-date, hence least 
appropriate, flat is used. A software fix was installed in PODPS on 10 February 1993. We recommend that 
any affected observation be re-processed with the correct reference file. The newly 
delivered flats mentioned in the previous section are appropriate for ALL of the affected observations.
The names of the new reference files may be found in a file named readme_newest_flats in the fos sub-
directory of the instrument_news directory on STEIS (access via anonymous ftp to stsci.edu). Queries can 
also be made to the Analysis Hot Line at 410-338-1082 or via e-mail to analysis@stsci.edu.

�Tony Keyes

SPACE TELESCOPE IMAGING SPECTROGRAPH
The Space Telescope Imaging Spectrograph (STIS) is planned for launch on the second HST servicing 
mission, currently scheduled for 1997. STIS will extend the Observatory�s spectroscopic functions, and 
provide a major extension of capability by the use of two dimensional detectors. The scientific objectives of 
the STIS team cover a wide range of topics, from planetary science to cosmology, and will ensure an 
instrument of broad utility. STIS is being developed by the Goddard Space Flight Center (Bruce Woodgate, 
Principal Investigator), and the prime contractor for the instrument design and fabrication is the Ball 
Aerospace Systems Group.

Instrument Capability
The wavelength range covered is 1150-10000 �, in 4 bands. The detectors have 1024 x 1024 pixel 
format, sampling with 2 to 2.5 pixels per resolution element. The two UV bands , 1150-1700 � (Band 1) 
and 1650-3100 � (Band 2), use photon-counting Multi-Anode Microchannel Array (MAMA) detectors with 
solar-blind CsI and CsTe photocathodes respectively. 
The two longer wavelength bands, 3050-5550 � (Band 3) and 5500-10000 � (Band 4), both use a single 
CCD Detector.
For each band, a low resolution mode with resolving power in the range 500-1500 is provided, which 
covers the entire band in one exposure and has long slits covering        25 arcsec in the UV and 50 arcsec in 
the visible/IR. For each band, a medium resolution mode with resolving power 5000-18000 is provided, 
which covers 5-10% of the band per exposure, with the long slits.
For the two UV bands, echelle modes are also provided. The medium resolution echelle modes, with 
resolving power 23000, cover band 1 in 1 exposure and band 2 in 2 exposures. The high resolution modes, 
with resolving power 105000, cover band 1 in 3 exposures and band 2 in 6 exposures. Band 2 also has a 
very low resolution prism mode with resolving power 26-200.
Autonomous target acquisition will use camera modes, which are available in each band. These will also 
allow a high spatial resolution broad band image of the spectroscopic target to be taken. The on-board 
calibration system provides for wavelength calibration and flat fields to be taken.
The spectrograph is preceded by an 
internal 2-mirror corrector for the spherical aberration and astigmatism. Focal plane coronograph stops are 
available for spectroscopic and camera modes, with 
pupil plane apodizing stops for the visible/IR modes.

Improvement Examples
The following examples illustrate the improvement of capability compared to the first generation HST 
spectrographs:
For studies of the intergalactic medium or stellar atmospheres, the spectral coverage will be 550 � in the 
1150-1700 � band at resolving power 23000, a factor 11 broader than the GHRS. Also, lower background 
rates per pixel should provide fainter sensitivity limits.
For studies of the interstellar medium, the spectral coverage will be 180 � in the 1150-1700 � band at 
105000 resolving power, a factor 36 broader than GHRS.
For studies of the velocities near the nuclei of galaxies, with a resolution of over 5000 in the visible/IR, 
the combination of detector efficiency and simultaneous spatial coverage provides an improvement of over a 
factor 40 compared to the FOS.

Technical Status
The STIS program is ramping up into the detailed design and early fabrication phase, to be ready for an 
early 1997 launch. Three demonstration MAMA detectors, two with CsI and one with CsTe, have been 
made, between them achieving the demonstration specifications and most of the flight specifications. A 
combined demonstration system comprising an optical breadboard with a CCD camera and instrument 
computer has operated together. Several gratings from the custom masters developed for STIS have been 
obtained and are under test.

�Bruce Woodgate

FINE GUIDANCE SENSORS
Progress continues to be made in the calibration of the astrometer Fine Guidance Sensor (FGS). All the 
Cycle 1 Instrument Scientist Calibration observations have been completed and the data retrieved. This was 
a �Fifteen Points of Light Test� modeled after the generic �N Points of Light Tests� used to help collimate 
the Optical Telescope Assembly (OTA). As one consequence of the availability of this data, both 
engineering usage and scientific calibration of the FGS TRANSfer scan Mode will be improved. Because 
the interferometer response appears to vary across the FGS field-of-view, owing to aberrations in the OTA 
and inside of each FGS, an increased probability of Fine Lock and a more accurate rectification of double 
star and angular diameter observations will be possible with a finer network of calibrated places in the 
astrometer FGS field-of-view.
In further calibration news for the FGSs, all the Cycle 2 Instrument Scientist Calibration proposals have 
been completed and are in the scheduling system. Similar advances continue to be made on the residual of 
Science Verification observations for the astrometer FGS. The most important news in this regard is the 
completion of the Optical Field Angle Distortion (OFAD) calibration measurements during January 10-11, 
1993. A precise knowledge of the OFAD is the largest source of uncertainty in the astrometric reduction of 
FGS POSitional Mode data. Results of the analysis of the OFAD data are expected by April 1. Since the 
ongoing Long-Term Stability Test uses the same field (i.e., M35) as the OFAD measurements, differential 
corrections to the OFAD will be available.
Finally, the Science Verification Plate Scale test has been re-configured. The success of the European 
Space Agency astrometry satellite HIPPARCOS has provided a better calibration standard than a minor 
planet. The HIPPARCOS catalog is being searched by the Space Telescope Astrometry Team for suitable 
pairs of stars; namely those of comparable magnitude, color index, proper motion, and separation in the 10-
20 arcminute range.

�Larry Taff and Mario Lattanzi


NEWS FOR HST OBSERVERS AND PROPOSERS

CYCLES 3 AND 4 PROPOSAL REVIEWS
The review and selection of the HST Cycle 3 General Observer programs has been completed. The Solar 
System Panel met at ST ScI during November 9-11, 1992 and all other Subdiscipline Panels November 16-
18, while the cross-discipline Telescope Allocation Committee held preliminary meetings on November 16-
17 and its final sessions 19-20. The TAC recommendations were subsequently reviewed by the ST ScI 
Director, and notifications of the results were mailed to all proposers during mid-December. The three 
accompanying tables present the complete membership of the Panels and TAC, a list of all approved (High 
and Medium priority) programs, and summary statistics of the review results. The deadline for Phase II 
submissions of approved programs was February 15, 1993.
The Cycle 3 review included several procedural innovations. The former Stellar Astrophysics and Stellar 
Populations Panels were revised to Hot Stars and Cool Stars, resulting in a more even distribution of the 
numbers of submitted proposals. The full TAC met on the evening of November 16 to make 
recommendations regarding the Large/Key programs, considered earlier in the day by the appropriate Panels, 
and to recommend a preliminary subdiscipline balance to guide the subsequent Panel deliberations. In 
addition, the At-Large Members of the TAC met with the Chair the following day to discuss in detail a 
representative cross-section of proposals from all the subdisciplines. Finally, a very specific procedure 
suggested by the Chair, Dr. Richard McCray, was adopted in the final TAC meetings to determine the 
boundaries between selection priorities in the ranked lists from each Panel. Two proposals at a preliminary 
target boundary were presented by the corresponding Panel Chair and discussed, followed by a vote of all 
Members (except any with conflicts). Depending on the results of the votes, the target boundary was then 
moved upward or downward and the process repeated, with convergence to a consensus boundary being 
achieved in no more than two or three iterations in every case. In view of the success of this procedure, it 
will be retained in future reviews.
Cycle 3 also required special definitions of the selection priorities because of the planned HST 
refurbishment mission in December 1993, and the attendant possible uncertainty in the duration of the 
cycle. Accordingly, three selected priority levels were adopted High, Medium, and Supplemental each 
corresponding to approximately one-third of a normal one-year cycle. It is intended to implement High 
priority programs first, but some Mediums may also be executed early due to scheduling and other 
feasibility constraints. The Supplementals constitute an inactive pool, not proceeding to Phase II initially, 
to be activated in case of a substantial delay in the refurbishment mission (not foreseen at this time). If the 
mission proceeds on the current schedule, many Medium and even some High priority programs may not be 
executed either, due to the curtailment of the cycle.
In the October 1992 issue of the Newsletter, an additional Archival Research 
opportunity with a deadline of February 1, 1993 was announced. Approximately 
three dozen proposals were received in response. They will be reviewed and results communicated to the 
proposers as early 
as possible.
Preparations for the solicitation and review of proposals for Cycle 4, the first with the corrected 
instruments, are already in progress on an accelerated schedule, since their implementation may begin as 
early as March 1994 for a nominal refurbishment mission. Issue of the Cycle 4 Call for Proposals is 
planned for March 1993, the corresponding proposal deadline will occur in May, and the peer review 
meetings will take place in July.

�Nolan Walborn & Lisa Spurrier

THE OPENING OF THE HST ARCHIVE
The HST data archive is a large and growing resource, and archival research is an increasingly important 
part of the HST program. At the end of 1992 the data accumulated since launch occupied 922 GBytes on 
nearly 550 optical disks. The HST data archive contained 24,000 public datasets 60% of which are scientific 
(not internal calibration) data.
The current archive system, the Data Management Facility (DMF) has been augmented to serve as the 
interim user service facility until ST DADS (the Space Telescope Data Archive and Distribution Service) 
comes on line. The augmentation included improving the archive catalogue and producing better and more 
uniform data products (through reprocessing), adding capabilities for the remote user to access the catalogue, 
retrieve small amounts of data directly and request larger amounts of data for later delivery on tape (through 
STARCAT), and providing support of archival research.
Reprocessing is now complete. Approximately 26,900 datasets, comprising all data obtained from 
launch to July 1992, were reprocessed. The HST archive was formally opened for archival research on         
1 February 1993.
Astronomers who want to use the archive should telnet to the VMS workstation stdata.stsci.edu or the 
Unix workstation stdatu.stsci.edu. In either case, log in with username guest and password archive. Archive 
users should type readnews to read the archive news. Guest users will be placed in the guest directory. 
Astronomers using the general guest account will be able to peruse and extract information from the catalog 
using the STARCAT program. Simply type starcat to start the program. Details and a tutorial may be 
found in the new HST Archive Primer, available from the User Support Branch. More complete 
information may be found in the HST Archive Manual. The archive primer and manual are also maintained 
as postscript files on stdata and stdatu and can be ftp-ed to your computer. Instructions are provided in the 
archive news.
Users must register in order to retrieve data from the HST archive using the workstations. Registered 
users receive a small 
personal disk area on either the Unix 
or VMS workstation and can access a large scratch area to which public HST 
data may be retrieved. To request a 
registration form, send e-mail to archive@stsci.edu, or type register from the guest account to enter an 
editor session and complete a form electronically.
Astronomers who register will be able to use STARCAT to retrieve up to 50 MBytes of public data to 
the workstation scratch area. Archival researchers can also submit requests for larger amounts of data (up to 
500 MBytes) to be written onto 9-track or 8mm tapes and shipped to the user�s home address. The requests 
can be submitted electronically using STARCAT or on paper by completing the Request for Archival Data 
form.
The Data Systems Operations Branch (DSOB), which is responsible for the HST Archive, maintains an 
�archive hotseat� to assist off-site astronomers in their archival research. The archive hotseat can be 
contacted by sending e-mail to archive@stsci.edu or by phoning 410-338-4547 during normal working 
hours. The hotseat will respond to questions concerning the user interface (STARCAT), the archive, or 
datatapes provided by DSOB to an astronomer. The hotseat will also provide limited advice concerning basic 
search strategies and will investigate and document any problems reported by users. Please direct your initial 
communications about the archive to the hotseat.
DSOB has begun to host visits to the Institute by off-site archival researchers. To assure that the time 
spent at ST ScI is productive, DSOB needs time to properly plan your visit. Therefore, both funded and 
unfunded researchers need to obtain approval from the DSOB chief for the timing and duration of their 
visits. To arrange a visit, contact the archive hotseat. A visitor hosted by DSOB will meet with an archive 
scientist (a PhD astronomer) to discuss the visitor�s needs while at ST ScI, but most of the support will be 
provided by an archive specialist (with bachelor or masters level degrees in physics or astronomy) who will 
be available as needed throughout the visit.

�Knox Long

LISTSERVER FOR STEIS FILES
The Space Telescope Science Institute has augmented its anonymous ftp account, (called STEIS for the 
Space Telescope Electronic Information Service) with listserver capabilities. Users can subscribe to certain 
popular files, which will be mailed automatically whenever they are updated. It is also possible to request 
items from the archive of previous files. The list of available files may be expanded to include other 
frequently accessed ascii files. Please send any requests for new listserver files to usb@stsci.edu.

Currently available files are:
long_range_plan:
lists observations for the coming year

weekly_timeline:
detailed weekly schedule of observations

HST_status:
daily activity/instrument status reports

completed_observations:
list of all observations completed to date

wfpc_psf_library:
point spread functions for wfpc

wfpc_delta_flats:
flat field information for wfpc

To subscribe to a listserver file, send a message with a blank subject line to listserv@stsci.edu and the 
following text::

subscribe	file name	Your Name

Where file name is one of the above file names and Your Name represents the user�s full name. Your 
return e-mail address is copied from this message and added to the list of subscribers. To unsubscribe from a 
list, just replace subscribe with unsubscribe in the above message.
For a quick overview of commands, 
send a message with a blank subject line to the same e-mail address but with the 
word HELP as the message. Listserver 
is a UNIX utility. For further assistance contact Fred Romelfanger (fred@stsci.edu, 
phone: 410-516-8641) or Pete Reppert (reppert@stsci.edu, phone: 410-338-4551).

�Pete Reppert

HST USERS COMMITTEE REPORT FEBRUARY 1993
The committee met on February 4-5 at GSFC. This is a summary of the report submitted to ST ScI and 
NASA. Users are encouraged to contact committee members (cf. ST ScI Newsletter of October 1992) about 
issues they wish raised. 
The committee was pleased at the continued success at improving observing efficiency, and the plans for 
further improvement. We are also pleased at the successful trial of the zero gyro safemode, and the plans for 
a two-gyro operational mode. We are impressed with the jitter statistics and the good performance of both 
coarse and fine lock. We note that the archival system work has proceeded on schedule and commend the 
work in that area, particularly the manuals available for this. We are pleased with the continued work on the 
�breathing� and the plans to do a multi-orbit test to characterize this more fully. Finally, the committee was 
impressed by the state of the repair mission planning, and feels considerable confidence that there is an 
excellent probability of success.
The committee is very concerned at the probable budget cutting that lies ahead, while appreciating that 
the HST project has done well in a time of great funding 
difficulty. We have recommended that 
P. Feldman be the committee representative in the group planning on how operations funding may change 
as a result of budget cuts.
 The following are summaries of the detailed points discussed:
1. The problem arising with the time-
dependent flat field for FOS-Red was discussed.
a) We recommend that all the monitoring flats obtained in 1992 be placed in CDBS as quickly as 
possible, so that individual users can then use them as seems most appropriate to them for reducing their 
spectra. A new flat field exposure has been scheduled for this month, which is very important in view of the 
significant change between the June 92 and November 92 FOS-Red flat fields.
b) We strongly recommend that a small �Flat Field Action Group� be set up soon. This group would be 
charged with: 1) recommending an appropriate suite of one-time and recurring flatfield observations to deal 
with the FOS; 2) recommending to interested users the appropriate reduction techniques for dealing with 
FOS-Red spectra; 3) making other appropriate recommendations.
The committee hopes that such an action group would serve as a successful model for other similar 
small groups to be set up as the need arises.
2. We discussed the proprietary time rules. Requests for departure from the rules must be explicitly 
included in the proposal, and considered by the TAC. Later requests for extension might be based on a) 
needing special calibrations; b) needing processing with corrected calibrations; c) incompleteness of a large 
statistical database; d) proposal use of several instruments. Later justification solely on points c) and d) 
would need to be very strong as individual observations may have other value to the science community.
3. We suggest that continuation proposals should be allowed an extra section to give the current status 
of their continuing proposal. We think it would be fair to allow continuing proposers space to mention 
updates as a result of, for example, new calibrations becoming available, small new science that has become 
known since the last proposal, or small changes in HST or instrument performance. We also note that 
officially designated continuation proposals will frequently have to be proposed BEFORE observations from 
the previous cycle have been reduced or even obtained.
4. We would like to see a system of informing observers of HST scheduling and changes up to the time 
when it is fixed. Even in cases where the program is not �time-critical�, many observers do set up 
supporting ground-based observing, and make travel arrangements. An e-mail to observers giving such 
information would be much appreciated. It should also be stressed to proposers that time-critical 
observations are harder to schedule and should thus be labelled as such only when essential. The TAC 
should be informed that time-critical observations are in general less efficient 
to schedule.
Points 3 and 4 might be made in the instructions to proposers. It would be useful to remind deferred 
Cycle 1 and 2 observers that they need to reapply in full.
5. We would like to see a system where an observer has the same contact person (or two coordinated 
persons) at ST ScI, from proposal submission to the end of data processing (so as to deal with issues of 
calibration or other problems with the data).
6. We are in agreement that the AO for a 4th generation instrument be deferred to 1994. We appreciate 
that work should start now and that it is reasonable to have a directed AO for an Advanced Camera, based on 
a phase A type study now under way. We regret that the budget for this instrument is threatened, and urge 
that a collaboration with ESA or another partner 
be pursued.
7. We are pleased to see that the OTA shrinkage has been followed and the focus adjustments modified. 
We would like the policy to be followed of keeping the focus within 5 microns of the optimum, at all 
times, by moving focus as often as necessary. This way, users will not have to worry about the focus as an 
uncontrolled variable.
8. The WFPC2 IDT presented its thermal vac and orbital verification plan. The ground tests are designed 
to minimise the on-orbit calibrations. Many instrument characteristics will be explored in TV tests only, 
and there is a Wood�s filter that is new. We thus urge that the ground test schedule at both JPL and GSFC 
be well coordinated and have contingency built in. The user community should understand the provisional 
nature of the WFPC2 calibration for Cycle 4.
9. We commend the ST ScI for its response to the moving target working group (MTARG). The user 
community is 
pleased with the recent successes in moving target observations, and awaits the imminent implementation 
of the guide star handoff capability. We also encourage further work in the area of moving target scheduling 
procedures.
10. We support the work of the STSDAS group, and would like to see assured funding for them. In the 
event of budget problems, we stress that a group of experts in the details of HST data processing is an 
extremely valuable user resource. We hope that closer collaboration with GTO teams may also help 
improve the STSDAS package capabilities.
11. We commend the work which has increased the efficiency of parallel observations. We suggest that 
efforts be made to assure that potentially long parallels (4 or more orbits) always get scheduled as their 
scientific potential is very high and 
opportunities are few. We would also like to see the ability to read out parallels into occultation.
12. We accept the proposed GHRS side 1 policy, with one suggestion. If GHRS side 1 does become 
operational, it should be offered as an option to FOS observers (presumably using G130H/blue) who would 
benefit from this alternative, with no additional observing time. TAC would award time based on the use of 
the 
FOS only.
13. We suggest that the GTO catalogue be entered in STARCAT as a general user reference.
14. Many users would appreciate help at ST ScI after hours (i.e. after 2pm Pacific time, and evenings 
and weekends) if at all possible. We suggest that ST ScI contact people be put on the finger system for 
outsiders who may wish to know if they are available. ST ScI might post their schedules on a file readable 
by observers. Two miscellaneous points: ST ScI could be more sympathetic towards many users on UNIX-
based systems; some ST ScI software, e.g., proposal preparation, on STEIS is VMS. Finally, calibration 
reference files in synphot on STEIS are out of date.
15. We are concerned over media coverage of HST performance after the repair mission. We suggest that 
the ERO program observations be confined simply to a few fields (such as star clusters) where the change in 
PSF will be very apparent for media purposes but which do not carry a new science story. We caution 
against using targets with visual appeal and no clear improved science return. New science stories should be 
released as they happen later in the course of normal observing.
16. We suggest that calibration files be included with the data in the case of all spectroscopic data. For 
imaging data we suggest that the appropriate files be available in DMF, and that the data be delivered with a 
simple recipe for getting the calibration files, if they are wanted.
The next STUC meeting is planned for May 27-28. Topics for this meeting should include Cycle 5 
planning, FOS scattered light, HST observing efficiency plans, image restoration. User input is welcomed 
by the committee.

�John Hutchings (chair),
for the HST Users Committee.

EDUCATIONAL AND PUBLIC AFFAIRS OFFICE: KEEPING THE PUBLIC TUNED-
IN TO HST SCIENCE
An estimated 14 million Americans are attentive to the space program and prefer that it be oriented 
toward scientific research. Yet only half of this group feels that they are well informed about the research 
underway. 
Public science communication is integral to the success of the Hubble Space Telescope project. Public 
affairs activities in support of HST go beyond merely 
reassuring taxpayers that they are getting a return on their investment. HST�s discoveries are inherently 
exciting and compelling for the attentive public when translated into interesting, accurate, and 
understandable articles.
In 1992 the Educational and Public Affairs Office (EPAO) issued 28 press releases on scientific findings 
made with Hubble. These results were presented in hundreds of newspaper articles, and highlighted in 
magazine stories around the world. Video news releases prepared by EPAO were featured on all the major 
networks and used extensively by Cable Network News.
Recent newspaper headlines about Hubble are increasingly far more upbeat than in the past: Hubble�s 
Successes Mount Up, Tampa Tribune; Hubble Keeps Finding New Wonders Despite Blurred Vision, 
Boston Globe; Not all Is Flawed in Hubble Images, Christian Science Monitor. HST observations were 
noted in Time Magazine�s �Best of 1992� review. Five out of thirteen astronomy discoveries highlighted in 
Science News Magazine�s 1992 year-end summary were attributed to Hubble observations.
EPAO is ready to further assist GTOs and GOs in disseminating research results to the public. Our press 
releases go to an international mailing list of several hundred science writers and reporters. The releases are 
also electronically distributed by NASA. The NASA program Space Astronomy Update allows 
investigators to present and discuss major HST findings.
Contact EPAO if you think you have results that might be of interest to the public. Of course, not every 
observation can be a �new discovery� or �significant breakthrough�. However, HST research that touches on 
such popular topics as black holes, extrasolar planets, or cosmology is always widely accepted. Even HST 
research that might not be of broad public interest receives coverage in popular science magazines and the 
science sections of major newspapers.
If you have scientific results you want to release to the public, the first step is to mail or e-mail to us a 
summary of your research along with a draft of your paper. EPAO will draft a press release tailored to 
communicate your results in an accurate and understandable manner for general reporters. The draft is then e-
mailed back to you to review for scientific accuracy.
The date of the press release usually follows the acceptance of a scientific paper for publication or 
presentation of results at a scientific conference. We will assist your university press office in co-releasing 
the results to news media. News is also simultaneously released by NASA and ESA, assuring wide 
international coverage. In addition releases are also posted on Spacelink, an electronic bulletin board 
maintained by NASA.
Most news announcements are accompanied by HST imaging data and/or graphics and artwork. EPAO 
has worked out routines for the regular transfer of scientific imaging data to the Astronomy Visualization 
Lab (AVL). The AVL provides a number of services for image enhancement, color compositing and 
annotation. These data are then sent to the photo lab for producing high-quality photographic negatives and 
prints.
The photolab has exceptional quality control that ensures that reproduction-quality prints are available for 
newspapers and magazines. EPAO also has the capability of printing descriptive captions on the back of 
each photo along with diagrams and supporting graphics.
This is a time of unprecedented progress in astronomy. Help us share in the excitement of exploration 
and discovery with 
the public.

�Raymond Villard

POLICIES FOR PUBLICATION OF HST RESEARCH
We wish to remind all authors again that research papers based on HST data must carry the following 
footnote:

�Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope 
Science Institute, which is operated by the Association of Universities of Research in Astronomy, Inc., 
under NASA contract NAS5-26555.�

If the research was supported by a grant from ST ScI, the publication should also carry the following 
acknowledgment at the end of the text:

�Support for this work was provided by NASA through grant number from the Space Telescope Science 
Institute, which is operated by the Association of Universities, Inc., under NASA contract NAS5-26555.�

So that your work can be included in official lists of HST research, please send two preprints of any 
research paper based on HST data to:

Librarian
ST ScI
3700 San Martin Drive
Baltimore, MD 21218
USA

Finally, please reference the relevant HST observing program identification number(s) in your papers, so 
that we can cross-index scientific papers with the original observing proposals.
If you have questions regarding these instructions, please contact Sarah Stevens-Rayburn (410-338-4961; 
userid LIBRARY).

�Sarah Stevens-Rayburn


SOFTWARE AND DATA ANALYSIS NEWS

HST IMAGE RESTORATION PROJECT
During the last several months work has finally gotten underway on an 18-month project dedicated to the 
restoration of images from HST. Participating in this effort are Bob Hanisch (project leader), Rick White, 
Jinger Mo, and Nailong Wu. We expect to collaborate with several groups outside ST ScI, including Bobby 
Hunt (U. Arizona), Dave Redding (JPL), Ivo Busko (INPE, Brazil), Bob Gonsalves (Tufts), and several staff 
members at the Space Telescope - European Coordinating Facility (ST-ECF). If you are working on or 
interested in HST image restoration and wish to participate in this project, please contact us.
We have three primary objectives:          1) expand our knowledge of the HST point spread function 
(PSF) and improve our ability to model the PSF, 2) develop a toolkit of restoration algorithms for HST 
data (with particular attention to the problem of the space-variant PSF of the WFPC) and provide a 
quantitative assessment of the relative merits of each technique, and      3) document the algorithms and 
approaches used for HST image restoration for GOs and provide advice on observing strategies for 
optimizing results from restoration.
In the first area we have begun a series of quantitative tests aimed at understanding the sensitivity of 
various image restoration algorithms to the accuracy of the PSF. Effects such as spacecraft jitter, the S/N 
ratio in the PSF (for empirically measured PSFs), and uncertainties in focus are being examined. Our initial 
results indicate that with the current spacecraft pointing performance (i.e., after the new on-board pointing 
software was installed) jitter is usually a negligible effect on the PSF for observations taken in fine-lock. It 
is clear that a noiseless PSF is superior to an observed PSF, however the standard PSF modeling packages 
TIM and TinyTIM are known to provide only a poor match to observed PSFs, especially in the UV. Thus, 
one of our current projects is to improve the PSF model via a phase retrieval technique. We are also testing 
a preliminary version of a PSF modeling package from JPL that uses a more sophisticated model of the 
telescope and camera obscurations than TIM or TinyTIM. Finally, numerical simulations are being run to 
determine our sensitivity to focus errors. First results indicate that systematic errors introduced into a 
restored image are generally neglible for errors of less than 5 microns in the position of the secondary 
mirror, but are significant for focus errors of 10 microns or more. Further work is required, however, using 
better PSF models.
Further enhancements to the Lucy-Richardson algorithm have been developed by Rick White. In addition 
to being able to mask bad pixels, the algorithm is now able to suppress noise amplification in low S/N 
regions. Rick is preparing a detailed paper which describes many aspects of the Lucy-Richardson technique. 
Nailong Wu has developed a maximum entropy method (MEM) package for IRAF/STSDAS that does not 
depend on any commercial software, and is preparing a report that describes MEM and the differences 
between his implementation and the popular MEMSYS5 package from Maximum Entropy Data 
Consultants, Ltd. As was announced previously, ST ScI is now able to provide the MEMSYS5 software to 
HST observers via a redistribution license we have negotiated with MEDC. The MEMSYS5 libraries are 
accessed via a front-end program developed by Nick Weir (Caltech) which Nick has kindly granted us 
permission to distribute. Please contact us if you are interested in using this software for your HST data.
As our work progresses, we intend to keep HST users informed via this Newsletter, technical reports, 
papers, and a user�s guide to HST image restoration. We also expect to host a second workshop on image 
restoration either later this year or early in 1994.

�Bob Hanisch 

STSDAS PROJECT STATUS
A status report in the last ST ScI Newsletter suggested that we would have to decrease our level of 
support for off-site users of STSDAS. Since then, the HST Project and the Institute have agreed upon a 
�System Enhancement Plan� (SEP) to fund certain enhancements to the hardware and software infrastructure 
of the Institute. A portion of the SEP calls for enhancements to user support software, and provides for the 
continuing distribution and support of STSDAS for off-site users.
As a part of the SEP, the STSDAS Group will be taking on two new projects during the next two to 
three years. The first is to provide programming support for the image restoration project that began last 
Fall at the Institute. The algorithms that are developed (or adapted) during the course of this research that are 
most useful for the restoration of HST images and spectra will be incorporated into STSDAS, so that all 
GOs/GTOs/ARs will have access to them for their own research. The second project will be to port to 
STSDAS that software which is being written for astrometric analysis with the Guide Star Catalog (GSC) 
V1.2. Our goal will be to provide GOs with portable analysis tools for accessing the GSC and the 
compressed plate scans (if they have the CD-ROM set) from workstations at their home institutions.

STSDAS Version 1.2.2 Released
The second update to Version 1.2 of the Space Telescope Science Data Analysis Software (STSDAS 
V1.2.2) was released in January, along with V1.2.2 of the TABLES external package; this version is now 
the default for most machines at the Institute. Off-site users may obtain this update, or �patch�, via 
anonymous ftp from STEIS in the directory software/stsdas/v1.2. Users who do not have access to ftp may 
request a distribution tape and installation instructions from the STSDAS System Administrator 
(hotseat@stsci.edu). If you retrieve the software electronically please send us the electronic registration form 
(which is located in that same directory) so we may keep you up to date regarding revisions to the software 
and documentation. We anticipate releasing another update (V1.2.3) in the Spring of this year.
As the STSDAS system grows and matures, some task/package reorganization and housecleaning is 
occasionally necessary. The next opportunity for such changes is in the next major release of STSDAS 
(V1.3), which we are planning for the Summer of this year. At that time we will eliminate the code 
redundancies between the TTOOLS and TABLES packages by using the TABLES source exclusively. This 
change should be transparent to most users, but off-site IRAF managers will need to install both the 
STSDAS and TABLES external packages to use all the capabilities of our software. We also intend to place 
the STSDAS.PIPELINE package (which contains all past and present versions of the RSDP reduction code) 
into its own external package. The need for the earlier versions of the RSDP is greatly diminished now that 
the reprocessing of all HST science data is complete. Users who still wish to use this code after V1.3 is 
released will need to install PIPELINE separately. These two changes will reduce the disk space 
requirements for STSDAS V1.3 by 25-30%, without losing any functionality, yet make the code easier to 
install and maintain. 

New Features of STSDAS
 Several new or improved tasks have appeared since the last incremental release of STSDAS (V1.2.1) in 
July, 1992. New tasks that relate to adaptive filtering of images are: adaptive, hfilter, and hsubtract, which 
can all be found in the PLAYPEN package. Another new task is available to users who are running IRAF 
V2.10.2 or later: chcalpar in the TOOLS package provides a unified interface for retrieving and editing the 
calibration parameters (i.e., the processing switches and the reference file names) for all science instruments. 
Other tasks have been enhanced. The forward and inverse tasks in the FOURIER package now do transforms 
much faster, thanks to improved memory management.
The STATISTICS package, which is based upon the ASURV package from Penn State, has been 
upgraded to V1.2 of that software. The TABLES package now has the ability to operate on ASCII files 
(i.e., without first having to convert them to the binary TABLES format with tcreate.) The igi task can 
now read IRAF images of all types and dimensionality (including OIF, QPOE, and GEIS files), as well as 
table columns. Various color capabilities are available in igi, skymap, and other graphics tasks through the 
new PostScript kernel, or directly through the psikern task.
A few tasks have been contributed from the HST and other user communities. They are distributed with 
STSDAS (in the CONTRIB package) as a service to the HST community, but the responsibility for the 
code, the accuracy of the output, and advice for using this software rest with the authors. One new task for 
analyzing spectra, called specfit, was written by G. Kriss at JHU. Another, called acoadd, is based on an 
algorithm developed by L. Lucy and      R. Hook (ST-ECF) for optimally coadding images with differing 
resolution. We are interested in expanding the available science applications to STSDAS users through 
GO/GTO/AR contributed software. If you have developed an interesting application, and would be willing 
to make it available to the STSDAS community, please contact us. Packages developed within the 
IRAF/STSDAS environment are especially suitable, but limited resources may be available for IRAF ports 
and/or 
collaborative software developments in some cases.
Upcoming features that will appear in the Spring (in V1.2.3) include a task to create WFPC flat-field 
reference files from streak flat observations. The �streakflat� task was based upon the algorithm that was 
developed by J. Hester of the WFPC Instrument Definition Team. This task will be especially useful for 
those GOs who obtain WFPC images using filters for which 
calibration observations exist in the archive, but for which reference files are not available in the calibration 
database. Also in the V1.2.3 release, the lucy image restoration routine will be enhanced to mask pixels 
with extremely negative values, rather than adding a large DC offset to the whole image.
Users who would like more details about STSDAS software may wish to receive the STSDAS 
Newsletter, which is prepared two or three times per year. The Newsletter provides many useful insights 
into using some of the more complicated tasks, advice on which STSDAS tasks are most appropriate for 
particular types of analyses, and descriptions of new tasks that are being developed. Please contact Mark 
Stevens (stevens@stsci.edu) to obtain the next issue. Users who have problems with the installation or use 
of STSDAS software should send a description of their problem (and the text of the error message, if any) 
to the STSDAS HotSeat (hotseat@stsci.edu). Inquiries sent to HotSeat will be acknowledged quickly, and 
any problems will be resolved as soon as possible. 

New/Updated Documentation Available
For those who are interested in writing their own IRAF/STSDAS applications, or who wish to put an 
IRAF �front-end� on their favorite routines, we have revised and updated the SPP Reference Manual. This 
manual now includes a description of the TABLES interface.
A new manual, the IGI User�s Guide, describes this very powerful graphics utility within STSDAS. 
(This guide includes a Quick Reference Card.) The IGI manual was prepared using the hypertext utilities 
that are available in the Framemaker document preparation software. Many users find this point-and-click 
style of help to be very useful, particularly if they are novice users. Users who have the Framemaker 
package available on their computers and who wish to try out this form of the IGI manual may contact 
Mark Stevens (stevens@stsci.edu) to retrieve an electronic copy of the text.

�Dick Shaw

A LOOK AT AURA: 1992
A report on AURA�s 1992 activities is hot off the press! The report highlights the Gemini Project, 
AURA relations in Chile, and the Women in Astronomy Workshop held at the Space Telescope Science 
Institute in September. Also available is an updated brochure describing AURA. Both are free of charge.
To obtain copies, contact AURA at: 1625 Massachusetts Avenue, N.W., Suite 701, Washington, DC 
20036; phone: 202/483-2101; fax: 202/483-2106.

�Lorraine Reams


INSTITUTE NEWS
THE BALTIMORE CHARTER
The ST ScI meeting on Women in Astronomy (WIA) last September was the birthplace of the Baltimore 
Charter, a set of guidelines for improving the situation of women in astronomy. The WIA meeting 
organizers had the lofty goal of producing something like the Declaration of Independence and the Bill of 
Rights combined. The final Charter has turned out to be an inspiring and, we hope, a powerful document 
for change.
The Baltimore Charter had its origin in the collective ideas of concerned people. During the September 
WIA meeting, over 200 participants were assigned to small discussion groups and asked to address various 
issues relevant to women in astronomy. The discussion topics ranged from abstract issues like how 
scientific excellence is judged, to practical problems like maternity leave, child care, and dual-career 
families. Each group produced a written report to be used as input to the Charter.
Because of the small size of the groups, discussion was intense and ideas flowed freely. The concerns and 
opinions of each conference participant were heard, and these ideas form the heart of the Charter.
Reports from the working groups were distilled and assembled into a draft document by the integration 
team, which consisted of the meeting organizers and an outside consultant, noted authority on science 
education, Sheila Tobias. The final version of the Charter states our fundamental beliefs, explains the 
underlying philosophy, issues a set of recommendations for action, and calls upon our astronomical 
colleagues to join in an effort toward change.
The completed Baltimore Charter was circulated in February to the meeting participants, who were 
invited individually to be listed as authors. The Charter appears at the front of the Proceedings of the 
meeting on Women in Astronomy, an ST ScI publication edited by Meg Urry, Laura Danly, Lisa Walter, 
and Shireen Gonzaga.
The Proceedings are being distributed to everyone who attended the meeting, to U.S. astronomy and 
physics departments, and to the ST ScI mailing list of departmental libraries. If you are not included in this 
list, and would like to receive a copy, please send your request via e-mail to Dorothy Whitman 
(schlogel@stsci.edu).
The Baltimore Charter may not solve the problems of women in astronomy but we hope it is a big step 
in the right direction. Rather than addressing the larger problem of under-representation of minority groups 
in science, we elected to focus on women because that was our area of expertise. Many of the problems 
faced by women and minorities are similar, arising from similar climates of exclusion, while other aspects 
of the two situations differ enough that the issues might best be dealt with separately. We also focussed on 
astronomy rather than science in general, again restricting ourselves to our area of expertise and our sphere 
of influence. It is our fervent hope that the Baltimore Charter will inspire equivalent documents for other 
minority groups and for other scientific disciplines.
The Baltimore Charter is not an end in itself but an opportunity, for those who care about change and 
science education, to take action and to make a difference. Our goal is that the face of astronomy reflect the 
face of the society that both supports and learns from us. We thank our colleagues for their help in 
producing the Charter and we ask all astronomers to work together toward this goal.

�Meg Urry

ANNUAL ST ScI MAY SYMPOSIUM
The topic of the ST ScI May Symposium this year is Extragalactic Background Radiation. The 
Symposium in honor of Riccardo Giacconi will be held at the Institute on May 18-20, 1993. The purpose 
of the Symposium is to review observations of the background radiation at all wavelengths and to consider 
how these may be explained by physical processes operating at various epochs of cosmic history.
The invited speakers include Jim Peebles, Peter Jakobsen, Jill Bechtold, Anthony Tyson, Simon White, 
Gianni Zamorani, Rashid Sunyaev, Mike Hauser, Carol Lonsdale, John Peacock, Malcolm Longair, Neil 
Gehrels, John Mather, Phil Lubin, Nicola Vittorio, and Martin Rees.
Shorter contributions will be in the form of poster papers. The proceedings will be published by 
Cambridge University Press.
The deadline for registration is April 1, 1993. Inquiries and applications should be sent to Tawanta Nance 
(410-338-4512, nance@stsci.edu) or Barbara Jedrzejewski (410-338-4836, eller@stsci.edu).

�Michael Fall

GALAXIES MINIWORKSHOP
ST ScI will hold a Miniworkshop on Emission from Quasar Absorption Line Systems on July 7-9, 
1993. Topics of discussion will include both continuum and line emission from absorption-line clouds over 
a wide range of redshifts. Anyone interested in attending should contact:

James Lowenthal
410-516-5101, lowenthal@stsci.edu

David Bowen 
410-338-4889, bowen@stsci.edu

Mauro Giavalisco, 410-338-4942, giavalisco@stsci.edu.

�Michael Fall

ESA FELLOWSHIPS AT ST ScI
Astronomers of ESA member countries are reminded of the possibility of coming to do research at ST 
ScI as an ESA Fellow. Prospective fellowship candidates should aim to work with a particular member or 
members of the staff at ST ScI and, for this reason, applications must be accompanied by a supporting 
letter from ST ScI.
Details of the fellowships and applications procedures can be obtained from the EDUCATION OFFICE, 
ESA, 8-10 rue Mario Nikis, 75738 PARIS 15, FRANCE. A summary of the interests of the ESA staff 
members at ST ScI can be obtained from Dr. N. Panagia (panagia@stsci.edu or 6559::PANAGIA). Their 
interests and activities can best be assessed by reading the annual report of the Institute, the most recent of 
which is in BAAS, 24, 530, 1992.
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 send to the Chairman of the Postdoctoral Selection 
Committee (currently Michael Fall) at ST ScI.
Selected Fellows must negotiate the commencement dates of their ESA Fellowships at ST ScI with the 
Academic Affairs Division (c/o Nino Panagia) at least two months before their prospective starting dates. 

�Nino Panagia

HUBBLE FELLOWSHIP PROGRAM
The 134 applications received for the fourth round of Hubble Fellowships were considered by the Review 
Panel in late January 1993. Offers to successful candidates have been made, with replies due by mid-
February 1993. 
The selection process should be completed by early March 1993 at which time the names of this year�s 
new Hubble Fellows will be announced. 
An Announcement of Opportunity for the fifth round of Hubble Fellowships will be issued in early 
Summer 1993. The deadline for submitting applications is anticipated to be mid-November 1993. 

�Nino Panagia

REORGANIZATION IN SCIENCE PROGRAMS DIVISION
Over the last few months we have re-structured several of the organizational groups within the Science 
Programs Division. Our purpose has been to improve both our service to the astronomical community and 
our scheduling and planning of science observations with the telescope. The smaller groups that we have 
produced should make for easier management and reporting.
The Telescope & Instruments Branch has been split into two smaller groups, namely the Science 
Instruments Branch (SIB) and the Science Observatory Branch (SOB). The SIB Chief is Ron Gilliland and 
includes the instrument scientists and teams working on the WFPC1 and 2, FOC, GHRS, FOC, and HSP. 
The SOB Chief is Roberto Gilmozzi and includes the scientists who work on the OTA, FGS and 
calibration activities. The Science Planning Branch has recently been restructured into two smaller 
Branches, one Branch specifically responsible for all GO and GTO Phase II implementation and headed by 
Peggy Stanley, and a second Branch led by Melissa McGrath that will be responsible for planning the long 
range schedule, moving targets and Targets of Opportunity. Several staff members from the User Support 
Branch will transition over to these implementation areas. However, USB will remain responsible for 
helping users to prepare observing proposals with HST, maintaining the electronic bulletin board (STEIS), 
documentation and TAC support, and coordinating the visits of GOs and GTOs to ST ScI. The Branch 
Chief of USB is Abi Saha.

�Duccio Macchetto and Chris Blades

RECENT STAFF CHANGES
Raymundo Baptista joined the cataclysmic variables group as a Postdoctoral Fellow in January 1993 
after completing his Ph.D. under Joao Steiner at the University of Sao Paulo, Brazil. Raymundo�s current 
research topics include multi-wavelength eclipse mapping of accretion disks, flickering, orbital period 
variations in short-period eclipsing cataclysmic variables, magnetic nova candidates, and maximum entropy 
techniques. He will be working with Keith Horne on eclipse mapping projects including applications to 
HST data.
Luciana Bianchi has joined the Institute in October 1992 as a Research Associate in the Science 
Observatory Branch of the Science Programs Division working on FOS/WFPC data of planetary nebulae 
and on UIT images of external galaxies. She comes from the Astronomical Observatory of Torino, Italy 
were she is an Associate Professor. Most of her studies in astronomy were at the University of Padova, 
Italy. Most of her research is based on observational activity in the optical and especially in the UV (IUE 
and HST), on hot massive stars (stellar wind characteristics) and evolved objects (planetary nebulae and 
XRB). She formerly worked for the IUE project as an ESA Resident Astronomer.
Kirk Borne has taken the position of DADS Project Scientist in the Data Systems Operations Branch.
David Bowen switched from an ESA Fellowship in October 1992 to a Postdoctoral Fellowship in the 
Science Programs Division. He is continuing his studies of QSO absorption lines and is collaborating with 
Chris Blades. In particular, they are analyzing HST GHRS data on several QSOs that are shining through 
the halos of foreground galaxies. First results appeared in ApJ Letters, 403, L55 for the QSO-galaxy pair 
Mkn 205 - NGC 4319.
Daniela Calzetti arrived at the Space Telescope Science Institute from the University of Rome (Italy) 
in November 1990 as an ESA Fellow. Since November 1992 she has been a Postdoctoral Fellow at the 
Institute. She is presently collaborating with Anne Kinney on a study of a large sample of UV and optical 
spectra of quiescent, starburst and Seyfert 2 galaxies. The main projects are the construction of template 
spectra of galaxies according to the Hubble type and the activity level (thermal and non-thermal) and a 
statistical study of the physical and chemical properties of the starburst galaxies in the sample. The 
template spectra will be useful for predictions of expected colors from galaxies as a function of the redshift.
Michael Dahlem joined ST ScI in January, as a Postdoctoral Fellow in the Academic Affairs 
Division. He graduated from Bonn University in 1990 and, subsequently, occupied postdoctoral positions      
at the Max Planck Institute for Radioastronomy in Bonn and at the Hamburg Observatory. At ST ScI he is 
working on multifrequency observations, including ROSAT data, of nearby galaxies, with particular 
emphasis on starburst galaxies, in collaboration with Tim Heckman, Claus Leitherer, and Ralf Dettmar.
 Michael Eracleous started a Postdoctoral Fellowsip with the cataclysmic variables group in the 
Science Observatory Branch of the Science Programs Division in October 1992 after completing his Ph.D. 
under Jules Halpern at Columbia University. Mike�s research interests include accreting compact objects in 
binary systems, particularly their oscillatory behavior, and active galactic nuclei, particularly those with 
double-peaked emission-line profiles that offer the best evidence for accretion disks. Mike is currently 
working with Keith Horne on HST observations of the 33s oscillations in AE Aquarii. His favorite bands 
of the electromagnetic spectrum are the optical (near-UV and near-IR included) and the X-ray.
Andrea Ferrara joined the Academic Affairs Division last July as an ESA Fellow. He earned his 
Ph.D. from the University of Florence (Italy) in 1992. He is mainly working on theoretical problems 
concerning the physics of the interstellar medium, both in nearby galaxies and in those at high redshifts.
Paola Grandi, who recently received her Ph.D. from the University of Padova, joined ST ScI in 
November, as a Postdoctoral Fellow in the Science Computing & Research Support Division. She is 
working on continuum processes in active galaxies in collaboration with Meg Urry.
Knox Long has moved from his position as the DADS Project Scientist to become the Branch Chief 
for the Data Systems Operations Branch.
Piero Madau joined the User Support Branch of the Science Programs Division as an Assistant 
Astronomer on October 1, 1992 after having completed a Davis Fellowship. Piero earned his Ph.D. from 
the International School for Advanced Studies, Trieste, in September 1987, and then held a postdoctoral 
position at Caltech. His main research interests include AGNs, intergalactic medium, gamma ray bursts and 
compact objects.
Jon Arthur Morse completed his Ph.D. in 1992 at the University of North Carolina at Chapel Hill. 
He joined the Academic Affairs Division last November, where he is carrying out active research programs 
in both observational and theoretical astrophysics in collaboration with Andrew Wilson. His current 
research includes observations of radiative stellar jets, SNRs and AGNs, modelling of both emission-line 
spectra in shock-excited environments and synthetic stellar spectra, kinematics of OB associations and 
young clusters, formation and evolution of blue stragglers.
Kathy Roth joined ST ScI in October 1992, as a Postdoctoral Fellow in the Science Programs 
Division working with Chris Blades. Kathy has just successfully completed her Ph.D. studies at 
Northwestern University with Professor David Meyer. At ST ScI she will continue her observational 
research on the interstellar medium and QSO absorption lines.
Emanuel Vassiliadis received his Ph.D. in 1993 from the Australian National University, working 
with Drs. Peter Wood and Michael Dopita at the Mount Stromlo and Siding Spring Observatories. 
Emanuel�s Ph.D. research was directed towards theoretical and observational aspects of Asymptotic Giant 
Branch and Planetary Nebular evolution. He is currently employed as a Postdoctoral Research Fellow, 
continuing his research into the late stages of evolution of low to intermediate mass stars. The program 
involves obtaining narrow band images and UV spectra of a sample of PN in the Magellanic Cloud and is 
in collaboration with Ralph Bohlin and Holland Ford. 
Boqi Wang earned his Ph.D. at Harvard University, and spent two years on a postdoctoral position at 
the University of California at Berkeley before taking a joint appointment at ST ScI and JHU as a Davis 
Fellow. His main interests are theoretical astrophysics, with special emphasis on interstellar medium, 
galactic halos, galaxy evolution, and radiative decay of massive neutrinos.
Brad Whitmore has returned from his sabbatical leave and taken up a new position as Deputy 
Division Head in the Science Computing and Research Support Division . In addition, he will be the acting 
Branch Chief for the Science Software Branch while Bob Hanisch works on an image restoration project for 
the next 18 months. During the sabbatical, Brad continued his work on the morphology-radius relation in 
clusters of galaxies, and began the analysis of HST observations of merging galaxies.

IN MEMORY OF 
MARCO OLIVERI
It was with sadness that we learned of the death of Marco Oliveri, which befell this past New Year�s Eve 
after a protracted fight with cancer.
Marco came to the ST ScI in 1988 after receiving his Master�s degree in Astrophysics from The 
University of Toledo, Ohio. He was one of the first Technical Assistants assigned to the newly formed User 
Support Branch and quickly became our GHRS user support specialist. He developed close working 
relationships with the GHRS Investigation Definition Team and many General Observers. He also helped 
devise many of the generalized systems and procedures which are used to support proposal solicitation, 
program selection, and the Phase II processing. In a real and substantial sense, Marco helped us navigate 
through the technical newness and several HST program shifts during the past four years.
Marco was later promoted to the position of Coordinator for the USB Technical Assistants, and provided 
strong technical leadership for the group. He received two ST ScI service awards, one for individual 
achievements and another for his contributions as part of the Proposal Implementation Team.
At work, Marco combined his buoyant sense of humor with an often stoic perseverance. He approached 
every technical challenge with an innovative and confident attitude, and often deferred his own work to help 
his coworkers and the HST users. Marco was a good friend to all, and he personified user support in its 
finest form.
He is sorely missed. 
�Bruce Gillespie 

RECENT ST ScI PREPRINTS
The following papers have appeared recently in the ST ScI Preprint Series. Copies may be requested 
from Sharon Toolan (410-338-4898, toolan@stsci.edu) at        ST ScI. Please specify the preprint number 
when making a request.

665. �A Search for Circular Polarization in Cataclysmic Variables,� H.S. Stockman, G.D. Schmidt, G. 
Berriman, J. Liebert, R.L. Moore, D.T. Wickramasinghe

666. �Radio and Optical Observations of 0218+357: The Smallest Einstein Ring?� C.P. O�Dea, S.A. 
Baum, C. Stanghellini, A. Dey, W. van Breugel, S. Deustua, E.P. Smith

667. �Interaction of Massive Stars with the Interstellar Medium,� C. Leitherer

668. �High Energy Particle Acceleration by Explosive Electromagnetic Interaction in an Accretion Disk,� 
C.A. Haswell, T. Tajima, J.-I. Sakai

669. �Photometric and Spectroscopic Analysis of High Galactic Latitude Molecular Clouds. I. Distances 
and Extinctions of Stars Towards 25 Selected Regions,� B.E. Penprase

670. �NGC 4945: A Post-Burst Infrared Galaxy,� J. Koornneef

671. �Structure, Rotation, and the Peculiar Velocity cD Galaxy in Abell 2107,� W.R. Oegerle, J.M. Hill

672. �Identification of a Ly-alpha, Radio-Quiet Galaxy at Redshift z=3.428: A Primaeval Galaxy?� F. 
Macchetto, S. Lipari, M. Giavalisco, D.A. Turnshek, W.B. Sparks

673. �Two-Stage Starbursts in the LMC: N11 as a Once and Future 30 Doradus,� N.R. Walborn, J.W. 
Parker

674. �The Mass Function of Spiral Galaxy Halos,� K.M. Ashman, P. Salucci, M. Persic

675. �Rotation and Chromospheric Emission among F, G, and K Dwarfs of the Pleiades,� D.R. 
Soderblom, J.R. Stauffer, J.D. Hudon, B.F. Jones

676. �Lyman-Alpha Emission in Star-Forming Galaxies: Low Redshift Counterparts of Primeval 
Galaxies?� D. Calzetti, A.L. Kinney 

677. �Obscuration of Quasars by Dust in Damped Lyman-Alpha Systems,� S.M. Fall, Y.C. Pei

678. �Rotation of Young Solar-Type Stars in the Orion Nebula Region,� D.K. Duncan

679. �Far-Sidelobe Contamination of the Bell Laboratories HI Survey,� K.D. Kuntz, L. Danly

680. �The Structure of the Core of 47 Tucanae from HST Observations,� G. De Marchi, F. Paresce, F.R. 
Ferraro

681. �Stellar Kinematic Groups. I. The Ursa Major Group,� D.R. Soderblom, M. Mayor

682. �An Atlas of Ultraviolet Spectra of Star-Forming Galaxies,� A.L. Kinney, R.C. Bohlin, D. Calzetti, 
N. Panagia, R.F.G. Wyse

683. �V1 in the Core of 47 Tucanae: A Possible Optical Counterpart to X0021.8-7221,� F. Paresce, G. De 
Marchi, F.R. Ferraro

684. �High-Resolution Study of Luminous IR-Galaxies: I. The Composite Nature of the Seyfert 1 Galaxy 
IRAS 2044-6114 (NGC 6860),� S. Lipari, Z. Tsvetanov, F. Macchetto

685. �Comptonization Effects as a Test for Hot Intercloud Medium in the BLR of AGNs,� A. Ferrara, P. 
Pietrini

686. �Planetary Nebulae with Binary Nuclei,� M. Livio

687. �Dwarf Nova Outburststhe Ultraviolet Delay and the Effect of a Weakly Magnetized White Dwarf,� M. 
Livio, J.E. Pringle

688. �Rotation and Activity among Solar-Type Stars of the Ursa Major Group,� D.R. Soderblom, M. 
Mayor

689. �Peculiar Velocities and Galaxy Clustering: Do Bulk and Shell Motions Have the Same Origin?� D. 
Calzetti, M. Giavalisco

690. �Optical Spectrophotometry of Oscillations and Flickering in AE Aquarii,� W.F. Welsh, K. Horne, 
J.B. Oke

691. �Multiple Hydrogen Flashes on Accreting Low-Mass White Dwarfs; Novae and DAO Stars,� M.M. 
Shara, D. Prialnik, A. Kovetz

692. �Extreme Optical Fe II Emission in Luminous IRAS AGN,� S. Lipari, R. Terlevich, F. Macchetto

693. �The Center of Gravity and Density Profile of 47 Tuc,� D. Calzetti, G. De Marchi, F. Paresce, M. 
Shara

694. �Eclipse Mapping of Accretion Disks,� K. Horne

695. �Emission-Line Diagnostics of Extragalactic Jets,� A.S. Wilson

696. �Dark Matter in Galaxies,� K.M. Ashman

697. �What Determines the Morphological Fractions in Groups and Clusters?� B.C. Whitmore

698. �The Effect of the Group Environment on Galaxies,� B.C. Whitmore 

699. �What Determines the Morphological Fractions in Clusters of Galaxies?� B.C. Whitmore, D.M. 
Gilmore, C. Jones

700. �Main Sequence Stars with Circumstellar Solid Material: The Vega Phenomenon,� D.E. Backman, F. 
Paresce

701. �Can Galactic HI Be Radiatively Supported?� A. Ferrara

702. �The Frequency of Mergers in Compact Groups,� S.E. Zepf

703. �Spectral Evolution of Stellar Populations Using Isochrone Synthesis,� G. Bruzual A., S. Charlot

704. �New High Redshift Damped Lyman Alpha Absorption Systems and the Redshift Evolution of 
Damped Absorbers,� R.L. White, A.L. Kinney, R.H. Becker

705. �Spiral Structure of the Giant Galaxy UGC 2885: H-alpha Kinematics,� B. Canzian, R.J. Allen, 
R.P.J. Tilanus

706. �Interstellar Mg II and C IV Absorption toward Mrk 205 by NGC 4319: an Optically-Thick QSO 
Absorption System,� D.V. Bowen, J.C. Blades

707. �Dynamics of Barred Galaxies,� J.A. Sellwood, A. Wilkinson

708. �Output of Matter and Radiation by Massive Stars in Different Chemical Environments,� C. Leitherer

709. �Galactic Bars with Central Mass Concentrations: 3D Dynamics,� H. Hasan, D. Pfenniger, C. 
Norman

710. �Diffuse Ionized Gas and the Disk-Halo Connection in Spiral Galaxies,� R.-J. Dettmar

711. �An HST/Planetary Camera View of Giant HII Regions: The Wolf-Rayet Content of NGC 595 and 
NGC 604 in M33,� L. Drissen, A.F.J. Moffat, M.M. Shara

712. �The Evolution of Angular Momentum among Zero-Age-Main-Sequence Solar-Type Stars,� D.R. 
Soderblom, J.R. Stauffer, K.B. MacGregor, B.F. Jones

713. �On the Mass of Nova DQ Herculis (1934),� K. Horne, W.F. Welsh, R.A. Wade

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NEWSLETTER NOTES
 Comments on this issue of the ST ScI Newsletter should be addressed to the Editor, J. Patricia Vader 
(410-338-5008, userid VADER). Mailing-list corrections should be sent to Amy Connor (userid 
CONNOR).
Persons who assisted in the preparation of this issue include John Godfrey and Dave Paradise.
The ST ScI Newsletter is issued two to four times a year by the Space Telescope Science Institute, 
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Aeronautics and Space Administration.