HST SCIENCE HIGHLIGHTS

EARLY RELEASE OBSERVATIONS WITH THE REFURBISHED HST

The Early Release Observations, or ERO, refer to the first images that were taken of science targets by HST, following correction of the spherical aberration in the optics.  All observations obtained under the auspices of the ERO program were drawn from existing science programs, both GO and GTO, although the ERO program itself is separate from those science programs.  The goals of the program were to make observations that would demonstrate the nature of the optical correction, while maintaining the science content needed to illustrate and assess the capabilities of the new HST. For example, images of M100 not only provided a dramatic illustration of the effect of the optical correction (improved dynamic range, sensitivity to faint sources, increased resolution), but also demonstrate the capability of HST to measure Cepheid variables at Virgo Cluster distances.

The optical alignments for both the WFPC2 and FOC/COSTAR proceeded quickly, well ahead of schedule.  The ERO observations thus began shortly before the New Year.  The first ERO target observed with the WFPC2 was Orion, followed in rapid succession by quasar host galaxies, M100 and Eta Carinae, and R136a and a distant cluster early in 1994.  FOC/COSTAR imaging began at the end of the first week in January, with observations of Nova Cyg, SN1987A, NGC1068 and the globular cluster 47 Tuc.

A few of these targets await release to the public, which will occur in the next few weeks.  We review here the observations that have been released.  Color gif versions of the images are available on STEIS, while the proprietary situation for the original digital data is summarized below (some but not all of the data is public).

A primary target was M100, a picture-perfect spiral galaxy in the Virgo Cluster and one of the target galaxies of the Key Project on the Extragalactic Distance Scale  (Mould et al.).  The aim of the Key Project is to measure direct Cepheid distances to about two dozen galaxies out to distances as far as the Virgo cluster. These distances will provide an accurate calibration of several independent secondary distance indicators; the ultimate goal of the program is to measure the Hubble constant to an accuracy of 10%.

The observations comprised B, V and R WFPC2 images.  Fig. 1 shows a comparison of the nuclear region of M100 taken with WF/PC-1 to the new WFPC2 image (raw data in both cases).  The smoothing and degradation in S/N that was caused by the halo of the spherically aberrated PSF is immediately obvious.  Fig. 2 shows the nuclear view in the context of the galaxy as a whole.  For a ground based picture, the Sandage-Bedke atlas may be consulted;  it covers about twice the area of the full WFPC2 field.  The resolution is striking in that the  picture of the nucleus could be mistaken for an entire galaxy. We stress that it covers only the inner few kiloparsecs.

For a more quantitative assessment of the new HST capabilities, Fig. 3 shows a small portion of the same field as observed with WFPC2 and WF/PC-1, as well as a WF/PC-1 deconvolved and a ground-based image.  The stars indicated are approximately of the luminosity expected for brighter Cepheids, although at this stage we do not know if these particular stars are actually Cepheids.  The gain in sensitivity to faint stars is obvious. The Extragalactic Distance Scale team has already undertaken photometry of the resolved stars on the new images (Freedman et al. 1994, ApJ Let, in preparation).  Preliminary color-magnitude diagrams show the presence of blue supergiants covering a range of over four magnitudes. The photometry shows good external agreement for the two epochs of data available, with rms differences ranging from � 0.02 mag for the brightest stars to less than � 0.1 mag for stars that are four magnitudes fainter. The luminosity function of these blue stars has been measured and its slope agrees extremely well with that determined in nearby galaxies. This is the first such luminosity function determination outside of the Local Group.  In addition, the position of the Cepheid instability strip in the color-magnitude diagram already reveals several dozen Cepheid candidates, and demonstrates that measuring Cepheid distances out to the Virgo cluster is feasible with the refurbished HST.  A sequence of observations with longer exposure times will be obtained in Cycle 4. This will allow for a determination of the periods of the Cepheid candidate stars and therefore of the distance to this Virgo galaxy.

The ERO data of the nuclear region of M100 (Fig. 1) also illustrate the ability of WFPC2 to chart the still poorly known centers of nearby galaxies.  The WFPC2 images of the high surface brightness inner disk of M100 reveal three structural zones:  (1) Spiral arms dominate the outer part of the nuclear disk, and eventually become confused with the main two-arm spiral pattern of M100.  Outlined by pronounced dust lanes, the outer nuclear spiral pattern is broken only when the spiral lane splits around a luminous �island.� Star clusters, and perhaps extreme supergiants, are frequent between the dust lanes in the outer half of the nuclear zone. These concentrations of young, stellar Population I objects evidently constitute the pseudo-ring that is seen from the ground.  (2) Within the inner one-third of the nuclear disk the surface density of stellar objects declines, suggesting that the star formation rate, and thus density of young stars, declines near the nucleus. In this area the dust structures become more complex and the two-arm dust pattern is lost in a swirl of dark filaments around the nucleus.  (3) The center of the galaxy contains a bright nucleus which is partially resolved, and is possibly surrounded by a bulge.

Only galaxies nearer than about 3 Mpc can be observed from the ground with comparable spatial resolution. If M100 is ten times more distant, the number of galaxies that can be studied in such detail has now increased by a factor of order 1000.

Fig. 4 shows the WFPC2 image obtained of R136, the star cluster at the center of the giant HII region 30 Doradus in the Large Magellanic Cloud. It has an age of only 3 or 4 million years.  Its core was unresolved from the ground (and speculated by some to be a supermassive single star) until speckle observations showed that it contained at least 10 stars.  Subsequent HST observations before the servicing mission resolved of order 100 stars.  With the refurbished HST we are now able to see more than 1000 stars in the core. In this case, the gain is due more to the high contrast available from the corrected WFPC2 than to the improvement in limiting magnitude.  The fainter stars were previously lost in the PSF wings from the dominant O stars.  The individual stars are photometrically distinct and can therefore be used to determine the initial mass function in this unique, young cluster.  The HII region surrounding the central cluster has also been imaged with unprecedented clarity and contrast.  Highly ionized gas boiling from the exposed surface of the nebula can be seen. We are also able to resolve �Elephant�s trunks,� structures where a denser concentration of gas has shielded the nebula from the ionizing central cluster. These trunks point toward R136.

The Orion nebula is another target that has previously been observed extensively with HST. It offers an excellent chance to compare �before� and �after� in a complex region with a great deal of structure and detail and a relatively high light level.  ERO observations were made of the region between the Trapezium and q Ori, which overlaps the region previously observed. The same emission line filters were used and F547M was substituted for F555W as it allows much better isolation of the continuum.  Two sets of observations were made, which allowed for good cosmic ray removal (far superior to hand- and computer-cleaning of individual images).  We have produced images of emission line flux (Fig. 5), using the system and filter characteristics from the Cycle 4/Phase II submission handbook, and find excellent agreement (20%) with ground-based Orion observations. We have found additional stars with �protoplanetary� material and lots of new structure in both the nebula and the two Herbig-Haro objects (Orion HH3 and HH4) that lie within the field shown in Fig. 5. The scientific analysis of these new images is the subject of a forthcoming paper (O�Dell et al., in preparation )

The star Eta Carinae has a mass of around 150 times that of the Sun, making it one of the most massive stars known.  It is highly unstable and prone to violent outbursts, the last of which occurred in 1841, when for a while Eta Carinae became the second brightest star in the sky. With WF/PC-1 images, a great deal of new detail had been seen in the rapidly expanding shell that was ejected during the outburst.  The much clearer view with WFPC2 (Fig. 6), however, shows yet more detail and amply demonstrates the capability to study faint structure very close to luminous sources.  Quite unexpectedly, this image enabled for the first time an immediate perception of the true geometric structure of the nebula. From Fig. 6, it is clear that the emission is coming from two lobes, or bubbles, bisected by an equatorial plane.  It is also readily apparent which of the two lobes lies in the foreground and which is background, because the absorbing effects due to material in the equatorial plane are evident.  It is within the equatorial plane that we see extremely high velocity material spraying out.  This is inconsistent with previous models of this and other bi-polar systems, since, amongst other things, rapid ejection generally occurs along the poles (e.g., see Nova Cyg below). The new data thus raise as many questions as they answer.  Nevertheless, with the refurbished Hubble Space Telescope, substantial progress has already been made in understanding this extraordinary and important object, and further developments are to be expected in the future.

As illustrated in the following, the combination of the Faint Object Camera and COSTAR yields both extremely high spatial resolution (essentially the full diffraction limit of HST) and good sensitivity from the visual through the ultra-violet.

A rapidly expanding shell surrounds Nova Cygni 1992, a double star system which erupted on February 19, 1992, due to a thermonuclear explosion occurring on the surface of the white dwarf component.  The new HST image (Fig. 7, right panel) reveals an elliptical and slightly lumpy ring-like structure.  The ring is the edge of a bubble of hot gas blasted into space by the explosion. The shell is so thin that the FOC does not resolve its true thickness, even with HST�s restored vision. An HST image taken on May 31, 1993 (Fig. 7, left panel), 467 days after the explosion, provided the first glimpse of the ring and a mysterious bar-like structure (see the September 1993 Newsletter). The interpretation of that image was severely hampered by HST�s optical aberration which scattered light from the central star, contaminating the ring�s image.

A comparison of the pre- and post-COSTAR/FOC images reveals that the ring has evolved in the seven months that have elapsed between the two observations. The ring has expanded from a diameter of approximately 74 to 96 billion miles.  The bar-like structure seen in the earlier HST image has disappeared. These changes might confirm theories that the bar was produced by a dense layer of gas thrown off in the orbital plane of the double star system. The gas has subsequently grown more tenuous so that the bar has faded, while the higher density has impeded expansion in that direction.  The ring has grown noticeably more oblong since the earlier image. This suggests that the hot gas is escaping more rapidly above and below the system�s orbital plane. As the gas continues escaping, the ring should grow increasingly egg-shaped in the coming years.

In summary, HST�s improved sensitivity and resolution provide a unique opportunity to understand the details of this nova explosion, long before they can be resolved with ground-based telescopes.

�Before� and �after� images of the nuclear region of the nearby Seyfert 2 galaxy NGC1068 are shown in Fig. 8.  The images were taken with filters that isolate the light from oxygen emission lines.  The active nucleus itself, perhaps a massive black-hole, is hidden from our line of sight by opaque clouds of gas and dust.  However, the intense radiation from the nucleus escapes along other directions and shows a characteristic �conical� shape, thought to be due to the shadowing effects of the same gas and dust that obscure the nucleus.  The pre-COSTAR image (left panel) already shows much fine detail that had not been seen from the ground.  With COSTAR (right panel), an incredible wealth of new filamentary structure becomes apparent, and the detailed structure of the gaseous emission can be much more readily determined.  Quantitative analysis is underway which will provide information on the strength of the radiation that is emerging from the hidden nucleus, and which will enable us to clarify the geometry of this fascinating nuclear region.

The last picture in this roundup of a few of the earliest science observations taken after the refurbishment of HST is a UV image of a small region at the core of the globular cluster 47 Tucanae (Fig. 9). It effectively demonstrates the improvement in performance with COSTAR for very rich star fields.  The pre-COSTAR image (left panel) shows many faint stars that are just visible, but which are not bright enough to be measured reliably against the background that is made up of light from the overlapping aberration halos of other nearby stars.  With the COSTAR correction, three effects come in to play that make photometry of these faint stars much easier and scientifically more useful.  Firstly, and most obviously, the fraction of light in the stellar core is increased from about 15% to well over 70% within a 0.1" radius.  Secondly, the background is lower and much more uniform, since the aberration halos have disappeared.  Finally, the plate scale change from 0.022"/pixel to 0.014"/pixel, together with the improvement in the intrinsic width of the PSF (to essentially the diffraction limit, from about 60 mas previously), allows for the separation of stars that were previously clumped too close together to be measured individually.

A rough color-magnitude diagram obtained from a quick photometric analysis further demonstrates the improvement in HST�s performance.  Whereas the main-sequence and giant branches were previously poorly defined or below the photometric limit, the new data show a well-defined main sequence with a sharp turnoff, and a clear giant branch, along with a sparse sequence of blue stragglers beyond the main-sequence turnoff.  Moreover, a small number of stars is located in the area normally populated by white dwarfs.  More work needs to be done to confirm their identification as white dwarfs, but if it holds up this will be a very important contribution to the study of stellar populations in globular clusters.  The clarity of the new data and extremely fine resolution in the new UV image offer the prospect of obtaining very high quality photometry and studying not only the luminous stellar populations of globular clusters, but also their faint, hot stellar components.

Proprietary Rights:

It was agreed early in the process of soliciting input for the program that if targets were taken from existing science programs, then, in contrast to the previous ERO/SAT exercise after launch, the ERO data would be subject to the normal proprietary restrictions for a science program (i.e., one year after the data are obtained) and that the proprietary rights would belong to the PI of the science program. The PIs all agreed to release images of their data in the form of press releases and postings of gif files etc. on STEIS.

The scientists involved are sympathetic to the view that some of the original data should be made available for public release either immediately or with a shortened proprietary period,  allowing people to improve their familiarity with the current HST and its instrumentation and assisting in Cycle 5 proposal writing.  At present, there are publicly available two Orion images and a set of four F555W WFPC2 images of M100.  When there are additional releases, a notice to that effect will be posted on STEIS, where more details on this subject may be found.  If you require access to publicly available data, please contact archive@stsci.edu.



�W. B. Sparks, C. Burrows,

W. Freedman (OCIW),

J. Gallagher (U. Wisconsin),

J. J. Hester (Arizona State U.),

R. Jedrzejewski, C. R. O�Dell, (Rice U.) and F. Paresce.



FRINGE INTERFEROMETRY OF COMPLEX FIELDS WITH THE FGS: THE FINE STRUCTURE OF R136a.

The upper mass limit for individual stars remains an open question of great importance in astronomy. Theory is not currently capable of placing a firm upper mass limit and, therefore, the problem is an observational one. Observations of the giant HII region 30 Doradus have provided some of the best candidates for the most massive stars. Here, we report on high angular resolution observations of the bright core of the  massive star cluster R136 within 30 Doradus, R136a, which had for many years been unresolved, and whose structure and photometry are still not fully explored. 

The measurements we discuss here were performed using the TRANSfer Mode of the Fine Guidance Sensor 3 (FGS3) as part of that portion of the FGS Cycle 3 Calibration program designed to explore new unique ways of using the interferometric capabilities of this instrument.  We have detected ten sources within 1", with a resolution of approximately 0.015" per axis. Accurate astrometry 

(to ~ 0.010" or better in separation and ~ 1� in position angle) and new V-band photometry (to 0.1 mag, internal error) are provided for most of these components. 

The FGS3 measurements consist of ten, identical position angle, consecutive scans, each 2.1" long with a step size of 0.0006", through R136a. The Transfer Function (TF), refers to the fringe visibility pattern produced by the Koester�s prism based interferometers inside the FGS when the 5" x 5" instantaneous field-of-view (FOV) is scanned across an 

object.

The R136a region scanned is almost coincident with that of the high-resolution FOC 

f/288 image discussed by Weigelt et al. (1991, ApJ, 378, L22). The orientation of the detector axes as projected onto the plane of the sky is such that the +X direction is 11� from the North direction (through East).  A pointing bias of about 0.5" (subsequently removed from the acquisition procedure) is evident. However, given the large FOV, this bias did not prevent the observation from being successful although in consequence the X, but not the Y, scan fell short of reaching stars a3 and a6 (following the identification code of Weigelt et al., 1991). The scan direction makes a 45� angle to the X and Y axes (about 1.5" each in length). The PMT integration time was 0.025 sec. To increase the signal-to-noise ratio (S/N) 10 multiple scans were taken and added together for a total exposure time of 10.3 min. Each individual scan has a S/N of about 3. Co-adding the scans together increases the S/N to about 11, consistent with the expected improvement of �10.  Optimal sensitivity for detection in a complex region is obtained by using the PUPIL filter element. This is a field stop placed in the beam and eliminates most of the aberration to the wavefront by reducing by 1/3 the effective mirror diameter. Although angular resolution is formally reduced by 1/3, we observed R136a with the PUPIL. 

A careful comparison of the throughput of the FGS with the PUPIL and with the F583W (Clear) filter shows that the bandpasses are quite similar (Abramowicz-Reed 1994, HDOS, private communication). We have, therefore, adopted for use with the PUPIL the effective wavelength of 5830 �, bandpass of 2340 �, and the carefully calibrated transformation to Johnson-V for the F583W filter determined by Bucciarelli et al. (1994, PASP, in press). This calibration shows that, for hot stars, the color correction would amount to less than 0.05 mag. The effect of the very high level of background light in this field (about 15 mag/arcsec2 in V as measured by the FGS itself) is to reduce by a factor 10 the peak-to-peak amplitude of the visibility fringe (the solid curves in Figs. a and b).

Although the standard algorithms used with double stars must be modified to deal with the complexity of R136a, the basic technique remains unaltered. Simply, the measurement of separations and magnitude differences of multiple component objects is performed, as for double stars, by measuring the departures of the corresponding TFs from the template TFs  of our reference single star Upgren 69 in NGC 188. We chose the reference scans which are closest, both in time and in detector space, to the observations. Figs. a and b show the results for the X and Y scans, respectively, obtained via the correlation method, which synthesizes the best possible model from the tamplate scans and compares that to the observed scans. The solid curves represent the observed TFs and the dashed lines superimposed are the residual curves. The locations and relative amplitudes, proportional to the relative brightnesses, of the �spikes� appearing on the abscissas represent the solutions of our adjustments.  The dashed curves shown in the bottom part of Figs. a and b represent the result of applying our alternative deconvolution technique to the OBSERVED TFs. There is quite good agreement between this independent method and the other solutions. As expected, the deconvolved TFs generally overlay the locations and the relative amplitudes of the set of point source positions deduced from the synthetic TF method. At this stage, local variations must be attributed to the limitations of the present implementation of the synthetic TF method, as the deconvolved TFs contain all the information of the co-added scans. 

The unambiguous identification of components a1 and a2 from our solution is simple, since they are the closest, most luminous pair of objects in the field. The finite resolving power of the instrument, and the crowded field, make the firm identifications of the remaining sources on the sky impossible without using images of comparable resolution to help establishing the identifications. Thanks to the extensive observational campaign in this field with the FOC and the PC during the last three years we now have images that can be used for this purpose. The identifications shown in Figs. a and b combine the results of projecting the FOC f/288 image discussed in Weigelt et al. (1991) and the F368M PC image of Campbell et al. (1992, AJ, 104, 1721, plate 115)  onto the FGS X and Y axes.  Here we have limited the identifications to the �classical� eight objects of Weigelt and Baier (1985, A&A, 150, L18) and to new  components which appear as close companions of some of them. 

The Table lists separations (r), position angles (PA, J2000 equinox), and magnitude differences [�V (Johnson) per axis and average] with respect to star a1, according to the identifications given in Figs. a and b. The separations and the PAs have been derived from the projected separations reported in detector space (also in the Table) For components a3 and a6 we  have only the Y scan as mentioned earlier. The new companion of the a1-a2 system is identified as a1B in Figs. a and b. This new component is about 1.1 mag fainter than a1 and 0.08" away from it. On the Y scan, a7 is partially aligned with the a1-a2 system (as seen on the FOC and PC images). According to the X scan magnitudes, a7 is 0.4 mag fainter than a1B. This explains the less satisfactory quality of the fit near the spike identified as �a1B & a7� on the Y scan (Fig. b) when compared to the residuals near the X scan spike of a1B, but the magnitude difference is still  consistent between the two axes. The smallest projected separation resolved here is ~ 0.025" between a1B and a2 which is consistent with the 0.015" resolution limit we had previously established through Monte Carlo simulations. 

Campbell et al. list a10 and a11 as close companions of a3 and a6, respectively. FY1 is our candidate for a10, although the FGS photometry is ~ 0.7 mag brighter. The projection of the field is particularly crowded in that portion of the Y scan, and in the absence of an X scan (which would yield a much clearer signal in this case) we expect a larger error in our photometry. Therefore, FY1 is most likely Campbell et al.�s object a10. As for a11, we see a component in our Y axis solution about 0.040" away from a6, consistent with the total separation given in Campbell et al. (~ 0.070"). However, a11 is 0.5 mag brighter than a6 according to the PC photometry, and our candidate for a11 is 1.3 mag fainter than a6, which is fainter than the mag limit of interest here. Components a4 and a8 are clearly resolved with a separation of 0.13". Star a8 has the largest discrepancy between the magnitude differences derived from the two single axis solutions. The Y value is expected with a larger error as the X scan solution shows better agreement between the synthetic method and the deconvolved TF. Finally, the sharp spike at 2.029" seen on the X axis is identified as �a13 & a23�. The FOC and PC images show that it is an almost perfect chance alignment (a12 of Campbell et al. is also included) of stars of comparable magnitude. In Campbell et al. a13 and a23 are about the same F555W magnitude, and a12 is ~ 0.5 mag fainter. In the case of perfect alignment, we can predict from  the F555W PC data that the three stars together would appear only 0.2 mag fainter than a1. The value from the X axis solution for �a13 & a23� is 0.36 mag, giving us added confidence in our technique. 

We have adopted the values of Vo-M(V)=18.6, A(V)=1.2, and V(a)=10.77 for the (intrinsic) distance modulus to the LMC, the extinction, and the integrated magnitude of R136a, respectively. The relative magnitudes in the Table, although  generally consistent with previous work, do show significant differences. Thus, they provide new material with which to estimate the mass of R136a1. These numbers imply M(V)a=-9 for R136a. From the  photometry in the Table we derive V(a1)-V(a)=1.75, implying MV(a1) = -7.25. Campbell et al. (1992) have established that component a1 is a WR star, and ground based spectroscopic work classifies the R136a complex as type WN6. A lower limit for the luminosity of a1 is set by adopting the bolometric correction for type WN6, B.C.=-3.6. We obtain Mbol(a1)=-10.85 and Log(L/Lo. = 6.24 (log Te = 4.59). 

Using Maeder�s models (1990, A&AS, 84, 139) for a LMC metallicity  of 25% that of the Sun we calculate a present day mass as low as 30 Mo., main sequence progenitor mass of 60 Mo., and age around 4 Myr. These values are the lowest for the direct mass determination of a1. Finally, the potential exists that a1 could reveal itself as a multiple star below the FGS limit of 1000 AU at the distance of the LMC. 

We have reported on the results of the first high angular resolution observations taken with FGS3 aboard the HST of a star cluster embedded in very bright background. The strong and complex background around the R136 cluster in the 30 Dor nebula does not prevent FGS3 from achieving its angular resolution limit of approximately 0.015" per axis and V photometry to 0.1 mag. We provide evidence for a third component, a1B, within the a1-a2 system with a separation of 0.08", or a distance of approximately 4000 AU from a1. Finally, estimates from current evolutionary models of massive stars based on the new FGS photometry predict that the present mass of the brightest object in R136a, R136a1, is 30 Mo., with a main sequence progenitor of 60 Mo. (Lattanzi, Hershey, Burg et al. 1994, ApJ Lett, in press). 

Such results clearly demonstrate that the TRANS mode of operation of FGS3 is indeed viable in dense fields with high levels of diffuse background. The S/N degradation imposed by reduced fringe visibility has limited effect on the best angular resolution achievable and can be somewhat recovered with multiple scans. 



�R. Burg (JHU), M. G. Lattanzi,

J. L. Hershey, L. G. Taff, S. T. Holfeltz and B. Bucciarelli



Resolving the Young Planetary Nebula He 3-1357

 Prior to our HST observations, the optical nature of He 3-1357 had to be inferred from spectroscopic and photometric data of the nebula as a whole.  He 3-1357 was suspected of being a proto- or young planetary nebula (PN) because, over a number of years, similarities have been noted between B[e] stars and protoplanetary nebulae, and also because the far-infrared IRAS flux distributions and colors for He 3-1357 are similar to those of young PNs.  Previous studies of He 3-1357 have measured only physical parameters averaged throughout the nebular volume due to the lack of spatial resolution.  Its small size precluded the ground-based acquisition of optical maps, although early observations identified He 3-1357 as an early-type emission-line star.  UBV photometry had implied that the central star is gradually becoming hotter.  Analyses of infrared data showed that, for a star, He 3-1357 has an infrared excess and that its infrared (IRAS) colors were typical of a young PN.  

The exact nature of the various phases of mass loss that PN progenitors undergo is still unclear, so we observed a number of nascent PNs with HST, including He 3-1357.  Four snapshot exposures of He 3-1357 were made in August 1992, using the Planetary Camera with narrow band filters.  Two exposures were made with the Hb filter (F487N) and two with the [O III] 5007 � filter (F502N).                              

Observations of He 3-1357 over the past four decades have revealed significant changes in its spectrum.  Circa 1950, Karl Henize saw only the Ha line in emission, while recent observations show strong forbidden lines consistent with a young PN. Our HST images in both Hb and [O III] 5007 � (see Fig.) show a compact nebula surrounding the central star.  The image shown in this figure was created by deconvolving the average of two exposures. Projected on the plane of the sky, the nebular gas appears most strongly concentrated in an ellipse with its major axis subtending 1.6" from NW to SE.  If this ellipse is actually a circular ring viewed obliquely, then our line of sight is inclined from the symmetry axis by 56�.  Above and below the ring of gas appear to be two bubbles containing lower-density gas.  The axial symmetry defines a polar axis (whose projection is the apparent long axis of the nebula) and an equatorial plane (perpendicular to the polar axis and passing through the center).  The full extent of the nebula from pole to pole is 2.3" in the NE-SW direction.  While the holes in the ends of the bubbles are visible in both Hb and [O III], the escaping gas is more easily seen in the [O III] images.  The �blowout features,� where the gas inside of the bubbles has broken through at the poles, are also seen in numerical models of Wolf-Rayet (WR) bubbles.  Models of WR bubbles using a three-wind model, taking into account different winds from the Main Sequence and Red Supergiant (RSG) stages of the central star, show that Rayleigh-Taylor instabilities form in the polar regions causing the gas to fragment into clumps.  The RSG wind then can flow freely out between the clumps.  At this stage, most of the hydrogen emission comes from the fragmented shell of swept-up RSG wind and [O III] emission comes from shocked gas bursting through the shell.  

The Hb flux, corrected for reddening, is 5.8 x 10-11 erg cm-2 s-1 which is a factor of 3.0 higher than the Hb flux in 1990.  The [O III] 5007 � flux, based on our HST observations and corrected for reddening, is 

6.4 x 10-10 erg cm-2 s-1.  This is higher than the 1990 flux by a factor of 3.5 and is considerably different from several decades ago when no forbidden line emission was evident at all. 

At a distance of 5.6 kpc, the approximate radius of this nebula is 0.022 pc.  Based on the width of the [O III] 5007 � line, an expansion velocity of ~ 8 km s-1 has been estimated for the ionized shell.  This yields an �expansion age� of 2650 yr.  From the Hb flux, the ionized mass is estimated to be 0.2 Mo..

From the small size of He 3-1357, this PN might be expected to be optically thick.  If this is the case, the stellar luminosity can be estimated from the Hb flux.  We find log L*/Lo. = 3.7 which, in turn, implies a core mass of 0.59 Mo..  A higher core mass would be more compatible with the fast evolution that is observed in He 3-1357, but mass loss has probably influenced the evolutionary time scale.

If a PN is known to possess at least axial symmetry, it is in principle straightforward to infer the three-dimensional (3-D) structure from the observed 2-D projection.  In practice this is easier said than done because small noise fluctuations get amplified by the process.  Since the intensity in any direction is an integral of the emission along the line of sight, small fluctuations tend to get averaged out in the 2-D projection.  The actual 3-D structure must always be clumpier than the 

2-D projection appears. In addition to the intensification of noise, numerically deprojecting the 3-D emissivity from a 2-D image can result in regions with negative emissivity.  Various averaging processes have been used to overcome these problems.  In the case of He 3-1357, such a deprojection procedure would also be problematic because there are two axes of symmetry �one defined by the torus and one defined by the polar holes in the bubbles of gas above and below the torus.  These two axes differ (in projection) by 11�.  In view of these complications, an alternative approach is to construct a parametric model based on the geometrical appearance of the nebula.  Such a model implies that the nebular gas in He 3-1357 is contained in only 40% of the volume of a filled ellipsoid having the same outer dimensions.  In fact, the obvious inhomogeneities show that most of the gas is in a still smaller volume.

The axisymmetric structure of He 3-1357 may be the result of the interaction of a binary companion with the primary�s envelope during common envelope evolution.  Many PNs with close binary nuclei have bipolar shapes and, in the case of He 3-1357, the moderate density contrast between the equatorial and polar regions may indicate that the progenitor had evolved to a late AGB stage before encountering the common envelope phase.  Alternative explanations for the equatorial-to-polar density contrast have included rapid stellar rotation or remnant material from a protostellar disk.  However, a mechanism for simple bipolar mass ejection is not sufficient in view of the polar holes being off-axis.  If the observed structure is the result of some combination of effects of stellar rotation and common envelope evolution, the 11� difference between the axes defined by the equatorial ring and the polar holes may be the result of the progenitor star�s axis of rotation being tilted with respect to the orbital plane of the binary.  A similar morphology, with much of the circumstellar material concentrated in a torus, is seen in the SN1987A nebula and even in the Crab Nebula.  In fact, it has been suggested that the SN1987A system is actually an hourglass-shaped bipolar nebula.  While the origin of this morphology is not yet fully understood, it is clear that it is a widespread phenomenon. 



�Matt Bobrowsky

(CTA INCORPORATED)



HST Observations of Comet Shoemaker-Levy 9 and Its Impact with Jupiter

Plans for HST observations of comet Shoemaker-Levy 9 and Jupiter are well underway.  A specially convened TAC met in December and chose six teams, some including investigators from more than one proposal, to conduct observations of the comet and its impact with Jupiter this coming July.  A science team meeting was held at ST ScI in January where the PIs collectively decided on an efficient orbit-by-orbit observing strategy during the particularly intense impact week (July 16-22).  The approximately 100 orbits of time allocated to the campaign is spread over many months, some of the first comet observations have already been released to the press (see figure), and the final observations will be made just before Jupiter enters the 50� solar avoidance zone in late August.  A science team report is expected by late November.

Slightly more than 1/3 of the orbits are allocated to comet imaging and spectroscopy.  The remaining 2/3 is divided between several programs aimed at visible and UV imaging of Jupiter and its aurorae, spectroscopy of Jupiter, and a search for emissions from the magnetosphere.  The approved programs are listed in the table.

On behalf of the entire community, we would like to extend our grateful appreciation to Dr. Robert Millis (Lowell Obs.) who served as TAC chair, and to the panel members, Drs. R. Brown (ST ScI), C. deBergh (Obs. de Paris, Meudon), M. Flasar (NASA-GSFC), R. Gladstone (SWRI), D. Hunten (U. Arizona),  and K. Meech (U. Hawaii).



�Keith Noll and Ethan Schreier





THE HST OBSERVATORY

DIRECTOR�S PERSPECTIVE

The successful refurbishment of the HST has been well publicized during the past few months, and the satisfaction of seeing excellent data come out of the telescope is immeasurable.  Credit for this accomplishment goes to so many people that one cannot begin here to properly assign it.  The outcome are new capabilities of high spatial resolution and UV and optical spectroscopy that we hope will be of great significance for all of astronomy.  While the HST users enjoy the improved performance of the telescope, the Institute must already begin planning for the 1997 Servicing Mission which will see the installation of the Near Infrared Camera (NICMOS) and the Space Telescope Imaging Spectrograph as well as the refurbishment of several crucial observatory support systems. 

The recommissioning of the HST observatory, the new Wide Field Planetary Camera 2 (WFPC2), and the COSTAR-corrected science instruments  has gone very smoothly and ahead of schedule, so Cycle 4 scientific programs are already well underway.  Award letters announcing the GO awards were sent in March, as well as letters for all Cycles 1-3 programs that will be carried over into Cycle 4.  As we have received the responses from the PI�s concerning the revised observing programs for these carryover programs, we have begun scheduling the observations.  Within the usual scheduling constraints, we give some priority to the completion of the high priority Cycles 1-3 programs over the execution of new Cycle 4 programs.  However, since the carryover observations represent only an additional 5 weeks  of HST usage, Cycle 4 observers should not notice any significant delay in the implementation of their programs.  

With the HST�s performance now restored to its original goals, we have placed the highest priority on improving service to HST observers.  As discussed in the article concerning the PRESTO initiative, we are simplifying the Phase I submission of proposals for Cycle 5 and unifying the various tasks involved in scheduling the telescope in order to make this process more efficient and responsive to the users and the ever changing conditions of the HST.  In the future, HST users should find the initial proposal process more friendly and the follow-on technical definition of their programs more straightforward.  We are also pursuing new initiatives in other areas of user-services, namely data quality and scientific advice.  Since the success of these efforts will rely on correctly addressing the desires and recommendations of HST and archive users, we will utilize the ST Users Committee (STUC) and directed surveys of the user community to help us in this crucial area.

Service to HST users is our most important task, but the ST ScI must also prepare for the exciting scientific opportunities offered by the new science instruments, STIS and NICMOS.  With their installation less than 3 years in the future (February 1997), a great deal of responsibility falls to the Institute to assist in integrating these instruments into the HST observatory, support a very broad spectrum of new science capabilities, and properly present the opportunities that these new instruments offer to the astronomy community.  At the same time, we must look beyond the 1997 mission to the servicing mission planned for late 1999, a shuttle visit which will provide a critical reboost to the HST in order to ride out the next period of high solar activity.  We are very pleased that NASA has provided funding for the development of an Advanced Camera for installation in 1999.  We expect that many scientists, including some within the ST ScI, will be working to respond to the Announcement of Opportunity (AO) which NASA released in March.  The AO includes many of the recommendations of the committee on the Future of Space Imaging (FOSI) and makes a compelling case that a state-of-the-art camera for HST in the 1999 timeframe will open up new windows of scientific investigation. 

With all this good news, we do not find the FY95 budget situation for the HST Project very encouraging.  The reductions in the HST Project, which are discussed in the article by the STUC Chair, reflect the difficult situation that all science funding is experiencing throughout the country and, in particular, across-the-board reductions in the NASA Astrophysics funding of ongoing mission operations and data analysis (MO&DA).  Within these reduced guidelines, NASA is doing its best to ensure the 15-yr lifetime for the HST mission.  However, as the STUC article summarizes, the budget reductions over the previously approved levels creates a number of risks to the long-term health of the HST program.  With actual operations (ST ScI and GSFC) being reduced by approximately 20%, it will be difficult to squeeze in preparations for the 1997 and 1999 missions.  On the servicing side, both NICMOS and STIS are being developed under more austere conditions than the original HST instruments and the development of these instruments and  additional flight hardware, such as batteries, spare high gain antennae, etc.,  have become the contingency for any future budgetary and development problems.  In this, the HST program is no exception.  Other major NASA missions (AXAF, FUSE) and important programs waiting for new starts (SOFIA and SIRTF) have also been rescoped to fit a slowly declining budget for space science.  We hope that the new discoveries made by the new capabilities in space (e.g., HST) and on the ground (e.g., the VLBA and the giant 8m and 10m telescopes) will engage the American public in the exciting vistas of exploration and knowledge offered by modern astronomy.  We intend to work with the astronomy community in getting these discoveries and the fascination of astronomy into the home and the classroom.



�Bob Williams and Peter Stockman



SERVICING MISSION OBSERVATORY VERIFICATION (SMOV)

As reported in the last issue of this Newsletter, SMOV consists of a coordinated set of activities designed to recommission the HST spacecraft and its complement of science instruments (SIs) for normal science operations following the successful Servicing Mission.  The several dozen tests were scheduled to be carried out over a 15 week period following the mission.

We are happy to report that at the time of this writing SMOV is proceeding well ahead of schedule in most areas and virtually all of its original goals have been met.  The spacecraft is operating efficiently with three of the four SIs already performing high-quality Cycle 4 astronomy.

The new Wide Field and Planetary Camera (WFPC2), after initial activation and engineering check-out, proceeded rapidly to an initial alignment that not only served to demonstrate the basic success of its corrective optics but also allowed accelerated scheduling of the Early Release Observations (EROs) which were undertaken during the last week of 1993 and the first few days of the new year.  The resulting images became instant media hits when unveiled at the famous NASA Press Conference on the morning of January 13, 1994.

Currently, WFPC2 is interleaving a large set of SMOV and Cycle 4 calibrations with Cycle 4 science observations.  It is performing very well.  As of this writing, a set of Secondary Mirror focus sweeps has just been successfully performed and, after analysis of the WFPC2 data, resulted in the final fine positioning of the WFPC2 mirrors as well as the OTA secondary.

The Corrective Optics Space Telescope Axial Replacement (COSTAR) is fully deployed, aligned, and focused with the SIs it serves.  Its major SMOV milestones include Deployable Optical Bench deployment (along with FOS M2 Mirror Arm) on December 26.  First Light using COSTAR optics was achieved by the Faint Object Camera (FOC) on December 28 and its success in correcting HST�s spherical aberration was immediately apparent in the very first image.

The FOC was the first of the SIs to complete its alignment with COSTAR (January 7), at which time it proceeded immediately to its scheduled set of Early Release Observations which, under severe time constraints, were processed in time for the January 13 NASA Press Conference as well as the following day�s AAS presentation.  On January 23, the FOC became the first SI to complete its SMOV program.  Since that time it has been used exclusively for f/96 Cycle 4 science.

The Goddard High Resolution Spectrograph (GHRS) COSTAR mirror arm was deployed on January 21 and GHRS first light through COSTAR occurred on the next day. GHRS alignment with COSTAR was completed on February 14.

Side 2 of the GHRS has been fully aligned and focused with COSTAR, SMOV calibrations are complete, and Cycle 4 science has begun.  Side 1 of the GHRS, which could not be safely used until redundancy of its science data path was restored by the Servicing Mission, has undergone its SMOV reactivation and high-voltage check-out.  Resumption of Side 1 science is pending more Cycle 4 calibrations scheduled over the next several weeks.

Only the Faint Object Spectrograph (FOS) awaits further SMOV testing needed to determine the precise V2-V3 location of its small apertures in order to perform the astronomy specified in Cycle 4 proposals.  These tests are scheduled to be completed by the end of March.  The FOS first light through COSTAR occurred on January 1.  Its alignment with COSTAR proved relatively difficult, but was achieved on February 23.

A great deal of credit goes to a large number of talented people throughout the HST Project who, working long hours over the holiday season, have made SMOV a success.



�Carl Biagetti



Optical Telescope Assembly (OTA)

Collimation:  On December 23, 1993 the OTA was collimated to remove residual coma by moving the secondary mirror by -19.4, 92.1 �m along the V2, V3 axes, respectively.  FOC f/96 images at 632 nm taken before the move showed coma of ~ 1/19 th waves, while after the move the coma was ~ 1/60 th waves. This latter value is within the uncertainty of the measurement.  Hence, we conclude that coma has been removed and the OTA is now collimated.

Focus:  OTA focus monitoring through December 1993 showed that the OTA desorption is now less than a micron per month.  During SMOV, three OTA secondary mirror moves were made by the WFPC2 team for focusing purposes.  The secondary mirror is now 19 �m farther from the primary mirror than before the moves.  The focus position may be slightly adjusted after the WFPC2 fine alignment test at the end of February.

Optical Modelling Software (TIM and Tiny  Tim):  The software package TIM (see October 1992 ST ScI Newsletter) developed at ST ScI to model Point Spread Functions (PSFs) for the HST science instruments has been updated (release 30) and is available on STEIS.  Release 30 replaces release 27, the major changes between the two being an updated desorption curve to estimate focus values, better alignment positions for WFPC obscurations, an option to generate WFPC2 PSFs with user defined aberrations, and a new subsidiary program for computing encircled/ensquared energies.  Additional features have been added to some subsidiary programs. COSTAR corrected instruments may be modelled using the option provided for a user defined instrument.  Default aberrations have not been provided for the refurbished science instruments. User manuals may be obtained from the User Support Branch, ST ScI.  For questions contact hasan@stsci.edu  Another program, Tiny Tim, written independently by John Krist (see March 1992 ST ScI Newsletter) to generate PSFs for the HST cameras, is also available on STEIS. 



�Hashima Hasan



SCIENTIFIC 

INSTRUMENTS

Fine Guidance Sensors

The recent activities of the Institute�s Fine Guidance Sensor group have been concentrated on supporting the SMOV phase, writing up several calibration reports (Instrument Science Reports 26, 27, and 28 are distributed, #29 is almost finished), and evaluating the effects on FGS science resulting from the movement of the secondary mirror of the Optical Telescope Assembly to the �zero coma� position during SMOV.  The milli-arc second level performance of the FGS in a crowded, high-background field (the 30 Doradus region of the Magellanic Clouds) has been demonstrated.

There were almost no high priority guidance or FGS-related problems during SMOV. Therefore, we were able to devote a considerable amount of time and energy finalizing Instrument Science Reports on many of our pre-SMOV calibration activities. Report #26 presents the definitive results of the photometric calibration of the astrometer FGS using the POSition Mode measurements acquired for the Optical Field Angle Calibration (OFAD); a fuller document is in press in the PASP (April 1994). Report #27 summarizes the TRANSfer Mode calibrations utilizing the �N Points of Light� tests for N = 7. Report #28 presents the results of a quick-look at an all FGS engineering calibration designed to ascertain guidance parameters in the FGE. This engineering proposal gave us our first post-SMOV look at all three FGSs. Finally, Report #29 deals with the expansion of FGS observing capabilities to crowded fields with high background levels.  In addition, it presents the significant extension of the two methods of Transfer Function analysis developed at the Institute and has led to an ApJ. Lett. (1994, in press) paper.  This work demonstrates unmatched resolution in the core of cluster R136a and the validity of the analysis methods used to interpret the data.  As time permits we will incorporate the new algorithm into the Institute�s astrometry pipeline.



�Larry Taff and Mario Lattanzi



The Performance of the COSTAR Corrected Faint Object Camera

At the end of January 1994, the Faint Object Camera successfully completed all expected SMOV activities, and officially started Cycle 4 observations.  SMOV executed flawlessly and the two main objectives were achieved. First, it was established that COSTAR could indeed satisfactorily correct the spherical aberration. This was already pretty clear in the first light observation of the astrometric cluster NGC 188, taken on December 28, 1993. Although defocus and coma were still present in the stellar images, the central 0.1" radius region already contained 54% of the total light, compared to the previous 18%. In the following days, the COSTAR mirrors were adjusted in real time to optimize the focus, eliminate the coma, and generally produce the final best image quality, which exceeded the specifications by achieving 85% encircled energy in 0.1" radius at 4860 �. A comparison can be seen in Fig. 1 between the pre- and post-COSTAR FOC Point Spread Functions, in terms of radially averaged profiles (Fig. 1a) and encircled energy (Fig. 1b). The table lists the characterizing parameters (fraction of the total light in the central pixel and encircled energy in 0.1" radius) of the FOC corrected PSF, as a function of wavelength. It is interesting to note how the central pixel (14 mas) now contains 6 - 9% of the entire flux, while the encircled energy varies from 85% at 4860 � to approximately 58% at 1400 �. This is due to scattering in the UV which slightly increases the PSF wings.

The new plate scale was determined from images of a field in 47 Tuc, taken and compared to Cycle 2 and Cycle 3 images of the same field.  The plate scale derived from the full format zoomed images is 0.01435 "/pixel, in good agreement with the preliminary numbers obtained by the NGC 188 observations.  With these new values, the FWHM for the PSF at 4860 � becomes about 42 mas, while at 1400 � it is slightly larger (about 52 mas).

The second objective of SMOV was to give a coarse assessment of the performance of the FOC + COSTAR system, starting with the f/96 aperture location. With a modified plate scale of 14 mas/pixel, all the imaging formats are reduced in size, making the acquisition of targets more difficult. The largest format (512x1024 zoomed) now available for the FOC f/96 (f/151 in reality, we will continue calling it f/96 for practical reasons) is 14" x 14", with a limited 8 bit dynamic range, while the standard 512" x 512" becomes now 7" x 7" (see Instrument Handbook, version 4.0). Images of astrometric standards in NGC 188 were taken on January 10, 1994, after the final tip/tilt adjustments were executed. The positions of the stars measured in these images resulted in a determination of the center of the new f/96 aperture that was only about 2.4" from the value that was being used throughout SMOV and agreed well with the earlier determinations, made prior to final COSTAR adjustments. The Project Data Base was updated with the new numbers and observations taken January 26 verified that this position produced accurate pointing. However, it has become necessary to be even more careful in providing accurate target coordinates, and to account correctly for proper motion, because an error as small as 2" can now result in a failed observation with the standard 512 format, if we fold in the usual Guide Stars uncertainties. We strongly recommend the use of Interactive Acquisition for all formats smaller than 512" x 512".

Finally, we assessed the sensitivity of the FOC + COSTAR system (Fig. 2). The observations were performed on January 14, 1994. We imaged a UV spectrophotometric standard, BPM 16274, which had been extensively observed before refurbishment. We selected seven medium band and one narrow band filters, in order to ensure optimum coverage in the wavelength interval 1200 � - 5500 �. The ratio between the measured post-COSTAR and pre-COSTAR fluxes at each wavelength was then compared to the expected model (dashed line in Fig. 2), which was based on the reflectivities of the COSTAR M1 + M2 mirrors. The observed 

f/96 sensitivity matches the expected values very well. The total throughput, therefore, is now 0.080 counts/photon at 3200 � and 0.019 counts/photon at 1500 �, as compared to 0.105 counts/photon at 3200 � and 0.028 counts/photon at 1500 � prior to the installment of COSTAR. We do not observe any absorption feature or loss in throughput due to contamination. For the purpose of observation-planning, the values reported in the handbook can be used, with a 5% decrease correction factor accounting for the mirror coating aging which was not included in the handbook calculations.



�Antonella Nota and Robert Jedrzejewski



Goddard High Resolution Spectrograph

Among many other things during the Servicing Mission, the astronauts installed the GHRS Repair Kit (RK) and tested its operation.  The RK allows either side of the GHRS to communicate independently with the spacecraft data bus, and doing so allows 

Side 1 to be revived with virtually no risk to Side 2.  The success of the RK has been demonstrated often since the SM because all data now come through Side 2 transparently.

The first test for GHRS in SMOV was an acquisition of a calibration star to verify that no detectable movement of the instrument�s apertures occurred, followed by a measurement of sensitivity.  This measurement showed that count rates were higher than before the SM by about 9%.  This increase is caused by a change in the focus position of the secondary mirror of HST, and was expected.  The GHRS was the last instrument to have its COSTAR mirrors deployed, and while it was waiting it was possible to obtain observations for eleven Cycle 3 GO programs.  GOs who obtained data during this period or those who access archival data should be aware that fluxes will appear to be too high by 9%, but that this is a spurious increase.

The deployment and alignment of the COSTAR mirrors for the GHRS has gone smoothly and on schedule.  The main effect of COSTAR for the GHRS is to roughly double the throughput of the Small Science Aperture (SSA) relative to its pre-COSTAR value, due to the improved Point Spread Function (PSF) that COSTAR provides (see Fig. 1).

We have tested the post-COSTAR sensitivity of the GHRS and find a higher degree of wavelength dependence than was anticipated.  In other words, we expected that light loss due to the two reflections of the COSTAR mirrors would just about compensate for the light in the wings of the PSF that COSTAR now brings into the Large Science Aperture (LSA).  The fraction of the pre-COSTAR PSF that made it through the LSA was essentially independent of wavelength, and so we expected the ratio of post-COSTAR to pre-COSTAR sensitivity to be near unity.  Instead this ratio is about 1.15 near 1300 � but drops to 0.80 at 2000 �, rising again to 1.00 at 2500 � and exceeding 1.0 beyond that.  The reasons for the shape of this sensitivity curve are not known at this time, but the departures from unity are modest and should not affect Cycle 4 science programs.  A series of observations will be obtained to monitor sensitivity.  The ratio of post- to pre-COSTAR sensitivity is shown in Fig. 2.



Side 1 Revival

As mentioned, the RK installation enables the revival of detector 1 of the GHRS and its modes of operation with gratings G140L, G140M, and Echelle-A.  A deliberate and careful reactivation plan has been followed (written and executed with the help of H. Garner and D. Ebbets of Ball Aerospace).  At this time the full high voltage has been applied to the detector and basic tests have been run, all without incident and all nominally successful.  The next steps are to obtain an observation of the spectral calibration lamp and to observe calibration stars.  An Early Release Observation is planned for Side 1 as well and is likely to have been completed by the time you 

read this.



�David Soderblom



Faint Object Spectrograph

 Cycle 3 absolute photometric calibration and aperture ratio calibration measures were obtained in September 1993.  The point source aperture throughput analysis for all calibrated apertures, including some paired apertures for the first time, has been completed.  See CAL/FOS-106 and its update CAL/FOS-120 (both by Bohlin) for details.

As part of the ongoing effort to develop a set of standard stars with accurate spectrophotometry between 1050 and 10,000 �, Bohlin (see CAL/SCS-002) has compared the FOS flux spectrum for G191B2B with a pure hydrogen atmosphere model spectrum in order to derive the difference between the current HST flux scale and the scale defined by the physics of model atmosphere calculations.  Bohlin and Lindler are currently working on a new flux calibration algorithm that will include known changes in FOS instrumental photometric sensitivity as a function of date of observation, secondary mirror position, and aperture for all detector/disperser combinations.  This algorithm would apply to all data obtained since launch.

FOS/BLUE flat field observations for the 4.3 aperture and, for the first time, the slit aperture were obtained at the end of November 1993.  FOS/RED 4.3 aperture flats were successfully obtained in late October as part of the FOS/RED superflat program for G191B2B.  All of this material will be analyzed to produce complete superflat-based flat fields.  A general announcement will be made to the user community when these flats are available.

FOS operations have proceeded smoothly in SMOV.  To date we have executed observations to verify the immediate post-servicing, but pre-COSTAR, baseline sensitivity, to measure post-COSTAR-deployment location of spectra, and to establish the coarse and fine alignment of the FOS large apertures.

As this Newsletter goes to press, internal wavelength, flat field, and absolute photometric calibration observations have recently executed.  The FOS plate-scale, aperture size, and precise small aperture location observations are also scheduled for execution during March 1994.

Modest modifications of FOS Y-bases were made in early January 1994 as a result of the location of spectra measures.  All changes were consistent with well-established trends from the Cycle 2 and Cycle 3 time period.  No obvious changes attributable to the Servicing Mission were detected.  See CAL/FOS-116 (Koratkar et al.) for details.

The pre-COSTAR-deployment baseline sensitivity observations were compared with essentially identical data from Cycle 3.  No changes, other than those clearly consistent with a small secondary mirror position adjustment, were detected.  See CAL/FOS-118 (Keyes et al.) for details.  By the publication date of this Newsletter we anticipate incorporation in the PODPS pipeline of flux calibrations for the 4.3 and 1.0 apertures with all usable detector/disperser combinations derived from post-COSTAR observation. Most other apertures will be corrected with aperture throughputs based on models of the post-COSTAR PSF. Prior to this time, output post-COSTAR FOS flux files were identical to the output count-rate files (i.e., a unity sensitivity correction was applied). The output flux files for the 0.1-pair apertures and both barred apertures will continue to be identical to count-rate files.

Coarse and fine alignment measures completed by March 1 have proceeded successfully.  As a result, some Cycle 4 GO/GTO programs have already begun execution.  Proposals that utilize ACQ/BIN and obtain science with either the 4.3 or 1.0 aperture and those that utilize ACQ/PEAK and perform science with the 4.3 aperture are being included on current observing calendars.  The first such observation occurred on Feb-

ruary 9.

Although formal requirements for the completion of SMOV for FOS will be met by the successful execution of the wavelength, flat field, and photometric programs, GO proposals that use single apertures smaller than 1.0 or use paired apertures for science will commence scheduling only after successful completion of the precise small aperture fine alignment.



�Charles D. (Tony) Keyes



References:

Bohlin, R.C., CAL/FOS-106, October 1993.

Bohlin, R.C., CAL/SCS-002, December 1993.

Bohlin, R.C., CAL/FOS-120, February 1994.



Keyes, C., Kinney, A., Koratkar, A., and Taylor, C., CAL/FOS-118, January 1994.



Koratkar, A., Taylor, C., Kinney, A., and Keyes, C., CAL/FOS-116, January 1994.





NEWS FOR HST OBSERVERS AND PROPOSERS

Schedule for Cycle 5

SMOV went very smoothly and allowed us to recommence science observations in February.  This being the case, we anticipate completing Cycle 4 high- and medium-priority proposals by the early summer of 1995.  (We anticipate activating Cycle 4 supplemental proposals only if we suffer a major instrument problem or a comparable event that prejudices the existing science program.)  Hence, we are already planning for Cycle 5!  We anticipate that the Call for Proposals will be made in June, with a deadline of mid-August for Phase I proposals.  The HST TAC will meet in early November and the Phase II programs will be required by January - February 1995.  We are planning new submission forms as well as new procedures for this round, as described below.



� Chris Blades



Project to Re-Engineer Space Telescope Observing (PRESTO)

Beginning in November 1993, ST ScI embarked on a major effort to improve the way we plan and schedule HST and the way we support HST users throughout this process. It is a continuation and significant expansion of our successful initiative to increase observing efficiency. The new project is named PRESTO, which stands for Project to Re-Engineer Space Telescope Observing. This project will be one of the most important activities of the Institute in the coming year. Its fundamental goal is to improve the proposal implementation process and provide better service to the astronomical community. The specific objectives for Cycle 5 include:



� simplify proposal generation (Phases I and II), submission and implementation;



� increase user visibility into the planning and scheduling process;



� increase flexibility and responsiveness of the overall system; and



� further increase HST system throughput and efficiency.



In the long run we expect to reduce the lead time between proposal submission and execution.

PRESTO incorporates the current User Support, Observation Preparation, and Science Planning Branches from the Science Programs Division, the Science Planning and Scheduling Branch from the Operations Division, and the Advance Planning Systems Branch from the Science and Engineering Systems Division. In order to provide the necessary organizational flexibility, PRESTO is run out of the ST ScI Director�s Office as a special project under the oversight of Ethan Schreier and the management of Mark Johnston.

PRESTO is currently working on simplifying the Phase I and Phase II proposal forms, eliminating redundant information, and simplifying the submission process. For Phase I, we expect that no special software will be required for proposal preparation, and that a straightforward LaTEX proposal template will be the basic mechanism. We are contemplating fully electronic submission, possibly on an experimental basis for Cycle 5, and would be interested in hearing from anyone who would like to try this out. In addition, four key aspects of a new operations concept have been defined.

First, beginning with Cycle 5, observing time will be allocated and observations will be defined by visits. A �visit� is an ordered series of exposures on a target. Intuitively, a visit encompasses all the activities from the start of guide star acquisition on a target until the telescope is ready to slew away to the next target. In today�s system, visits are not defined directly by the observer, but are inferred based on the exposure logsheet. Because of the REPEAT and DEF SEQ/USE SEQ syntax in Phase II proposals, a single logsheet line can ultimately appear in many visits, and a change to a single special requirement can dramatically alter the structure of a proposal. This has been a continuing source of confusion and has made it hard to accommodate proposal changes.

Second, we will allocate time by orbits. The allocation and accounting of HST observing time has traditionally been by Spacecraft Time (ScT) which includes exposure time, instrument overheads, guide star acquisition and re-acquisition times, real-time contact and decision times, and small angle maneuvers. Orbits are by contrast the more natural unit on the spacecraft and their use, combined with the visit concept, will provide more insight for the proposer about how to design their observations. Many observers already �think� in terms of orbits (to the extent possible given the limited information about overheads) and then adjust their exposure times to try to meet their ScT allocation. However, they must submit their Phase II proposals without any orbit information at all, so it must be re-derived during the Institute�s processing of each proposal. The new process would allow the observer to optimize their own visits by specifying exposure orderings and durations to make the best possible use of allocated HST observing time. 

Third, each approved HST program will be assigned a primary contact within the institute who will have end-to-end responsibility for proposal support throughout the life of the program (from selection through execution). ST ScI considers it absolutely essential to provide high-quality support to observers on a person-to-person basis. This is a critical aspect of the proposal writing process due to the complexity of HST. And it goes far beyond simply writing the proposal to touch on every aspect of getting the proposal implemented.

Finally, in the planning and scheduling area, PRESTO is working towards a single system and a single team approach to help bridge the historical gap between the SOGS SPSS1 and the upstream proposal implementation and long-range planning systems. Two key aspects of this change are more stable long-range planning, although at coarser time resolution, and reduction of lead time for detailed scheduling.  The development of a long-range plan at coarser time resolution will make it easier to be flexible in generating the detailed observing schedule, while still providing the HST observer with better insight into when their observations will be taken. In the past, the long-range plan was generated with an assumed one-week time resolution, but we found that it was rarely possible to meet this plan, and, because of the long lead times, any changes were very disruptive on the remainder of the schedule. Furthermore, GOs would have little confidence in the long-range plan. Our goal is to give the GOs more reliable long-range information.  The detailed observing program (SMS2) has typically been specified about 8 weeks in advance of execution.  As a result, it was hard to make late changes, even when they were very well scientifically justified.   Also, there were three or four subsequent scheduling weeks that could be impacted by a change, undoing the work of the planners. For Cycle�5 we are halving the lead time to about four weeks, which makes it possible to support later changes without impact, and which means that only one or two weeks will typically be affected by a late change.  We are currently defining how the revised process will work in detail, and expect to be publishing the new plan in the summer of 1994.

This is an overview of some of the work currently underway within PRESTO, which is progressing simultaneously with normal Cycle 4 science operations. We welcome your feedback and suggestions at any time.



�Mark Johnston, Melissa McGrath

and Ethan Schreier



1 SOGS SPSS is Science Operations Ground System Science Planning and Scheduling 

System



2 An SMS is a Science Mission Specification, the detailed schedule of spacecraft and instrument command requests sent from ST ScI to the control center at Goddard Space 

Flight Center.



Super-sky Flat Fields from WF/PC-1

The Medium Deep Survey Key Project team announces the availability of super-sky flat fields and other calibration files for 

WF/PC-1 which result in improved photometric accuracy.  Exposures of random sky fields have been taken in parallel mode, and used to construct super-sky flats.

The goal of the calibration effort undertaken by the MDS team has been to improve quantitative measurement of faint images.  Several modifications to the standard calibration and image combination procedures have been introduced, including new bias and dark frames, CTE correction for non preflashed data, and super-sky flat fields, with internal pixel-to-pixel rms errors of about 2.4% in F785LP (I) and 2.0% in F555W (V).  Overall, these modifications have improved the quality of faint images by about a factor of five in photometric accuracy and about 0.3 mag in sensitivity.

Detection and quantitative study of faint objects in WF/PC images have been possible by applying the appropriate effort in the calibration process.  The camera is sufficiently stable for good photometric performance (about 1% rms). In order to achieve this performance in both sensitivity and photometric stability, we have augmented the standard 

ST ScI pipeline calibration with some additional procedures.  Noise in the bias and dark frames has been reduced by judicious filtering, which includes removing known patterns and smoothing over scales where nothing but noise appears to be present.  An even more significant improvement is achieved by the use of so-called super-sky flat field images, obtained from a combination of the sky background at many different pointings, instead of Earth flats.  The latter suffer from streaks and non-linearity, and also from large-scale inhomogeneities at the 15-20% level which are difficult to eliminate. Raw sky flats are shown to be repeatably flat at the 1% level over scales of several tens of pixels, and are better suited for faint objects because of the lower level of illumination compared with the Earth flats.  Earth flats are useful in the definition of  high-frequency pixel-to-pixel variations, and have been used in combination with  raw sky flats to generate the super-sky flats.

The MDS calibration procedures result in significant improvements in both photometric accuracy and sensitivity for faint images.  Photometric precision is at least 0.03 mag, or a factor of 5 better than that obtained with standard procedures, mainly because of the use of super-sky flat fields.  Sensitivity is improved by about 0.3 mag, owing to the reduced noise in the calibration files, especially the dark.

A full description of the methods used to generate these calibration files is contained in Ratnatunga et al. (1994) � to be published in the proceedings of the ST ScI Calibration Workshop held in November 1993.

The archived calibration images are listed in the accompanying table.



�Kavan U. Ratnatunga, Richard E. Griffiths, Stefano Casertano,

Lyman W. Neuschaefer

and Eric W. Wyckoff,

Johns Hopkins University



NOW WHAT DO I DO WITH MY HST DATA?

You have made it through proposing, Phase II, scheduling, and observing, and now you have gotten your HST data �what�s next?



The Research Support Branch

The role of the Research Support Branch (RSB) at ST ScI is to help General Observers (GOs) reduce and analyze their data. We can help you in person or remotely, but we encourage all HST GOs, especially first-time GOs, to visit us to learn how to analyze  HST data. 



Science Data Analysts

A visiting GO is assigned a Science Data Analyst (SDA) for the duration of the visit. Our SDA staff is very knowledgeable  about all aspects of HST data and can answer most questions that GOs have. SDAs can also arrange meetings with the instrument scientists or refer the GO to other staff experts on a variety of subjects. SDAs can provide tutorials in Unix, IRAF, and STSDAS if necessary. They can also teach GOs about Routine Science Data Processing (RSDP),  re-calibration, deconvolution, and post-reduction analysis for each of the instruments.



Arranging a Visit for Data Analysis

A typical GO visit lasts about one week, depending on the volume and complexity of the data to be reduced. If the GO is unfamiliar with IRAF or STSDAS, we recommend a longer visit. To arrange your visit,  contact the SDA Coordinator, Krista Rudloff (rudloff@stsci.edu, 410-338-5013). She will discuss your program with you,  ascertain your needs and goals, assign an SDA to help during your visit, and set up a temporary computer account. With written authorization, the SDA Coordinator will also load the data to be analyzed (within reasonable volume limits).

The assigned SDA prepares for the visit by verifying that the account and all hardware and software are functioning properly, reviewing the GO�s goals and the analysis plan with the SDA Coordinator, and checking the quality of the GO�s data. This preparation allows the  SDA to anticipate possible issues or additional needs; due to the time required, we ask GOs to give us two weeks notice in advance of their visit.  



Data Analysis Hotseat

HST GOs can also get prompt data analysis support via phone or email.  Some GOs are able to figure out most of what they need from the documentation we supply but have specific questions about files and  procedures; some GO visitors have follow-up questions after returning to their home institutions; some GOs are simply unable to spend a week  away from their home institution. Whatever the reason, we are happy to answer your data analysis questions remotely.

To contact the RSB Data Analysis Hotseat, email analysis@stsci.edu or phone 410-338-1082. Your question will be answered by the SDA on hotseat duty or referred to the appropriate expert if necessary. If your question requires in-depth research and we cannot answer immediately, you will be kept informed of our progress. 



Feedback

Comments on our user support for data analysis and suggestions for how we could better serve the GO community are encouraged. Please send your remarks to the RSB Data Analysis Hotseat, the SDA Coordinator, or the RSB Chief, Meg Urry (cmu@stsci.edu, 410-338-4593). 



�Krista Rudloff and Meg Urry



HST Archive News

The HST archive was officially opened in February 1993.  In its first year of operation, 24 Gbytes of data were retrieved by astronomers around the world and there are now 315 astronomers (outside the Institute) who have archive accounts which are needed to retrieve data from the archive. There is now public data in the archive for about 5000 different astronomical targets, including a limited number of post-servicing mission observations. In fact, 80% of the archival data is public. The HST archive contains not only the science data from all HST observations, but also all of the calibration files and tables used to calibrate HST observations and much of engineering data from HST. All of these data files can be retrieved.

Since November 1993, astronomers using the HST archive through the archive host machines have been encouraged to use the first release of the new user interface to the HST archive, StarView.  The first release was designed to replace the functionality of STARCAT, which is solely a CRT interface, but the second release, which was installed in March 1994, supports both CRTs and X-windows.  The X-version operates on Sun systems running SunOS or Solaris with OpenWindows or Motif as well as on DEC VAXstations running VMS.

Based on initial comments from users, we believe StarView is significantly more straightforward to use than STARCAT (which we expect to phase out in the spring of 1994 at the Institute).  StarView provides a form-based interface to the most �important� fields in the archive database, as well as access to all of the 1700 fields in the archive database for those with special requirements.  Furthermore, StarView currently supports two special features that should make your life as an HST archive researcher significantly easier.

First, in collaboration with the SIMBAD project in Strasbourg, we have included a name resolver in StarView.  The name resolver allows you to quickly obtain the RA and DEC of an object based on any one of the names which SIMBAD recognizes for that target.  Then you can use the RA and DEC (and a search radius) to search for all of the observations of the object.  This eliminates problems associated with the fact that different observers use different names for the same target, such as NGC 598 for M33, which often make name-based searches of the archive incomplete.

Second, in collaboration with the CADC and ECF, we have added a feature to the X-version of StarView which allows you to preview public data in the archive before deciding whether to retrieve it from the archive.  The preview data is stored and retrieved as part of the database.  For WFPC and FOC, the preview data consists of highly (200x) compressed images which are currently displayed using SAOimage.  For the FOS and GHRS, a complete calibrated spectrum is displayed using a publicly available plotting package called xmgr.

In order to make use of either version of StarView over the network, you simply log into the UNIX host (stdatu.stsci.edu) or VAX/VMS host (stdata.stsci.edu) using your archive host account name and password if you have an account, or username �guest�, password �archive� if you do not.  To start the X version, type �xstarview.�  It will first remind you of the few simple instructions which permit the archive host machine to write to your X display, and then load the program.  Once the program is up and running (which can take a few minutes), you simply point and click as in any other X application. Most first time users will want to try the �quick� search screen first, which provides access to the name resolver described above.  Though we believe StarView is sufficiently intuitive that most users will be able to use it without paper documentation, new versions (4.0) of the Archive Primer and Archive Manual are available from USB (or the archive hotseat).

StarView is a client-server software package.  It is possible for USA and Canadian users to obtain the client for Sun X-windows versions of StarView.  A distributable VMS version is planned.   Running the client on your home workstation should improve performance considerably. Users interested in getting the distributed version should contact the archive hotseat.  The installation procedure is straightforward but, because the archive is changing rapidly at the present time, occasional users of the archive may want to wait to install the distributed version until the fall.

 The development of a new user interface to the archive is part of a larger transition of the archive involving both the user interface and the archive engine which supports user requests.  All HST data to date has been archived to optical disk using a set of prototype hardware and software known as the Data Management Facility.    In September, Loral AeroSys delivered a new archive engine, the Data Archive and Distribution Service (DADS), to the Institute.  Since it was delivered, a group of software engineers have been working to complete the software needed for DADS to replace DMF.  The first major milestone in the DMF to DADS transition took place in December at the time of the servicing mission when operations staff began archiving data from HST to DADS (in parallel to DMF).  The second major milestone occurred in late January, when we began copying data from DMF to DADS.

The next major milestone in the DMF to DADS transition will be to make DADS available to users.  This will most likely occur in late Spring.  We will try to make this as painless as possible, and there should be no interruption in service.  There will be a period of time when both systems will be available to users. During this period, you will be allowed to choose which system you want to use. Your choice will depend upon the data you are seeking since (initially at least), DADS will not have all of the pre-servicing mission data. You will choose which system to work with as part of the start-up process for StarView. If you change your mind about the system you want to use, you will need to log out of Starview and log in again. The reason that you will have to make this choice is that we plan to stop archiving new data into DMF later this Spring. At that point, DMF will no longer contain all of the post-servicing mission data.  On the other hand, the process of transferring pre-servicing mission data to DADS will not be complete until the Fall.  As a result, DADS will not have all the pre-servicing mission data.

DADS has several features which should make using the HST archive simpler and easier. Unlike DMF, DADS stores most data internally as FITS files or FITS tables.  Thus with DADS, it will not be necessary to convert the files for your home computer.  In addition, with DADS you will have the option of shipping files directly to your home computer instead of first staging the data to one of the archive host machines here and then using ftp to get the data.

As a result of all the changes associated with the transition, users will need to be particularly careful to read the news posted on stdatu and stdata during this period.  If you have any problems with the archive, especially during this transition period, please contact the archive hotseat (archive@stsci.edu) and we will do our best to help you.



�Knox Long



HST Users Committee Report

The Committee met in September and January, and also held a 4-day seminar on the HST budget in January. We summarize here the main items of discussion over the past few months. With the extremely successful first servicing mission, principal concerns are over the project budget and  long-term operation of the HST: the present and projected levels of support for HST place the 15 year mission at significant risk, as funding for spacecraft components and future instruments is very limited. In addition, the operations and data analysis budgets are being cut. We have submitted a detailed budget report to the project, and plan to follow developments closely.

    The role of the STUC was discussed and user input is invited on this subject or any user issues, to any of the members. There are three new committee members this year, replacing Hutchings, Kirshner, and Hobbs. The committee members are T. Lauer (chair), P. Feldman (vice chair), R. Weymann, B. Wills, S. Lilly, F. Fusi-Pecci, G. Miley, J. Trauger, T. Snow, W. Freedman, R. Robinson, R. Windhorst. We summarize below the main points from our regular reports:

1. We are impressed and delighted by the success of the First Servicing Mission, and the efficient progress of SMOV. On behalf of the HST users we express our congratulations to all concerned with this operation: instrument teams, the GSFC project management, ST ScI, and the STS61 team and crew. We particularly commend the extraordinary leadership of the project manager Joe Rothenberg and regret to learn that HST will lose his services. We also express our appreciation to Ed Weiler for his long-standing work and support for the HST project.

2. We commend ST ScI and NASA for the timely publicity of the restored HST at the January 1994 AAS meeting.  We note that HST pictures are in great demand for general and professional information.

3. We commend ST ScI for its analysis of OTA breathing and post-servicing mission jitter.  We note that accounting for breathing is likely to be important in many critical applications, such as crowded-field stellar photometry.  We urge ST ScI to alert observers to the integrated effects of breathing, as well as the presence of any strong jitter event in their observations. 

4. We note that both the thermal vac and on-orbit results for the UV throughput of WFPC2 are consistently lower than the handbook values used in Cycle 4 proposal preparation and allocation. We will monitor whether Cycle 4 observing time for the UV with WFPC2 is adequate. We request a summary of WFPC2 filter calibrations.

5. We commend the efficient way in which the comet-Jupiter campaign proposals were handled. We very strongly endorse proposed changes to all proposal submission and processing: particularly the move from hourly to orbit accounting; the establishment of proposal �wizards� to follow a program in its entirety; and the user-interactive approach to Phase II. We urge that these improvements be implemented for Cycle 5.

6. We commend ST ScI for efforts already made to simplify the budget process for GOs, and suggested further reductions in the number of formal budget submissions required of GOs. 

7. The early Cycle carry-over was discussed. We note that all early Cycle PIs should be notified of the completion status of their proposals. We trust that conflicts and problems will be dealt with on an individual basis by Bob Williams. We will monitor this process. Cycle 4 and 5 schedules were discussed and appear to be reasonable. The STUC suggests that the TAC process for Cycle 5 look into ways to improve elimination of conflicts and duplication of observations between the new proposers and approved GTO or GO programs, or archival data.

8. We do not consider that hosting a proposal-briefing workshop is a good use of ST ScI effort. We suggest that a clinic or demo booth at the June AAS meeting might be a worthwhile effort. We note that a science conference on HST results (similar to that in Sardinia in 1992) would be desirable in the summer of 1995.

9. The books of the calibration and restoration workshops of November 1993 constitute a valuable resource for all users. We suggest that they be made as widely available as possible. We request that up-to-date information on data reduction and calibration be mailed with the data products to users. We endorse the work on image restoration, and consider that it should be supported as an ongoing effort.

10. While we discuss the budget extensively in our separate report, we wish to stress that we consider steady and predictable funding for both STIS and NICMOS to be essential for the successful preparation for the Second Servicing Mission.

11. The new method of updating and emailing proposal status is strongly approved. We request an efficient single point contact between users and the Institute, and that calls from users be logged and tracked.

12. The FOS flat field program has been successful. We recommend that users be advised of the status of FOS scattered light removal, and pipeline processing updated. 

  The next STUC meeting is proposed for September 8, 9.



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



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 for 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 acknowledgement 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 for Research in Astronomy, 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

A One Stop Guide to Reducing HST Data 

   The HST Data Handbook, a comprehensive guide to all major aspects of HST data reduction and analysis, is now available.  This Handbook collects all of the information you need to work with HST data  in one place.  It describes how to understand the contents of each dataset, how to read, understand, and display HST images and spectra, how to identify and correct problems in your HST data, and how to perform common analysis and image reconstruction tasks.  The Handbook assume no prior knowledge of HST data, the IRAF or STSDAS systems, or any specific knowledge of HST instruments, other than that required to have prepared your observing proposal.  

  The Handbook is divided into two principal parts, plus a series of appendices. Book I, the HST Cookbook includes the following sections (1) From Tape to Display, (2) Calibration and Recalibration, (3) Analysis, and (4) Image Deconvolution.  Book II, the Instrument Data Book, contains one section for each HST Instrument.  The Instrument sections are designed to prepare you to work with and understand the limitations of the data for a particular HST instrument.  Basic tutorials about using IRAF and STSDAS, accessing the HST Archives, and using STEIS are provided as appendices.

   The HST Data Handbook is currently being shipped to observers along with their data tapes.  It has also been sent to Guest Observers whose observations occurred during the past year.  The HST Data Handbook is  available upon request from the User Support Branch (usb@stsci.edu)  and is available electronically on STEIS.



�Stefi Baum



DIGITIZED OPTICAL SKY SURVEYS AT ST ScI �                 A PROGRESS REPORT

Introduction

The Catalogs and Surveys Branch (CASB) is continuing its program of digitizing sky survey Schmidt plates, in support of HST observation planning and to provide the raw data for a future revision of the Guide Star Catalog.

The motivations for these are to provide guide star positions for HST pointing in the presence of accumulating proper motions and to provide deep all-sky coverage for planning purposes.  The original Guide Star Catalog (GSC) was built using the SERC J survey (epoch circa 1975, limit J=21) and the Palomar �Quick V� survey (epoch circa 1984, limit V=19), which were scanned on modified PDS microdensitometers with a 25 �m sample interval and then processed to build the GSC (see Lasker et al. 1990, AJ, 99, 2019). Simulations of the astrometric errors due to accumulating proper motions predict an increasing acquisition failure rate.  The earlier southern hemisphere survey will be the first to degrade with an expected failure rate of up to 5-10% for the 4.3" FOS aperture by the year 2000. The smaller instrument apertures could fail by as much as 50% unless peak-up acquisition modes are employed. The need for deep all-sky coverage also leads to the need to supplement the Quick-V survey with deeper material. In order to satisfy these requirements, ST ScI is collaborating with Palomar Observatory to scan the original POSS-II plates for the north, and with the AAO to make and scan the SES (second epoch survey) for the south. 



Scanning Machine Enhancements

While the 25 �m sample interval used in GSC-I was a marginal choice for the older Palomar material and a poor choice for the modern materials from both Schmidts, it was required to meet the original GSC schedule imposed by HST mission constraints. As the new scanning is being done under less constraining schedules, we revisited the question of the sampling interval, the goal being to adopt a sample interval which is small enough to collect most of the information from the plate and to perform well with conventional image processing algorithms, while still large enough that the scanning throughput is reasonable. This study (Laidler et al., in 1992 Digitized Optical Sky Surveys, Astrophysics and Space Science Library, 174, 95) recommended the adoption of a 15 �m sampling interval. The mechanical, electronic and optical constraints of the microdensitometers, led to a throughput of about 1 plate in 48 hours compared to 12 hours for first generation scans. While scanning was started in this configuration, it was clear that the throughput had to be improved in order to complete the scanning in the same time scale as the completion of the surveys (1997-8).

A program of hardware modifications to the microdensitometers has been underway for the last year with a corresponding reduction in scan time.  The servo system to control the position of the carriage has been replaced with a modern commercial unit which allows greater precision in the sampling positions. Beam illumination can now be provided by a laser (instead of a halogen lamp) and a new set of optics, removing a speed limitation imposed by the photon noise per sample interval in the regions of high photographic density. These enhancements have reduced scan times to about 29 hours.  The remaining limitations are due to the speed of the ADC (Analogue to Digital Converter) electronics converting the pixel values. A new high speed, low noise ADC is now in testing which will remove this restriction. Finally, a multi-channel capability has been successfully prototyped that will reduce scan times to under 12 hours. This is based on the use of an acousto-optical deflector to move the laser beam perpendicular to the scan direction so that one can sample several lines with one mechanical motion.  The microdensitometers have been so completely modified (except for the granite base) that they are no longer referred to as PDS machines, but as GAMMAs (GSSS Automated Measuring Machines)!



Scanning Program and Archive

Second generation plate scanning has been continuing during the upgrade process and by the end of 1994 we expect to be in full production, processing over 100 plates per month which is sufficient to complete the scanning at the same time as the observatories expect to complete the surveys. The current status is outlined in Table 1.  The scans are subjected to extensive quality assurance to ensure that we obtain an A-grade scan before shipping the original plates back to the observatory. These data are then archived to optical disk and placed in the CASB archive for future use.  Although several other groups around the world are also scanning these plates, we are unique in that we archive the raw pixel data rather than just the processed catalogues.  When there is a significant change in the image processing or analysis, this allows us to reprocess any field completely rather than just using the partial data contained within the previously identified objects. In the areas of the sky which contain extended objects such as nebulae or gaseous filaments, this can be a necessary step. Finding charts (such as those we create for HST GOs) are also easier to use when created from the original digitized pixel data.  Finally, the scan archive will be a valuable resource for future NASA missions.



Image Publication

As was announced in the December 1993 edition of the AAS newsletter, NASA has provided ST ScI with a grant to compress some of this survey data and to provide it to the community as a set of CD-ROMs. The first set of data (the SERC J survey) should be distributed about the time that this newsletter is published with the POSS-I E survey to follow in about a year.  We hope to be able to arrange a similar distribution of the POSS-II and SES surveys soon after they are completed. There are plans to load the compressed scans into the DADS system in the future which will allow access to these data via the usual HST archive channels.



�Brian McLean



STSDAS Release Status

The latest version of the TABLES and STSDAS external packages, V1.3.1, was released in mid-December 1993, and is available on STEIS in the software/tables/updates and software/stsdas/v1.3/updates directories. This patch release featured various enhancements and a few minor bug fixes, which are summarized below. The long-awaited �Users Guide for TABLES and STSDAS� will be available by the time this Newsletter is distributed. Users can request a hardcopy by sending a note to hotseat@stsci.edu, or they can retrieve a Postscript or ASCII text version of the document via ftp from STEIS. The files can be found in the directory software/stsdas/doc/user. The next release, V1.3.2, will be available sometime this spring. 



New and enhanced status

Several new tasks have been added to STSDAS since the V1.3 release, and others have been modified or enhanced. The hst_calib.synphot package, which is used for synthetic photometry and modelling the throughput of the various HST instruments, has benefitted from the enhancement of the expression evaluator. The new syntax is more like FORTRAN, catches more syntax errors, and is easier to use. The table below gives examples of the old and new forms for some common synphot expressions. Detailed information about the new expression evaluator can be found in the on-line help files for the calcband and calcspec tasks, in the package help (type �help synphot opt=sys�), or in an update to the new �Synphot Users Guide� which can be found on STEIS in the directory software/stsdas/v1.3/doc/user/SynphotGuide in the file �Update1.ps�.

Users who are preparing Cycle 5 proposals should be aware that some component tables (i.e., the tables that describe the instrument response and filter transmission curves) have been revised, particularly those for WFPC2. External sites may obtain the latest component tables from STEIS: see the README file in the cdbs directory for the file locations. 

Some new tasks, as well as enhanced versions of existing tasks, have been added to the hst_calib.fos.spec_polar package. This package contains tasks tailored to the processing and analysis of FOS spectropolarimetry datasets. Capabilities include examination of both flux-calibrated and polarimetry spectra, averaging of multiple datasets (either at the stage of flux-calibrated spectra or polarimetry spectra), rebinning of polarimetry spectra, and computation of polarimetry spectra from flux-calibrated spectra. The calpolar, pcombine, polave, polbin, and polplot tasks have all been enhanced since V1.3, and three new tasks have been added. They are: comparesets for producing a stacked plot of flux-calibrated spectra to compare spectra obtained at different waveplate positions and the identification of bad data; plbias which corrects for bias in linear polarization (PL) spectra; and polcalc which computes polarization spectra from flux-calibrated datasets. A tutorial on FOS spectropolarimetry datasets and their processing/analysis using the fos.spec_polar tasks is available on-line by typing �help spec_polar opt=sys�.

The hst_calib.wfpc package has also been enhanced to accommodate WFPC2 calibration and analysis. The RSDP calibration pipeline, calwp2, has been enhanced to compute various statistical quantities in the science data header. These quantities are most useful for evaluating the quality of WFPC2 data before the images are retrieved from the HST archive. Some existing tasks in the wfpc package, which were designed to work on WFPC data, are also useful for WFPC2 data: combine, noisemodel, and wstatistics. Other tasks, including engextr, have recently been modified to work on WFPC2 data as well. The remaining tasks, including metric, wfixup, and wmosaic, will be modified soon, but in the mean time will print out an appropriate warning if they are not compatible with WFPC2 data. 

A new task has been added to the wfpc package for rejecting cosmic rays. This task, crrej, works best if you have many exposures of the same target. It is particularly useful for building calibration reference files, where the need to reject outlier values exceeds the need to preserve the noise characteristics of the input data. The task uses an iterative scheme, beginning with modest rejection thresholds, and uses �sympathetic rejection� to detect neighboring pixels (in two dimensions) that may have been affected by the cosmic ray event.  The rejected input pixel values are flagged, and the rejection threshold is adjusted (usually, tightened) for adjacent pixels; the process is repeated for each user-specified rejection threshold. Note that the criteria for pixel rejection (the �sigma� in �sigma-clipping�) is based upon the noise properties (i.e., the read noise and the scale noise of the data), as it is for the CRREJ option in the combine task. Also note that rejection is performed on BOTH the high and low side of the median value, so that this task in reality removes not just cosmic rays, but all outlier values. 



Upcoming Packages & Tasks 

A package called nebular has been developed to derive (i) the physical conditions in a low-density (nebular) gas given appropriate diagnostic emission line ratios, and (ii) line emissivities given appropriate emission line fluxes, the electron temperature and density. The tasks in this package are based on the 5-level atom program developed by DeRobertis, Dufour & Hunt (1987, JRASC, 81, No. 6, 195). These tasks extend the functionality of the original FIVEL program to provide diagnostics from a greater set of emission lines, most particularly those in the vacuum ultraviolet that are now available from the IUE and HST archives. 

Two of the tasks also provide a very simple model within which to derive the nebular ionic abundances. They also make use of STSDAS binary tables for efficient access to the input fluxes and the output diagnostics and ionic abundances. These tasks are most useful for calculating nebular densities and temperatures directly from the traditional diagnostic line ratios, either to provide some reasonable input parameters for a more complicated physical model, or to calculate ionic abundances (or other quantities) within some simplifying assumptions. This package is still under development, which is why it debuts under playpen, rather than under analysis. As it is more fully developed, it will include tasks for deriving interstellar reddening, calculating ionic abundances from recombination lines, and calculating nebular continuum. 

Two new tasks, xyztoim and xyztable, have been added to the toolbox.imgtools package in STSDAS. These perform a similar function, but xyztoim creates an image and xyztable creates a table. Both tasks read a table or text file containing three columns, X and Y independent variables and a Z dependent variable (hence the �xyz� in the task names). A polynomial surface is fit to Z as a function of X and Y, and the fit is evaluated to obtain the values to write to the output image or table. An example of how this task might be used is the determination of how the variable PSF in WFPC data affects aperture photometry. In this case, the X and Y variables would be the position in the image of a large number of stars (e.g., from an observation of w Cen), while the Z variable would be the measured magnitude within a given aperture to the total instrumental magnitude.

A new task is in the works for combining multi-dimensional images with a variety of pixel rejection criteria. The task, called gcombine will be modelled after the IRAF images.imcombine task, but will retain a few of the features of the wfpc.combine task. That is, the logical separation of pixel rejection and combination/weighting algorithm will be much like imcombine, but the ability to loop through all groups of a GEIS image, and to make use of HST data quality files (DQFs) will be preserved. This task should be ready for the next release. 



New Information Services 

Two new utilities are available to provide information via the Internet about STSDAS. Users of World Wide Web can now access a home page for STSDAS (the URL is: http://ra.stsci.edu/STSDAS.html). This home page can also be accessed from the Institute WWW home page. This utility is a good way to find general information about obtaining, installing, and using TABLES and STSDAS. It also provides users with information about release status, advice on configuration, and available documentation. 

A new USENET newsgroup for astronomical data analysis software is now available at several major IRAF sites. This consists of a collection of newsgroups organized as a USENET alternate news hierarchy called �adass�; the subgroups �iraf.announce�, �iraf.applications�, �iraf.buglog�, �iraf.programming�, �iraf.sources� and �iraf.system� are intended to provide the community with rapid access to new developments and current issues about all the major IRAF layered packages, including STSDAS and TABLES. This service has been in alpha-test for a few months, and will be available to all external sites in the near future. If your site would be interested in setting up this newsgroup, please contact the STSDAS Group, or the IRAF Group at NOAO. 



ADASS Coming to Baltimore

The annual conference on Astronomical Data Analysis Software and Systems (ADASS) has, in only a few years, become the premier forum for the presentation and discussion of algorithms, software, and software systems employed in the reduction and analysis of astronomical data. ST ScI will host this year�s conference, which will be held at the Omni Inner Harbor Hotel in Baltimore on 25-28 September. This event is sponsored by the Dominion Astrophysical Observatory, National Optical Astronomy Observatories, Smithsonian Astrophysical Observatory, ST ScI, and by NASA and NSF. 

The conference program will include invited and contributed talks, and contributed posters and demos. Key topics this year include astronomical data modelling and analysis, graphical user interface (GUI) design, network information systems, and parallel and distributed computing. The Program Organizing Committee members are Rudi Albrecht (ST-ECF/ESO), Rodger Brissenden (SAO), Carol Christian (CEA), Tim Cornwell (NRAO), Dennis Crabtree (CADC), Daniel Durand (CADC), Bob Hanisch (ST ScI), Rick Harnden (SAO), George Jacoby (NOAO), Barry Madore (IPAC), Dick Shaw (ST ScI), Karen Strom (U. Mass), and Doug Tody (NOAO). 

If you would like more information, please see the the WWW home page (�http://ra.stsci.edu/ADASS.html�) or send e-mail to softconf@stsci.edu. You may also contact Betty Stobie, who is Chair of the Local Organizing Committee, at (410) 516-8671, or by FAX at (410) 516-6864. 



�Dick Shaw



STEIS Meets the World Wide Web

The Space Telescope Electronic Information System (STEIS) is now accessible via the World Wide Web (WWW).   The World Wide Web (WWW or W3) is a hypertext-oriented way of navigating the Internet and accessing information. Hypertext is text which contains links to other documents.  The WWW project originated at CERN (the European Laboratory for Particle Physics). 

There are several benefits to accessing STEIS via the WWW instead of Gopher:



More information is accessible



In the WWW version of Astronomical Internet Resources there are over 60 resources available which are not accessible via Gopher.



More powerful user interface



The WWW user is presented with a hypertext document which can contain figures, and data entry forms, along with text and pointers to other resources.  This presentation is much more powerful than the Gopher menu or form or text presentation.  

STEIS uses the richer presentation

style to:



Display post-COSTAR images along with

descriptive text



Provide explanatory text for pointers to

external resources



Provide explanatory text for search tools.



Access to WWW is obtained by running client software on your local host. The client allows you to read hypertext documents which are made available at individual internet sites (such as STEIS) and to navigate from document to document by fetching the selected hypertext documents. 

The recommended WWW client for X-Windows workstations is Mosaic which is available from NCSA.  The recommended client for VT100 terminals is Lynx which is available from the University of Kansas.  For more information about WWW clients, look at the file

	.WWW-FAQ



in the STEIS top level directory.



To access STEIS via WWW, invoke Mosaic or Lynx with the parameter



http://stsci.edu/top.html



e.g.,



Mosaic http://stsci.edu/top.html

lynx http://stsci.edu/top.html



Both of these clients have excellent online documentation.



�Chris O�Dea and Bob Jackson





AURA NEWS

Dick Malow Joins AURA

 AURA is pleased to announce the appointment of Mr. Richard N. Malow as Special Assistant to the President for International Relations.

Malow left his post as the Clerk of the VA, HUD, and Independent Agencies Subcommittee of the House Appropriations Committee in January.  During his 21 years on Capitol Hill, Malow had responsibility for more than 70 appropriations accounts for 20 Federal agencies, including the National Science Foundation and NASA.  Formerly, Malow served in management positions in the Department of Agriculture and the Overseas Development Council.  

Malow will join the AURA Corporate Office officially on April 1, 1994.



�Goetz Oertel, AURA

 

AURA ACHIEVEMENT AWARDS

 AURA is pleased to announce the ST ScI recipients of its 1993 annual awards for outstanding science and service to the astronomy community.  

Marc Postman received AURA�s Science Award for his research into the large scale structure of the universe.  In particular, and in collaboration with Tod Lauer of NOAO, Marc has measured the velocity of the Local Group with respect to an inertial frame defined by the 119 Abell and ACO clusters contained within 15,000 km/s.  This is the deepest volume limited radial velocity survey yet conducted.  Distances to the clusters are determined by an analysis of the radial brightness profiles of the brightest cluster members.  

Barry Lasker received AURA�s Service Award for the design and implementation of the Guide Star Selection System in support of HST operations.  Barry led the Guide Star Software and Scanning effort to produce a catalog of the brightness and position of over 20 million stars in time for a 1986 launch of HST.  Barry has also played a major role in the conceptual stage of the Image Compression Project, which is compressing the complete scanning data obtained from the original project and new scans of the original 1950 epoch Palomar E plates.  This project will eventually provide a compact disk album containing a digital image of the entire sky.

 Congratulations!



�Goetz Oertel and

Lorraine Reams, AURA





INSTITUTE NEWS

SYMPOSIA AND WORKSHOPS

The annual ST ScI May Symposium, The Analysis of Emission Lines, A Meeting in Honor of the 70th Birthdays of D.E. Osterbrock and M. J. Seaton, will be held at the Institute on May 16-18, 1994. The topics to be covered include: A Historical Perspective, Atomic Data & Cross Sections, Radiative Transfer, Shocks, Photoionization, Expanding Atmospheres, Eclipse Mappings & Reverberation, X-Ray Plasmas, IR and UV Spectroscopy, Molecular Line Diagnostics, Abundance Determinations, Winds, Line Diagnostics, Gamma Ray Lines and Spectropolarimetry. For information contact Cheryl Schmidt at (410) 338-4404 or send e-mail to symposia@stsci.edu. 

The Institute will also hold two Mini-Workshops:

1)  Quantifying Galaxy Morphology at High Redshift, to be held April 27-29, 1994 at the Institute. Topics will include: Quantitative Morphology at Low z, Robust Techniques for Measuring the Morphology at High z, Field Galaxy Evolution, Cluster Galaxy Evolution and Ultra High Redshift Galaxies.  For information contact ferguson@stsci.edu..

2) Dust Survival in Interstellar/Intergalactic Media, will be held on July 13-15, 1994 at the Institute. Topics will include: Dust Composition in Different Interstellar Environments, Dust Formation/Destruction, Dust Extinction and its Dependence on the Environment, Dust Content and Distribution in Galactic and Extragalactic Objects, Intergalactic Dust, Dust in Cooling Flows, Dust in Damped Lya Systems and Extinction of QSOs Behind Clusters.  For information contact calzetti@stsci.edu.. 



�Mario Livio



ESA FELLOWSHIPS

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 interests of staff members at ST ScI can be obtained from Dr. N. Panagia.  Details of the fellowships and applications procedures can be obtained from the EDUCATION OFFICE, ESA, 8�10 rue Mario Nikis, 75738 PARIS 15, FRANCE. 

Completed application forms must be submitted through the appropriate national authority, and should reach ESA no later than 31 March for consideration in May, and no later than 30 September for consideration in November.

A copy of the completed application should be sent to the Chairman of the Postdoctoral  Selection Committee (currently Dr. M. Fall) at ST ScI, 3700 San Martin Drive, Baltimore, MD21218, USA. 

Selected Fellows must negotiate the commencement dates of their ESA Fellowships at ST ScI with the University Programs Division (c/o Nino Panagia) at least two months before their prospective starting dates. 

The interests and activities of staff members at ST ScI can best be assessed by reading the annual report of the Institute which is to be found in the Bulletin of the American Astronomical Society (1994) Vol. 26, p. 617.



�Nino Panagia



THE 1994 HUBBLE FELLOWSHIP PROGRAM

For Cycle 5, the award process for the Hubble Fellowship Postdoctoral Program was an intensely competitive one, with the application pool one of the largest ever to be received since the inception of the program in 1990.  This year 168 applications were accepted from highly qualified candidates of all nationalities who had earned a doctorate degree after January 1, 1991, in Astronomy, Physics, and related disciplines.  These candidates were considered in depth by a 10-member review panel in mid-January to determine which scientists would be selected for the 11 available Hubble Fellowship awards funded by NASA for this Cycle.  Upon review and approval by the ST ScI director Bob Williams, notifications of awards were made by February 1 with replies due by February 15.  All awards were accepted by the 11 original candidates.  These 1994 Hubble Fellowship recipients have been listed below along with their designated Host Institution.

The Hubble Fellowship Program is a joint venture between NASA and ST ScI in cooperation with those astronomical institutions across the United States electing to participate in the program.  The program provides a limited number of recent postdoctoral scientists of unusual promise and ability with the opportunity to pursue the HST related research of their choice at a participating U.S. astronomical institution designated as Host institution by the scientist.  Candidates are selected each year by a review panel which ranks them on the basis of merit (research proposal, publications, academic achievements) after which the ST ScI Director or his designate approves the final awards.  To promote a distribution of research activity among a larger number of institutions, no more than one Fellow per year is approved for any one academic location.  The duration of a Fellowship runs for a total of three years, which period includes an initial two year appointment with an extension to a third year granted after a positive mid-term review.  Currently the program supports a pool of several dozen astronomers.

The Hubble Fellowship Program is expected to play an important role in expanding and strengthening the research work of the astronomical community.  Upon completion of the Fellowship Program, these young astronomers are expected to go on to professorships at a wide variety of major institutions.  Peter Stockman, the deputy director of ST ScI notes that �the Hubble Fellowships not only fund excellent scientific research, but also bring the best and brightest into the nation�s centers of higher education.�  He further says that �we expect that many of the Hubble Fellows will become tomorrow�s top scientists and educators.�

It is anticipated that the Announcement of Opportunity for the 1995 round of Hubble Fellowships will be issued in early summer of 1994.  The deadline for submitting applications is projected to be mid-November 1994. 



�Lisa Spurrier and Colin Norman



SABBATICAL VISITORS AT ST ScI

This year, we have welcomed three sabbatical visitors to ST ScI. Dr. Patrick Harrington�s (University of Maryland) main area of interest is photoionization models, and their application to planetary nebulae. Dr. Andrei Illarionov (P. N. Lebedev Institute, Moscow) has worked on the theories of Comptonization and X-ray sources and also in the area of cosmology. Dr. Illarionov is spending a year in the U.S., having visited the University of Colorado and Johns Hopkins University before coming to ST ScI. Dr. Dina Prialnik-Kovetz comes to us from Tel Aviv University. Her main area of astronomical research is cataclysmic variables.



�Andrew Wilson



RECENT STAFF CHANGES

DAVE BAXTER, former Sr. Scientific Software Analyst in SPD, left the Institute in February.



SCOTT BINEGAR, Software Systems Engineer, joined the Institute staff in October.  Scott was a Computer Scientist at CSC in Rockville, MD.



JESUS BURGOS-MARTIN, Graduate Student in UPD, joined the Institute in September.  Jesus was a graduate student at the Instituto de Astrofisica de  Canarias in the Canary Islands.



BRIAN CAMUS, former Sr. Software Systems Engineer in SESD/OSB, left the Institute in October.



Michael Dahlem, former Postdoctoral Fellow in UPD, left the Institute at the end of December 1993, to migrate over to Johns Hopkins University.



MARK DICKINSON, AURA Postdoctoral Fellow in UPD, joined the Institute staff in January.  Mark was a Ph.D. student at the University of California at  Berkeley.



MEGAN DONAHUE has started her appointment as an AURA Postdoctoral Fellow in UPD in  September.  Megan was previously a Carnegie Fellow at the Observatories of the Carnegie Institution  of Washington in Pasadena, California.



HENRY FERGUSON, who was formerly a Postodoctoral Fellow at University of Cambridge, UK, started his appointment as a Hubble Fellow in UPD in late August 1993.



ANDREW FRUCHTER, Assistant Astronomer in SCARS/DSOB, joined the Institute staff in December.  Andrew was a Hubble Fellow at the University of California at Berkeley.



MAURO GIAVALISCO, who has been an ESA Fellow in UPD for two years, moved in October 1993 to SPD as a Postdoctoral Fellow to collaborate with Bill Sparks and Duccio Macchetto on high-redshift galaxies.



PAOLA GRANDI, former PostDoc in SCARS/RSB, left the Institute in October.



PURAGRA (�RAJA�) GUHATHAKURTA, new Assistant Astronomer in UPD, joined the Institute in early January, 1994. Raja was most recently a Hubble Fellow at Princeton University. 



FRANCESCO HAARDT, a Graduate Student in SPD/USB, joined the Institute staff  in February.  Francesco is a Ph.D. candidate at the International School for  Advanced Studies/SISSA in Trieste, Italy.



PATRICK HARRINGTON has finished his appointment as Sabbatical Visitor in February 1994.  He is returning to his home institution, the University of Maryland, College Park. 



CAROLE HASWELL, former Postdoctoral Fellow in SPD/SIB, left the Institute in  January.



Sherie T. Holfetz, the FGS Technical Assistant, has been promoted to TA II from TA I.



PAUL LEE, Science Data Analyst, joined the SCARS/RSB staff in October.  Paul  was previously a Postgraduate Researcher at the Laboratory for Experimental  Astrophysics at LLNL in Davis, CA.



KEITH HORNE, former Astronomer in SPD/SIB, has been on leave from the Institute since September.



Andrei Illarionov, from Lebedev Physical Institute, Moskow, Russia, joined UPD as a Sabbatical Visitor in mid-February 1994, for a 5-month stay. 

KIP KUNTZ, former Science Data Analyst II in SCARS/RSB, left the Institute in  August.



Claus Leitherer has joined the SIB GHRS team as an Instrument Scientist.



STEPHAN MARTIN, Scientific Programmer, joined the SCARS/DSOB staff in August.  Stephan was previously a Teaching Assistant at the University of Wyoming�s  Department of Physics in Laramie, Wyoming.



Gerhardt Meurer, former Postdoctoral Fellow in UPD, left the Institute at the end of December 1993, to migrate to Johns Hopkins University.



JANE MORRISON, Scientific Programmer, joined the Institute staff in SCARS/SSB  in September.  Jane was previously a Teaching Assistant at the University of  Florida in Gainesville, Florida.



ANNA PASQUALI, a Graduate Student in SPD/SOB, joined the Institute staff in  February.



JOE PESCE, Postdoctoral Fellow in SCARS/RSB, joined the Institute staff in  November.  Joe recently completed his Ph.D. at SISSA/International School for  Advanced Studies in Trieste, Italy.



Dina Prialnik-Kovetz, a Sabbatical Visitor from Tel Aviv University, Israel, has joined UPD in mid-February 1994. She will be at the Institute until early August. 



JON SAKEN, Postdoctoral Fellow in SCARS/DSOB, joined the Institute staff in  August.  Jon was most recently a Research Assistant for the University of  Colorado.



Cheryl Schmidt has become the new Visitors and Workshop Coordinator in UPD as of the beginning of October 1993. 



Salvatore Scuderi, who recently earned his PhD from University of Catania, Italy, joined UPD at the beginning of March 1994, as a new ESA Fellow.



MARK SIMKO, former Systems Manager in OPS/COB, left the Institute in January. 



SHON VICK, former Computer Scientist in SESD/APSB, left the Institute in  December.



YIPING WANG, Research Support Scientist in SPD/SPB, joined the Institute staff in January. Yiping was most recently a student and Research Assistant  at the University of Arizona.



William Welsh, who was a Graduate Student in UPD and earned his PhD in late Fall 1993, left the Institute to start a Postdoctoral appointment at the University of Keel, UK.



FELIX YEN, former Sr. Software Engineer 

in SESD/APSB, left the Institute in 

November.



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.



763.  �A Search for Wolf-Rayet Stars in Active Star Forming Regions of Low-Mass Galaxies:  GR 8, NGC 2366, IC 2574 and NGC 1569,� L. Drissen, J-R. Roy, A.F.J. Moffatt.

 

764.  �Accretion Disks in Cataclysmic Variable Stars:  Recent Observational Developments,� K. Horne.

 

765.  �HST Discovery of Candidate Young Globular Clusters in the Merger Remnant NGC 7252,� B.C. Whitmore, F. Schweitzer, C. Leitherer, K. Borne, C. Robert.

 

766.  �A Determination of the Distance to the High Velocity Cloud Complex M,� L. Danly, C.E. Albert, K.D. Kuntz.



767.  �Detection of [O II] l2471 from the Io Plasma Torus,� M.A. McGrath, P.D. Feldman, D.F. Strobel, H.W. Moos, G.E. Ballester. 



768.  �Are the Observed Frequencies of Double Degenerates and SN Ia Contradictory?� L.R. Yungelson, M. Livio, A.V. Tutukov, R. Saffer.



769.  �Spectroscopy and Photometry of Companion Stars 2 and 3 to Supernova 1987A,� N.R. Walborn, M.M. Phillips, A.R. Walker, J.H. Elias.

 

770.  �Disks and Jets in Planetary Nebulae,� Noam Soker, Mario Livio.

 

771.  �Focus History of the Hubble Space Telescope �Launch to May 1993,� H. Hasan, C.J. Burrows, D.J. Schroeder.



772.  �Imaging the Bipolar Nebula around HM Sagittae,� W.J. Hack, F. Paresce.

 

773.  �On the Distance Determination and Ionization of the High Velocity Clouds,� A. Ferrara, G.B. Field.



774.  �The Structure of the Inner Eastern Spiral Arm of M83,� E.W. Deutsch, R. Allen.



775.  �3- to 13-�m Spectra of Io,� K.S. Noll, H.B. Hammel, L. Young, J. Joiner, J. Hackwell, D.K. Lynch, R. Russell.

 

776.  �Kiloparsec-Scale Radio Emission in Seyfert Galaxies; Evidence for Starburst-Driven Superwinds?� S.A. Baum, C.P. O�Dea, D. Dallacassa, A.G. deBruyn, A. Pedlar.



777.  �HST Observations to the [O III] Emission Line Region in MRK 78,� A. Capetti, F. Macchetto, W.B. Sparks, A. Boksenberg.

 

778.  �Absorption in Three Intrinsically Faint Quasars:  Q0009-016, Q0347-241, and Q2116-358,� P. Moller, P. Jakobsen, M.A.C. Perryman.



779.  �Starbursts, Quasars, and their Enviroments,� T.M. Heckman.



780.  �A Search for Solar-Like Oscillations in the Stars of M67 with CCD Ensemble Photometry on a Network of 4m Telescopes,� R.L. Gilliland, T.M. Brown, H. Kjeldsen, J.K. McCarthy, M.L. Peri, J.A. Belmonte, I. Vidal, L.E. Cram, J. Palmer, S. Frandsen, M. Parthasarathy, L. Petro, H. Schneider, P.B. Stetson, W.W. Weiss.

 

781.  �Detection of CO Cameron Band Emission in Comet P/Hartley 2 (1991 XV) with the Hubble Space Telescope,� H.A. Weaver, P.D. Feldman, J.B. McPhate, M.F. A�Hearn, C. Arpigny, T.E. Smith.

 

782.  �Constraints on Molecular Gas in Cooling Flows and Powerful Radio Galaxies,� C.P. O�Dea, S.A. Baum, P.R. Maloney, L.J. Tacconi, W.B. Sparks.



783.  �A Comparison between Observed and Predicted Mass-Loss Rates and Wind Momentum of O Stars,� C. Leitherer, H.G.L.M. Lamers.



784.  �Jets in Active Galactic Nuclei,� C.M. Urry.



785.  �Hubble Space Telescope Observations of Synchrotron Jets,� W.B. Sparks, J.A. Biretta, F. Macchetto.

 

786.  �The Stellar Population in the Core of M15,� G. DeMarchi, F. Paresce.

 

787.  �Hubble Space Telescope Observations of Active Galaxies,� I.N. Evans, H.C. Ford, G.A. Kriss, Z. Tsvetanov.



788.  �Constraints on Accreting, Isolated Neutron Stars from the ROSAT and EUVE Surveys,� P. Madau, O. Blaes.



789.  �Signatures of UV and Optically Emitting Accretion Disks,� A.L. Kinney.

 

790.  The Ionization Cones in the Seyfert Galaxy NGC 5728,� A.S. Wilson, J.A. Braatz, T.M. Heckman, J.H. Krolik, G.K. Miley.

 

791.  �Discovery of Cepheids in IC 4182:  Absolute Peak Brightness on SN Ia 1937C and the Value of H0,� A. Saha, L. Labhardt, H. Schwengeler, F.D. Macchetto, N. Panagia, A. Sandage, G.A. Tammann.



792.  �On the Interpretation and Implications of Nova Abundances,� M. Livio, J.W. Truran.



793.  �Axisymmetric Outflows from Single and Binary Stars,� M. Livio; �High Resolution Coronographic Imaging and Echelle Observations of S119:  A New Luminous Blue Variable?� A. Nota, L. Drissen, M. Clampin, C. Leitherer, A. Pasquali, C. Robert, F. Paresce, M. Robberto.



794.  �Interstellar and Intergalactic Mg and Na Absorption toward SN 1993J,� D.V. Bowen, K.C. Roth, J.C. Blades, D.M. Meyer.



795.  �Hubble Space Telescope Observations of AGN,� F. Macchetto.

 

796.  �High Resolution Far-Infrared Observations of the Ring Nebula,� C.Y. Zhang, P.M. Harvey, B.J. Smith, C. Colome, J. DiFrancesco.

 

797.  �Dynamics of cD Clusters of Galaxies II. Analysis of 7 Abell Clusters,� W.R. Oegerle, J.M. Hill.



798.  �HST Eclipse Mapping of Dwarf Nova OY Car in Quiescence:  an �Fe II Curtain� with Mach ~-- 6 Velocity Dispersion Veils the White Dwarf,� K. Horne, T.R. Marsh, F.H. Cheng, I. Hubeny, T. Lanz.



799.  �Extinction, Ejecta Masses, and Radial Velocities of Novae,� R.E. Williams.



800.  �Galaxies with Extreme IR and FE II Emission. I MRK 231:  the Signature of a Young IR QSO,� S. Lipari, L. Colina, F. Macchetto.

 

801.  �Binary Nuclei of Planetary Nebulae,� H.E. Bond; �Asteroseismology of Planetary Nebula Nuclei,� H.E. Bond, R. Ciardullo, S.D. Kawaler.



802.  �The O3 Stars in 1993,� N.R. Walborn.

 

803.  �Neutral Hydrogen Absorption in NGC 1068 and NGC 3079,� J.F. Gallimore, S.A. Baum, C.P. O�Dea, E. Brinks, A. Pedlar.



804.  �Unification of BL Lac Objects and FR 1 Radio Galaxies,� C.M. Urry, P. Padovani.

 

805.  �Radio Emitting Dust in the Free Electron Layer of Spiral Galaxies:  Testing the Disk/Halo Interface,� A. Ferrara, R.-J. Dettmar.

 

806.  �Star Spots and the Period Gap in Cataclysmic Variables,� M. Livio, J.E. Pringle.

 

807.  �Some Aspects of the Evolution of Strongly Interacting Binary Stars,� M. Livio. 



808.  �Making Non-Massive O-Ne-Mg Rich White Dwarfs in Cataclysmic Binaries,� M.M. Shara, D. Prialnik; �The Masses of White Dwarfs in O-Ne-Mg Novae:  Observational Constraints, Galactic 26Al, 22Na 

g-Rays, and M31 Novae,� M.M. Shara.

 

809.  �Geometry and Physical Conditions in the Stellar Wind of AG Carinae,� C. Leitherer, R. Allen, B. Altner, A. Damineli, L. Drissen, T. Idiart, O. Lupie, A. Nota, C. Robert, W. Schmutz, S.N. Shore.



810.  �Massive Stars in Starburst Galaxies and the Origin of Galactic Superwinds,� C. Leitherer.

 

811.  �Gravitational Instability and Disk Star Formation,� B. Wang, J. Silk. 

 

812.  �The Star-Forming Histories of Dwarf Elliptical Galaxies,� H.C. Ferguson.

 

813.  �Extended X-Ray Emission in Seyfert Galaxies,� A.S. Wilson.

 

814.  �Ionization Cones and Radio Ejecta in Active Galaxies,� A.S. Wilson, Z.I. Tsvetanov. 



815.  �Obscuration, Orientation, & the Infrared Properties of Radio-Loud Active Galaxies,� T.M. Heckman, C.P. O�Dea, S.A. Baum, E. Laurikainen.

 

816.  �Contributions to the Third Annual Conference on Astronomical Data Analysis Software and Systems,� S.A. Baum, K. Borne, H.A. Bushouse, R.J. Dufour, J.D. Eisenhamer, P. Greenfield, R.J. Hanisch, J.E. Hayes, J.-C. Hsu, S.J. Hulbert, R.E. Jackson, Z.G. Levay, K.S. Long, G. Miller, H. Payne, J. Pollizzi, R.A. Shaw, R.D. Semmel, D.P. Silberberg, B. Simon, E.B. Stobie, D. Swade, R.L. White, J. Williams, R.L. Williamson, N. Wu, F. Yen.



817.  �HST Observations of 3C449:  Discovery of an Extended Nuclear Disk and of Possible Optical Jets,� A. Capetti, F. Macchetto, W.B. Sparks, G.K. Miley.

 

818. �Optical Spectroscopy of Inhomogeneities in the Winds of Wolf-Rayet Stars,� C. Robert.

 

819.  �Eclipse Mapping of the Accreting Magnetic White Dwarf in DP Leo with HST,� H.S. Stockman, G.D. Schmidt, J. Liebert, J.B. Holberg.

 

820.  �HST Images of the Seyfert Galaxies NGC 5929 and MCG 8-11-11,� G.A. Bower, A.S. Wilson, J.S. Mulchaey, G.K. Miley, T.M. Heckman, J.H. Krolik.

 

821.  �The Reddening Law Outside the Local Group Galaxies:  the Case of NGC 7552 and NGC 5236,� A.L. Kinney, D. Calzetti, E. Bica, T. Storchi-Bergmann.



822.  �Dust Extinction of the Stellar Continua in Starburst Galaxies:  the Ultraviolet and Optical Extinction Law,� D. Calzetti, A.L. Kinney, T. Storchi-Bergmann.

 

823.  �UV to Near-IR Spectral Distributions of Star-Forming Galaxies:  Metallicity and Age Effects,� T. Storchi-Bergmann, D. Calzetti, A.L. Kinney.



824.  �Possible Identification of a Cluster of Galaxies at Redshift Z=3.4,� M. Giavalisco, C.C. Steidel, A.S. Szalay.

 

825.  �Narrow-Band Imaging of Fields around Optically-Thick Absorption Systems:  the Line-of-Sight towards 0000-2619,� M. Giavalisco, F.D. Macchetto, W.B. Sparks.



HOW TO CONTACT ST ScI

Telephone: 410-338-4700 

(reception); 410-338 + 4-digit extension of staff member

Fax: 410-338-4767

Mail: 	ST ScI

	3700 San Martin Drive

	Baltimore, MD 21218

	USA

E-mail: Most staff members at ST ScI can be reached on NSI/DECnet and Internet. Address formats are:

NSI/DECnet: stscic::userid

		or 6559::userid 

Internet:	userid@stsci.edu



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



userid%stsci.edu@internet



With few exceptions the userid is the staff member�s surname. Many are published in the Membership Directory of the American Astronomical Society. If you do not know the userid, please send the mail to the User Support Branch (userid USB), which will forward it. The USB is the central point of contact for scientists who wish to conduct research with HST.







LIST OF PREVIOUS ST ScI NEWSLETTER ISSUES

Vol. 1, 1984: No. 1, March; No. 2, June ;

	No. 3, September; No. 4, December



Vol. 2, 1985: No. 1, March; No. 2, June ;

	No. 3, October



Vol. 3, 1986: No. 1, January; No. 2, April ; 		No. 3, July; No. 4, October



Vol. 4, 1987: No. 1, January; No. 2, April ; 		No. 3, July; No. 4, October



Vol. 5, 1988: No. 1, February; No. 2, May ; 		No. 3, July; No. 4, December



Vol. 6, 1989: No. 1, April; No. 2, August ; 		No. 3, November



Vol. 7, 1990: No. 1, March; No. 2, August; 		No. 3, December



Vol. 7, 1990: No. 1, March; No. 2, August; 		No. 3, December



Vol. 8, 1991: No. 1, March; No. 2, June;

	No. 3, November



Vol. 9, 1992: No. 1, March; No. 2, October



Vol. 10, 1993: No. 1, March;

	No. 2, September