Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/STSCI/JUNE91.TXT

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THE HST OBSERVATORY

From the Director's Office


After a prolonged period of commissioning and early science
observations, the Cycle 1 General Observer (GO) and Guaranteed Time
Observer (GTO) science programs have begun. In May, responsibility
for constructing the science mission of HST was transferred from
NASA to STScI. While many of the formal Science Verification
calibration programs will be completed in the next six months under
NASA coordination, this formal transition was a natural and
important step in the HST mission. Both the ground elements at GSFC
and science mission operations at the STScI have proven their
capability to operate the spacecraft in a routine fashion as well as to
recover from unforeseen problems. Currently, astronomical
observations are being defined months before their execution in
order to improve the efficiency of telescope usage and to coordinate
satellite communications with other NASA facilities. However, for
scientific targets of opportunity and unforeseen difficulties, the GSFC
and STScI systems have been able to respond rapidly and with a
minimum impact upon the preplanned science program.


A recent example was the response to a failed flight-computer
memory board, which led to a deep safing of the observatory and
loss of communications. As described in Rodger Doxsey's article
below, the controllers were able to restore normal operations within
five days - just in time to initiate a time-critical science observation
of the flare star AD Leonis carried out in coordination with ROSAT!

As the first cycle of science observations begins, members of the
astronomical community are already preparing their proposals
(including proposals for Archival Research) for Cycle 2, which will
start in July 1992. Although Cycles 2 and 3 will not enjoy the
improved imaging that we expect to obtain later when the corrective
optics are installed, we do anticipate that these new programs will be
better matched to the HST's current optical performance.

Over one hundred astronomers participated in the May HST
Workshop: "The Year of First Light." During the workshop, dozens of
scientific and technical presentations made it clear that our
understanding of the observatory and its scientific capabilities was
markedly better than earlier this year. Both the GTO and Cycle 1 GO
programs have been completely revised; and a new catalog of
approved observations has been mailed to the community in advance
of the July 31/August 16 deadlines for Cycle 2 proposal submissions.

Despite the excellent work that has been reported and the new and
exciting observations to be taken over the next 2-3 years, the
presentations at the HST workshop reinforced the scientific
importance of restoring HST's performance at the earliest possible
opportunity. We are encouraged by the successful review of the
COSTAR design, a major milestone, and the continuing development
of the WF/PC replacement instrument. And we are grateful for the
recent resolutions of the AURA Board of Directors in this regard:

"The AURA Board of Directors commends the STScI staff and its
Director for initiatives taken in response to the problems
encountered in the HST mission. STScI has effectively represented
the interests of the astronomical community in maximizing scientific
returns with the current HST capability, in refashioning the
observing program, and in devising and advocating solutions to
restore the full HST capabilities.

"The AURA Board reaffirms the importance of effective STScI
involvement in decisions regarding the design, development,
calibration, and operation of the advanced scientific instruments for
HST. We encourage the STScI, because of its skills and experience, to
continue to engage the participation of the community in the
definition of the design and operation of future ultraviolet, optical,
and near-infrared observational facilities in space."

To begin the process of looking beyond the next three years and the
first maintenance mission, we intend to invite members of the
scientific community, spacecraft engineers, and representatives from
NASA to engage in a series of wide-ranging discussions on how best
to shape the long-term HST mission. Two new scientific instruments,
the Near Infrared Camera (NIC) and the Space Telescope Imaging
Spectrograph (STIS), are already being developed to replace some of
the existing instruments in 1997. But issues such as the need to
reboost the spacecraft before the next solar cycle and the need to
maintain adequate flexibility to respond to future problems are quite
complex. As for all difficult and worthwhile enterprises, we cannot
predict how these discussions will be resolved. But we are convinced
of their importance and the critical role that an informed and
involved scientific community must play in the life of HST.

-Peter Stockman & Riccardo Giacconi

HST Spacecraft Operational Status

On April 3, the HST pointing-control software was updated in an
attempt to counteract the jitter induced by thermal fluctuations in
the solar panels, which occur following terminator passages.
Although the software update has not eliminated the jitter, it has
substantially reduced the jitter amplitude (by about a factor of 2),
which in turn has significantly reduced the incidence of loss of guide-
star lock associated with terminator crossings. The remaining jitter
will produce some degradation of data taken during terminator
passage, and STScI is currently examining the seriousness of this on
an instrument-by-instrument basis. If it seems desirable, STScI will
propose changes to the ground system that would provide the option
of scheduling observations to avoid the periods when these
disruptions occur.

On May 2 at 14:43 (EDT) the HST spacecraft unexpectedly went into a
safemode condition governed by a special electronics assembly that
takes control whenever a serious defect is detected either in the
DF224 flight control computer or in the HST power systems. In this
condition, (known as "hardware sunpoint safemode") the telescope
aperture door is closed and the telescope and solar arrays are slewed
to place both perpendicular to the Sun. The scientific instruments
and other equipment were also placed into a safe low-power
configuration. The spacecraft properly executed all the steps
involved in reaching a safe configuration.

At the time of this event, HST was in a part of its orbit where it was
out of contact with the Tracking and Data Relay Satellite System
(TDRSS). Contact was re-established and analysis of the cause of the
safing began. Within a day it was evident that the most likely culprit
was memory unit #3 of the DF224, and plans were made to
reconfigure the computer to use one of the two spare memory units
in its place. The DF224 has a total of six memory units, of which four
are required for normal operations and two were onboard spares.

By the morning of May 5 the DF224 had been reconfigured,
diagnostic programs successfully executed, and the process of
safemode recovery begun. STScI prepared Science Mission
Specifications (SMSs) for the recovery of the scientific instruments
and to intercept the observing program on May 7. The recovery went
as planned and HST operations returned to normal. An investigation
into possible causes for the memory failure has begun.

-Rodger Doxsey


HST  Science HIGHlights

Special HST  Issue of Ap. J. Letters

The March 10, 1991, issue of Astrophysical Journal Letters was
devoted to a series of papers presenting the first scientific results
from HST. A total of thirteen papers discussed the imaging
performance of the telescope, and presented a wide variety of initial
results in solar-system, stellar, and extragalactic astronomy.



HST Results Presented at May Workshop

This year's STScI Workshop-"The Year of First Light"-was held at the
Institute on May 14-16. It was devoted to 29 presentations of the
latest scientific results from the HST mission and updates on the
spacecraft and instrument performance, and was attended by over
100 astronomers.

Several speakers emphasized that the spacecraft, telescope (aside
from the primary mirror's spherical aberration), and scientific
instruments are operating extremely well.

Space does not permit discussion of all of the scientific results here,
but among the highlights were the following:

n    WF/PC observations of Mars, Jupiter,
Saturn (during its recent storm event), and Titan

n    high-resolution imaging of the cores of two globular clusters

n    high-resolution spectroscopy of stellar-wind and
interstellar features in the spectra of galactic and
Magellanic Cloud hot stars, and of chromospheric and coronal
emission lines in cool stars

n    imaging and spectroscopy of circumstellar features
in R Aquarii, b Pictoris, h Carinae, and SN 1987A
n    imagery and spectroscopy of active galactic nuclei, jets,
and gravitational lenses
n    discovery of a low-redshift Lyman-alpha "forest" in
the UV spectrum of 3C 273


Thanks go to the Scientific Organizing Committee (Chris Blades,
Albert Boggess, Mike Fall, Riccardo Giacconi, David Leckrone, Colin
Norman, and Pete Stockman) for a most interesting workshop, which
demonstrated that a flood of exciting new science from HST is only
just beginning.

-Howard E. Bond



GHRS Observes chi Lupi

The remarkable power of HST's Goddard High Resolution
Spectrograph (GHRS) to provide entirely new information about the
compositions and physical properties of stars and other objects is
illustrated by observations of the chemically peculiar star c Lup,
obtained in February. This star is known from ground-based
observations to be rich in several normally rare chemical elements.
For example, its atmosphere contains 100,000 times more mercury
and 10,000 times more platinum per unit volume than does the Sun.
c Lup is a moderately hot star, with a surface temperature of about
11,000 K.

The GHRS spectrum was obtained in the echelle mode (resolving
power 87,000), through the Small Science Aperture, so that the
resolution was unaffected by the spherical aberration. The signal to
noise (S/N) ratio per data point in the continuum is about 100. The
first illustration, on the facing page, compares a section of the GHRS
spectrum with the corresponding section of the best previous
ultraviolet observation of c Lup, obtained with the International
Ultraviolet Explorer (IUE) satellite. The well-exposed IUE spectrum
has a S/N of approximately 15. The GHRS spectrum has 7 to 8 times
higher resolution than the IUE spectrum, and a S/N approximately 6
times greater. In principle the S/N of the IUE observation could be
improved up to a value of about 40 by co-addition of multiple
observations, but its resolution could not be improved beyond what
is shown here. Lines of several species are labelled in the GHRS
spectrum, but are barely detectable in the IUE spectrum.

The second illustration shows a 1.2 
 section of the GHRS spectrum of
c Lup. The strong line of Pt II near 1939.8 
 is in accord with the
known excess abundance of platinum in this star. Of special interest,
however, is the presence of two lines of UV multiplet 5 of Ru II,
believed to be the first identification of ionized ruthenium in a stellar
spectrum. The Ru II line strengths indicate an overabundance by a
factor of about 85 relative to the Sun.

-D. S. Leckrone


FGS ASTROMETRY: FIRST RESULTS

 The Early Release Observations (ERO) program has given the STScI
Fine Guidance Sensors (FGS) instrument team the first real
opportunity to gather data usable for assessing the scientific
potential of the FGS, given the telescope's spherical aberration. The
astrometric precisions reported below are worst-case estimates, since
Science Verification (SV) and Cycle 1 calibrations will substantially
improve our ability to retrieve scientific information from the FGS.

The FGS ERO observations consisted of a set of five consecutive
TRANS-mode scans of the binary ADS 11300 [= WDS 18230+1458
(2000)], obtained while  HST was held in Fine Lock (i.e., jitter less
than 10 mas). The length of the scans was approximately 1".2 with
an average sampling step of 0.6 mas. One of the y-axis scans is
shown in the first figure (dotted curve). Our low-order, piece-wise-
smooth polynomial least-squares fit to the data is also shown in the
figure (solid curve). One of the advantages of this particular
analytical representation of the data is that the subsequent
correlation analysis is performed analytically. The raw data consist of
a time series of photomultiplier counts and star-selector encoder
readings. These data must be transformed into the proper units and
corrected for instrumental and other effects before the curve shown
in the figure is obtained.

The reductions were performed in two steps. We first generated a
coarse grid of models with an 0.2 mag step size in magnitude
difference and a 10 mas step size in projected separation (on each
axis). The best-fit model in this grid provided us with the starting
values around which we generated a second, finer grid of double-star
models. Then a 0.05 mag step in magnitude difference and a 1 mas
separation step were used. Our final results are a separation of 52
mas along the x-axis and -44 mas in y. Given the geometry of the
scans, these projected separations imply a 68 mas separation on the
sky. The estimates of the magnitude difference were 0.45 and 0.3
mag along the two axes. The comparison between the observed and
best-fit model is shown in the second figure (again for the y axis).

A definitive error analysis is difficult in the present situation but
reasonable estimates can be made. By comparing the results obtained
using the five different scans, we estimate an internal error of 1 mas
for the separation. The external precision is impossible to evaluate at
present because of the lack of comparison values from planned SV
observations. However, some idea of this can be obtained by
intercomparing the results obtained with two very different sets of
models. It appears from this type of double-check that at least 5 mas
can be reached for the angular separation. The separation of the
binary, as predicted using the old (1975) orbital parameter set, is
about 50 mas but the error bars are large. The WDS catalog lists a
visual magnitude difference of 0.6 for ADS 11300. Considering pass-
band differences and the as yet unknown FGS photometric errors, it
is consistent with the value of 0.4 mag derived above (mean of the x
and y axes). A magnitude difference precision of 0.15 mag is
conservative.

-M. G. Lattanzi, B. Bucciarelli,

& L. G. Taff



HST Joint Discussion at IAU General Assembly

Astronomers attending the General Assembly of the International
Astronomical Union in Buenos Aires are invited to attend an all-day
Joint Discussion on HST results, to be held on July 31. The Scientific
Organizing Committee for this Joint Discussion is co-chaired by D.
Macchetto and C. Norman, and its members are H. E. Bond, A.
Boyarchuk, A. Davidsen, and G. Miley.



1992 EUROPEAN HST WORKSHOP

The ST-ECF and the STScI are planning a workshop to be held in
June1992 in Europe to discuss the scientific investigations possible
with HST in its early years, with a concentration on optimal
observing and data-analysis strategies. We hope to present results
from the first year of the General Observer program, prior to the
proposal deadline for Cycle 3. Details will be announced in the next
Newsletter.
-Ethan J. Schreier and Piero Benvenuti

List of HST Observations Grows

The last two issues of the Newsletter have contained detailed lists of
HST observations that have been completed or are scheduled to be
made in the near future. These lists have now grown too large (over
240 items each) for publication in the Newsletter. Anyone interested
in the telescope's activities can obtain the information from the Space
Telescope Electronic Information Service (STEIS) by downloading
files from the Observer subdirectories Completed_Observations and
Long_Range_Plan. (For instructions on using STEIS, see the December
1990 Newsletter.) If you do not have access to STEIS and would like
copies of these reports, contact the User Support Branch.
-Peter Reppert

Scientific INSTRUMENTS

Wide-Field and Planetary Camera

During the HST safing event on May 2, the WF/PC CCDs were at a
temperature of -35 C for about 80 hours, necessitating a
decontamination before observations could be resumed. The first
attempt at decontamination was unsuccessful, but a later attempt,
during which the CCDs were warmed above 10 C for about two hours,
resulted in the removal of all major contaminants. The UV flood was
conserved sufficiently that no quantum-efficiency hysteresis was
observed in a short test immediately after this episode. New flat
fields may be required at some wavelengths for some CCDs, however,
including PC8 in the blue and visible.

Observations were successfully executed for several programs of the
WF/PC GTOs over the past few months, including imaging of
interacting galaxies, gravitational lenses, and Jupiter. Some of the
early results were presented at the STScI May Workshop, as
described above, and one of the Jupiter images is shown in this issue.

The WF/PC Cycle 1 flat-fielding plan. As announced at the November
1990 GO Workshop, STScI plans to obtain and maintain flat-field
calibrations for the WF/PC (based on exposures of the Earth's
surface). The accompanying table gives the priorities for the Wide
Field (WFC) and Planetary Camera (PC) modes.

In addition to the filter-camera combinations listed in the table,
STScI will obtain flat-field exposures of the Earth with all filters used
by Cycle 1 GOs.

For the Priority 1, 2, and 3 flat fields, STScI plans to obtain exposures
at a variety of spacecraft roll angles and will create flat-field
calibration files for use in pipeline processing. The observations for
other filter-camera combinations will be made available (along with
STSDAS software and STScI consultants) to GOs needing flat fields for
those combinations. The pipeline calibration software to reprocess
the science observations is available in the current distribution of
STSDAS.

-Richard Griffiths & John MacKenty


WF/PC II

 At the instigation of the WF/PC II Science Team, JPL has started a
design study towards the possible inclusion of fold-mirror actuators,
in order to ensure alignment between the OTA pupils within the
WF/PC and the secondaries of the Cassegrain repeaters. The OTA
primary is re-imaged onto each of the eight WF/PC II repeater
secondaries, at which points the OTA spherical aberration is
corrected by the figures of the secondaries. A pupil/secondary
misalignment of 7% of the pupil diameter would lead to an rms
wavefront error equivalent to the current OTA problem, and an
alignment tolerance of 1% is required in order for the WF/PC II to
reach the minimum design goal of 60% encircled energy within 0".1
radius. Without the fold-mirror actuation, this specification might be
met in only one camera head.

Although the baseline design already includes actuation of the pick-
off mirror to allow for overall camera misalignment when installed
into HST, the Science Team has demonstrated that active adjustment
of the fold-mirrors will probably be necessary, because the repeater
secondaries are located at the ends of long moment arms. Fold-
mirror alignment tolerance at the level of 10", corresponding to 1
micron across the 2 cm-diameter fold-mirror, is necessary for the
goals to be met.

The WF/PC II CCD complement presently includes four of the original
TI three-phase devices, which have been judged to be flight worthy
and scientifically acceptable. Further TI devices are in the
qualification stages. As a back up for the rest of the needed devices,
however, JPL has contracted with CCD manufacturers for the
procurement of similar 8004800-pixel devices. Such devices
manufactured by Loral (formerly Ford Aerospace) have shown very
promising performance: read noise levels of 2-3 electrons rms and a
dynamic range of over 100,000, with stable performance and a
quantum efficiency at least as high as that of the TI devices.

-Richard Griffiths


Goddard High Resolution Spectrograph

GHRS observations have continued to progress well during its Science
Verification testing. Excellent spectra have been acquired for several
Cycle 0 GTO programs. With the exception of a carousel problem
described in detail below, which will have a significant but
temporary impact, the GHRS is performing nominally.

Target acquisition has seen much improvement, especially in the
initial pointing of HST for GHRS targets. All 28 stars observed
recently have been placed initially within a 343 spiral (1 2".75)
domain, with half being located at the first pointing

(1 1"). This suggests that 343 spiral searches are adequate if good
stellar coordinates are used. The automatic onboard acquisition
works well in terms of centering stars in the Large Science Aperture
(LSA). Placement of stars in the Small Science Aperture (SSA) is
currently done with blind offsets from the LSA. Two problems have
been encountered with proper centering of stars in the SSA: (1) for
very bright stars (the problem was first noted for

z Oph, V = 2.6) in the SSA, which does not have a shutter, scattered
light interferes with routine internal zero-point-deflection
calibrations (DEFCALs); and (2) the SSA PEAKUP step, which should
allow fine-tuning the object centering within the final aperture to be
used, failed to work properly. These problems prevent SSA
acquisitions from being as robust as with the LSA. Despite this, blind
offsetting to the SSA can be expected to succeed at the 80-90% level
(rough one-sigma estimate) relative to perfect centering.

The first quite red objects have recently been acquired by the GHRS.
Earlier experience, all with very blue objects, had shown responses
(relative to pre-launch expectation) for the four mirrors as follows:

N1 13%

N2 10%

A1 22%

A2 33%

Fortunately the response to red stars has been much closer to
nominal, implying the need for wavelength-dependent adjustments
to the mirror effective areas. Details have been posted in the Space
Telescope Electronic Information Service (STEIS), and were included
in a recent mailing to prospective Cycle 2 proposers.

An augmentation to GHRS target acquisition has been approved that
will allow a return to the brightest point of spiral search. (Currently
the process stops as soon as the BRIGHT and FAINT limits are
satisfied.) This is particularly important for acquisition of objects
with poorly known UV fluxes, such as variables, and should be
available for Cycle 2. Another augmentation will allow for better
centering of extended objects (to about 2" diameter) in the LSA.

All of the gratings have been measured for sensitivity over their full
spectral ranges. Losses relative to pre-launch expectations follow
from the geometric effect of spherical aberration, with the exception
of a further 20-30% loss over 1600-1900 
 with all gratings (this
discrepancy may result from errors in the ground calibration). The
explicit calibration tables were mailed to Cycle 1 GOs for support of
Phase II resubmissions, and more recently to Cycle 2 proposers.

It has been realized that the first-order gratings G160M and G200M
have contamination above 2200 
 from second-order light at half
the wavelength (e.g., Lyman-alpha appears at 2432 
). The G270M
grating has a blocking filter, and has second-order contamination
only above 3300 
. Full UV spectral coverage at intermediate
resolution (about 25,000) is still available without any contamination
with proper grating selection.

The recent determination (see the March 1991 Newsletter) that the
GHRS has greater sensitivity below 1500 
 than does the FOS leads
us to consider which of the two GHRS apertures is better for
detection of weak, unresolved spectral features in low-S/N data. For
equal exposure times, the LSA provides a S/N gain of a factor of two,
and a resolution loss of about a factor of two, relative to the SSA.
Detailed simulations (using PSFs of G140L including both OTA and
spectrograph contributions) have shown little difference between the
two apertures for detection of weak features. The LSA is probably
marginally better for isolated lines. If one also desires information
about the line profile, the simpler and sharper line-spread function
of the SSA is preferred. As count rates per diode fall to less than 0.02
per second in the SSA, the background noise of 0.008 counts per
second will degrade the relative S/N of SSA to LSA beyond the
canonical factor of two. In this event it is more likely that the LSA
will be preferred.

The issue of weak-line characterization in deconvolved LSA data has
also been explored. In terms of deriving equivalent widths, the
deconvolved LSA data perform worse than both direct PSF fits to raw
LSA data and SSA data. Therefore the deconvolution of LSA data is
not a benefit for this particular type of quantitative analysis.
Deconvolution of large-aperture data is useful for visualization
purposes, and may be of quantitative utility for some specialized
investigations.

-Ronald Gilliland



GHRS Observations of Interstellar Lines

GHRS data were successfully obtained on April 3 and 4 for two early-
type stars,     g 2 Velorum and HD 93521. Successful acquisition of g
2 Vel in the Small Science Aperture (SSA) was particularly welcome,
since the A1 mirror, necessarily used for this bright star (V = 1.8),
has not previously been very successful for target acquisition in this
aperture. For the fainter star (V = 7.0) the A2 mirror was used for
acquisition with success as usual.

These spectra were observed for a GTO program in collaboration with
C. R. O'Dell on ultraviolet interstellar absorption lines. As shown by
the GHRS team (Cardelli et al., Ap. J. Letters, in press), the GHRS
permits at least partial resolution of the absorption features
produced by different interstellar components, a technique
developed in previous decades by Hobbs and others at optical
wavelengths.

The figure on page 1 shows line profiles of several interstellar
species observed in g 2 Vel. The high counts per diode (at half-diode
intervals, thanks to the stepping pattern used) yield a S/N ratio
between 120 and 160; the presence of three interstellar components
is clearly indicated.

The high S/N ratio also permits a study of the fixed-pattern noise
(FPN), characteristic of the GHRS detectors. To help correct for FPN,
each exposure was split into three subexposures, with two successive
wavelength shifts of either 4 or 8 steps of the carousel encoder; the
corresponding velocity shifts are either 60 or 120 km s-1. A
preliminary analysis shows that for relatively smooth spectra the
scatter of photon counts can be significantly reduced by correcting
for the fixed-pattern noise. Thus in the S II region the observed
dispersion in each of the three normalized spectra can be reduced by
roughly half when divided by the FPN spectrum, determined by
combining the three subexposures; this correction should permit
photometric accuracies appreciably better than one percent. Also, the
data suggest that the FPN at each diode does not change much when
the echelle carousel is rotated by either 4 or 8 encoder steps, giving a
slight shift of the spectrum on the photocathode in a direction
perpendicular to the dispersion (as well as the much larger shift in
the parallel direction). However a rotation of 16 steps increases the
dispersion of the count differences between two subexposures by
some 15%.

-E. L. Fitzpatrick & L. Spitzer



Deconvolution of GHRS SSA Spectra

Deconvolution techniques are being developed for removing the
effects of the HST spherical aberration from GHRS spectra taken with
the Large Science Aperture (LSA), as described above and in a paper
that is in preparation.

A different sort of deconvolution is appropriate for spectra taken
with the Small Science Aperture (SSA), which are undersampled
because the aperture projects to only one detector diode.
Deconvolution is made possible by substepping the spectrum across
the detector in 1/4-diode steps, and then combining the four spectra
into an oversampled spectrum. Much to my surprise, the single test
case of SSA deconvolution that has been tried to date produced
rather stunning results. This approach was suggested a few years ago
by Ebbets and Lindler (Bull. AAS, 19, 747, 1987), and tested on
comparison-lamp observations. The discussion below is based on a
different technique (but other approaches will work as well), and is
applied to GHRS stellar data.

In this example, we deconvolve a spectrum of the peculiar star c
Lupi (see David Leckrone's article above). The star was observed at
intermediate resolution (R = 30,000) with the SSA, using the first-
order grating G160M with substepping of 4, and 4 FP-SPLITS,
yielding a mean signal-to-noise (S/N) per quarter-step of about 80.
For a "truth" comparison, c Lup was also observed with Ech-B (R =
90,000) through the SSA, but one of the FP-SPLITS was lost, resulting
also in a realized S/N of about 80.

The figure on the next page shows 10 
 sections (out of the 10.4 

coverage at this Echelle setting) of the original G160M/SSA spectrum,
the deconvolved G160M spectrum, and the high-resolution Echelle
spectrum. Realized resolving powers may be estimated by calculating
the FWHM of autocorrelation functions over the sharp-lined spectral
region between 1938.5 and 1939.5 
. This results in FWHMs of 3.42,
2.18, and 7.45 pixels, for formal resolving powers of 33,700 (G160M),
52,900 (deconvolved G160M), and 51,500 (Ech-B), respectively. The
Echelle spectrum does show some sharper lines than the deconvolved
G160M, suggesting that its calculated FWHM is biased upward by the
presence of some blended lines over the autocorrelation domain.

Deconvolution of the SSA data provides remarkably good results,
especially when it is noted that the exposure time for the Echelle
observation was a factor of 2.5 longer. Further, because the
wavelength coverage is greater by a factor of 3.3 for G160M, there
may be observing programs for which acquisition of first-order SSA
spectra, followed by deconvolution, will be preferable to Echelle
spectra. The first-order grating, G160M, can be used effectively to
below 1150 
, and is preferable to Ech-A on the basis of
photocathode cosmetics and scattered-light characteristics. In
principle the Echelle SSA spectrum could itself be deconvolved to
allow GHRS resolving powers well in excess of 100,000 to be reached,
although when this was done for the c Lup spectrum little
sharpening resulted, suggesting that the Echelle spectrum is already
starting to resolve the intrinsic stellar line profiles.

The combination of reduced exposure time (to reach the same S/N)
and increased wavelength coverage gives the first-order grating a
factor of 8.3 advantage. For projects in which full wavelength
coverage is a desired feature, but still at high (approximately 50,000)
resolving power, and high (approximately 100) S/N, use of first-
order spectra with factor of two wavelength redundancy (all
wavelengths covered twice) might be superior to Echelle
observations.

-Ronald Gilliland



GHRS Carousel Problem

The GHRS uses a carousel assembly with absolute encoders to
position dispersive elements and mirrors as needed for observations.
In recent weeks the carousel has failed intermittently to respond to
commands, leading to three GHRS safing events. Although the risk to
health and safety of the instrument from continued operation in this
mode is believed very small, the impact on telescope usage is
significant.

The carousel is driven currently by two independent sets of
electronics and motors, corresponding to the two detectors. Failures
have been a problem only for side 1 (the far-UV detector). The
carousel control electronics are fully cross-strapped, so that control
of the carousel may be effected from either set of electronics.
However, changing over to control of the carousel from only one side
involves substantial changes to flight software and ground
commanding, as well as the need for verification testing and
recalibration of some engineering-level relations. Efforts are now
underway at Ball Aerospace (prime contractor for the GHRS),
Goddard, and STScI to develop the required software changes as
quickly as possible. It is estimated that full implementation will
require some four to six months.

From recent experience, one may infer a roughly 50% failure
probability for observations using side 1. It has been decided that
use of side 1 will be deferred temporarily. Only programs using side
2 will continue to be implemented. Proposals that require side 1 (e.g.,
use of G140L or Echelle A, which have no effective side 2
replacements) will be held for now. An effort will be made to
identify Cycle 1 GO/GTO proposals that use side 1 in such a way that
switching to side 2 fully would not compromise the science return
(e.g., G140M use can often be replaced by G160M, and a target
acquisition with mirror N1 may well be feasible with mirror A2).

-Ronald Gilliland



High Speed Photometer

The High Speed Photometer continues to operate as expected. There
are no hardware problems. The throughput for the 1".0 apertures is
reduced by a factor of two below pre-launch expectation due to the
primary mirror's spherical aberration. There is no evidence for
decreased throughput (compared to pre-launch values) within the
HSP itself. The centering repeatability in the 1".0 apertures by
onboard acquisitions is about 0".02, and should not affect the quality
of the photometry. Currently, it is recommended that the 0".4
apertures not be used. Tests will be completed this summer that will
characterize the HSP performance in detail, especially the effects of
spacecraft jitter on photometry. As results are acquired they will be
summarized in the STScI Newsletter. More information        can be
obtained from Bob Bless (UWSAL:: bless, [e-mail]) or
Lisa E. Walter (SCIVAX::walter, [e-mail]).

-Bob Bless & Lisa E. Walter



FGS Science During Cycles     1 & 2

The recent completion of the Fine Guidance Sensor Early Release and
Science Assessment observing programs, when integrated with some
Orbital Verification data analysis, allows us to present an up-to-date
assessment of Cycle 1 FGS science. The bottom line is that FGS science
is largely unaffected by the primary-mirror aberration and the
secondary-mirror despace/tilt/decenter. The only significant effect
on the FGS will be a sensitivity loss of approximately one stellar
magnitude. In addition, the increased spacecraft jitter in Fine Lock,
even after removal, will contribute a 1-2 mas (rms) uncertainty in
positional data. In this article we will review the evidence for these
assertions, the current Cycle 1 calibration plans, and improvements
that can be made for Cycle 2. Because there are two very different
observing modes with the FGS, namely Transfer Function and
Position, we discuss them separately.

Transfer Function mode is primarily designed for multiple-star work
(this includes high-resolution "imaging" of more complex
astronomical scenes should the observational circumstances be
favorable). The astrophysical uses to which binary-star frequency
and orbits may be put are sundry. They range from classical mass
determinations to calibrate the mass-luminosity relationship-
especially for those astrophys- ically important double stars where
HST FGS observations can make meaningful measurements at orbital
phases where ground-based techniques cannot-to galactic-cluster
studies, which will help to understand problems such as mass
segregation, kinetic-energy equipartition, and star-formation
processes.

Transfer Function mode, after a deeper understanding of the
influences that govern the shape of the curve per se, was advertised
as being capable of measuring small angular diameters and
(relatively imprecisely) color indices. The former still seems feasible,
since the transfer functions for several of the FGSs have sharp
components comparable to the pre-launch simulations, though at
somewhat lower contrast when the full primary mirror aperture is
used. Measurement of color indices, however, seems improbable,
owing to the Optical Telescope Assembly (OTA) aberrations. We shall
discuss this in more depth below. Finally, Transfer Function mode is
ideally suited to projects such as a search for binary asteroids. The
data acquired for this purpose can be used simultaneously to
calibrate the minor-planet linear diameter/luminosity relationship
and to yield positional information that can be used to correct
differentially the orbital-element set.

The FGS ERO and SAO observations were all performed in Transfer
Function mode. Analysis of all the ERO and SAO data indicates that
Transfer Function mode, and transfer-function analysis, can support
the bulk of the pre-launch expectations, except that very close (<10
mas) or faint (D V > 3) companion stars will be difficult to detect with
confidence. The main difficulty is that the current OTA is producing
field-dependent aberrations in the fields of the FGS. Thus, to obtain
the maximum science from Transfer Function mode observing,
calibrations must be differential. For Cycle 1 only, STScI will plan
transfer-function calibrations in the FGS fields of view where GO
science targets were observed. Because of the small number of GO
programs using the Transfer Function mode, this technique will
garner the most science with the greatest efficiency in terms of HST
time.

Using this technique and correcting after the fact for spacecraft jitter,
one can measure binary separations to about 5 mas and magnitude
differences to about 0.1 mag. These accuracies will depend slightly
upon the magnitude difference between the two components and
their separation. A very faint secondary, also very close to its
primary (i.e., less than 30 mas), will not be so well resolved.
Conversely, a wide (> 50 mas) double is very easy to detect and
evaluate. The principal numerical problem is the relative
insensitivity of transfer-function analysis to the magnitude
difference. We found this to be true in our analyses of simulated data
and with real data, and are continuing to explore the reasons.

We feel comfortable that transfer-function analyses can work to a
magnitude difference of about 3 for secondaries brighter than 17th
mag. This is not very sensitive to the integrated brightness of the
binary. Improving these estimates (and possibly the performance)
will require better jitter-removal algorithms and the acquisition and
analysis of SV data; the FGS is still relatively uncalibrated. The
recommended telemetry rate for all FGS observations is 32 kbs, and
in this mode, when the guide stars are in Fine Lock, there is the
potential for a nearly complete removal of the spacecraft motions
about the line of sight. Thus we anticipate better performance for
future observing cycles.

Additional Transfer Function calibrations during Cycle 1 will explore
the OTA-induced field dependence and evaluate the true potential
for angular-diameter measurements. While angular-diameter
observations may not be calibrated properly before Cycle 2, their
importance for independent measurements of nearby stars and
minor planets is clear.

Position mode is primarily designed for single-star work, in
particular the precise determination of positions of stars brighter
than V = 17. The astrophysical uses to which high-precision positions
may be put are varied, and include parallax determinations for zero-
age main-sequence stars, the calibration of the Cepheid period-
luminosity relation, luminosity calibrations for various stellar classes,
stellar kinematics, studies of open clusters (wherein HST will allow
work on much fainter objects than can be reached from the ground
or from HIPPARCOS), and measurement of nebular expansion rates.

Although there have been no scientific observations attempted in
Position mode, there is information regarding its potential precision.
The analysis of FGS calibration data obtained to improve HST
pointing has revealed previously unknown color-index and
magnitude effects in the ground-based reference catalog. The
discovery of these small (approximately 10 mas) biases in the
ground-based data makes us very optimistic regarding even higher
precisions with the FGS Position mode, in the near future. We believe
that our original expectation of 5 mas for a single FGS positional
observation will be met, following the successful calibration of the
field distortions and the absolute plate scale. For parallax work, this
performance implies a 2 mas precision in the deduced annual
parallax when 10 reference stars are utilized over multiple observing
opportunities. This value comes from the usual propagation-of-error
formulae and does not include any hidden, milliarcsecond-level
systematic effects. To optimize the calibration of the Position mode,
which is extremely complex and time consuming, STScI will integrate
much of the Cycle 1 calibrations with the formal science calibration
program of the Astrometry Science Team. The two groups intend to
analyze the calibration data independently. Improved estimates of
the Position-mode performance will be reported in future
Newsletters.

-M. G. Lattanzi & L. G. Taff


PROPOSAL NEWS

Revision of GTO Award due to Spherical Aberration

After the full scientific impact of the HST spherical aberration was
understood, NASA re-evaluated the observing-time award structure
for the Guaranteed Time Observers (GTOs). In general, many of the
originally proposed scientific programs of the GTOs could still be
accomplished, but with a significant amount of increased exposure
time. Recognizing that major increases in GTO time would directly
affect access to HST by General Observers (GOs), NASA worked
directly with various advisory groups to ensure that a new policy on
GTO awards was developed that was as fair as possible to both GTOs
and GOs.

After many months of discussion with the HST Science Working
Group (SWG), the Space Telescope Institute Council (STIC), the Space
Telescope Advisory Committee (STAC), and the Space Telescope
User's Committee (STUC), NASA issued a policy statement on GTO
observing time that was acceptable to the GTOs and to the GOs as
represented by the STIC and STScI. The main points of this policy are
detailed below:

1.    GTOs may assign their observing     time         to any pre-
maintenance-mission Cycle         and specify which programs
would be         deferred to the post-maintenance-mis-        sion
era.

2.    The GTO observing program must be         completed within
a period defined by the         end of Science Verification plus 5
years,         or within 2 years after the maintenance
    mission (whichever is later).

3.    Deferred GTO programs will not be pro-        tected. A GO may
propose the same sci-        ence on the same target, but must fully
        justify why such a program should be         done in the
pre-maintenance-mission         era.

4.    The baseline GTO observing time pro-        gram is 2450 on-
target hours (the same         amount of time as prescribed by
previous         policies). On-target time means the pe-        riod
of time from the initiation of tele-        scope guidance procedures
(e.g., fine         lock, coarse track, etc.) to the end of a         given
observation (e.g., shutter closure).

5.    Each GTO team may propose for addi-        tional time
(above their baseline), not to         exceed a total of 3 calendar
months for         all the GTOs combined.

6.    These proposals will be peer reviewed by         the same
Time Allocation Committee         (TAC) that evaluates GO proposals
for         Cycle 2. The TAC will review all GTO
    augmentation observing-time requests         and make a
recommendation to the HST         Program Scientist, who has
the             responsibililty to make the final award
    decisions (after consultation with the         STScI Director).

7. In order to ensure fair access to HST ob-        serving time by
GOs, another constraint         was added to the policy. The total
            amount of GTO observing time will not
    exceed 30% of the time assigned to sci-        entific
observations averaged over the         period of GTO observations.
In addition,         after the WF/PC II is operating, the total
        GTO plus WF/PC II science team share         of the
observatory may not exceed 40%         in any given year.

Although the terms of this policy provide the possibility of awarding
additional observing time to the GTOs, the amount of additional time
in no way restores the ability of the GTOs to accomplish their
originally proposed science programs. To accomplish that goal would
require an inordinate amount of extra observing time that would
severely impact access to HST by the GOs. This policy is the result of
much negotiation among many scientists and it is probably the best
compromise that could be reached given the situation.

-Edward J. Weiler



Status of Science Programs for Cycles 0 and 1

The GTOs and GOs have recently completed the revisions of their
current and Cycle 1 science programs. After a painstaking and time-
consuming process, the observational strategies of existing GTO and
GO programs were either suitably modified, or the programs were
withdrawn or deferred to a time when the HST optical aberration has
been corrected. The policies that have been adopted for GTO
programs are described in the preceding article, and the following
article discusses the recent GO reassessment in detail.

This replanning effort has yielded a reconstructed science program
that is nearly finished for Cycle 0 and is about to begin in earnest for
observations scheduled for Cycle 1. Cycle 1 nominally begins on July
1, 1991, and will last 12 months.

For those interested, several kinds of information for specific GTO
and GO science programs (e.g., abstracts, target and exposure
information, tentative schedule, etc.) can be obtained directly from
STEIS, as well as this and future Newsletters.

-Bruce Gillespie



The Cycle 1 GO Reassessment

The Reassessment Time Allocation Committee (TAC) met at STScI
during February 25-27 to reevaluate the initial Cycle 1 General
Observer (GO) program in light of the current HST capabilities. The
Director's review of the TAC's recommendations took place in early
March, and the PIs were notified of the results by mid-March.

Members of the TAC were selected from the original Cycle 1 TAC and
subdiscipline panels. The membership of the Reassessment TAC is
given in the accompanying table.

The task of the Reassessment TAC was to determine the continuing
scientific viability and merit of all of the GO programs that were
approved in 1989 for the first cycle of HST observations. The policies
related to this exercise were summarized in the December 1990
Newsletter. The reassessment was carried out in order to optimize
the scientific return from HST during its initial period of impaired
operation with the spherically aberrated telescope optics. Since it
would have been impractical to reconstruct completely the first
year's science program at this time, it was decided to use the GO
allocations for Cycle 1, which were made before the optical problem
was known, as the basis for a revised program. Only those
observations that were allocated to Cycle 1 were reviewed; future
cycles were not considered during this reassessment.

It was not possible to retain all of the original GO observations that
remain feasible in principle because the required increases in their
spacecraft time or their deferment until the installation of second-
generation instruments could easily have consumed most of the
available time for the next several years and precluded any new
allocations for the foreseeable future.  The fundamental intent has
been to favor programs with greater scientific potential relative to
the current state of HST, rather than pursuing heroic efforts for
marginal results from proposals designed for the ideal telescope.

The final approved list of high-priority GO Cycle 1 programs is given
on the next four pages, where programs are ordered by Scientific
Category. Listed are the PI's surname, country, institution, and
program title.

We present below a box giving a few statistics related to the GO Cycle
1 reassessment.  Other notes and statistics were given in the March
1991 Newsletter.

-Kirk D. Borne



Cycle 2 Proposal Information

The deadline for HST Cycle 2 proposals was recently announced in a
special mailing to individuals and institutions on our mailing list.
Highlights of the announcement are as follows:

1. The deadline for receipt of all materials at STScI for Cycle 2 Phase
I proposals is August 16, 1991 (5 pm EDT). This deadline applies to
proposals submitted in "electronic-plus-paper" form, which is
required for all proposers who have access to U.S. electronic mail. For
those who have no electronic access, "paper-only" proposals are
permissible but must be submitted earlier, with a deadline of July
31, 1991 (5 pm EDT). Please note that the "electronic" Phase I
proposal mechanism is described in the May 1990 Phase I Proposal
Instructions, and is not the same as the Phase II (RPSS) system used
by successful proposers after selection. RPSS-generated proposals
will not be accepted for Phase I submissions.

2. The documents issued to the community in May 1990 with the
Cycle 2 Call for Proposals contain instructions, forms, and pre-launch
technical information. This information should be consulted by all
astronomers considering proposal submissions for Cycle 2. These
documents should be available in astronomy libraries, but copies can
be provided upon written request to the User Support Branch.

3. There have been significant changes in the proposal instructions
since May 1990 that will make proposing easier for many
astronomers, and considerably revised technical information
regarding current instrument and spacecraft performance is
available. The recent mailing described these changes and revisions.
Where practical, we have also posted this information on STEIS. Since
additional clarifications and corrections to the Cycle 2 Call for
Proposals will be posted in STEIS, we encourage proposers to check
STEIS regularly (especially the "Cycle_2_updates" subdirectory under
the "Proposer" directory.)

The date for the Cycle 2 TAC meeting has not been determined at
this time, but is most likely to be in mid-November. Selection
notifications to Cycle 2 proposers should be mailed within a few
weeks after the TAC meetings, and successful GOs will be given
instructions on submitting their Phase II programs, which will be
due roughly two months later. The Cycle 2 observing program will
commence on July 1, 1992. In order to maintain the yearly schedule,
we plan a complete revision of our user documentation and issuance
of the Cycle 3 Call for Proposals early in 1992, with a proposal
deadline tentatively set for July 1992.

-Bruce Gillespie



Director's Discretionary Programs

As pointed out in the Cycle 2 Call for Proposals, it is possible for
observers to be allocated HST observing time outside of the normal
TAC procedures, through the Director's Discretionary (DD) program. A
request for DD time might be appropriate in cases where a truly
unexpected transient phenomenon occurs, when developments since
the last proposal cycle make a time-critical observation necessary, or
when it is desired to use HST and its instruments in an innovative
way.

The HST observing schedule is determined several months in
advance of the actual observations. Although it is technically feasible
to interrupt the schedule and initiate observations of a new target
within 48 hours, such short-notice interruptions place very severe
demands on the HST planning and scheduling process. Interruptions
of this sort are limited to one per month. For these reasons, requests
for DD time must be extremely well justified, and, if at all possible,
submitted at least three months before the date of the requested
observations. In view of the long lead times, it will in most cases be
more appropriate to submit a proposal through the normal GO
procedures (as a Target of Opportunity program) than to request DD
time.

As noted in the Call for Proposals, DD requests should be submitted
on the standard Cycle 2 forms to the User Support Branch, using the
standard "paper-plus-electronic" (or, if necessary, the "paper-only")
procedures. Item 3 on the Cover Page should indicate that the
request is for "DD" time. In addition, the paper portion of the
submission should include a cover letter describing the need for DD
time.

The DD programs that have been accepted to date are listed in the
accompanying table. The first three were submitted between the
original Cycle 1 TAC meeting and the recent TAC reassessment, and
were reviewed for scientific merit during the second TAC meeting.
Five additional DD requests were not accepted.

-Howard E. Bond



SOFTWARE NEWS

STSDAS News

The next major release of the Space Telescope Science Data Analysis
Software (STSDAS), Version 1.2, will be coordinated with the next
release of IRAF, Version 2.10. A final date for this release has not yet
been established, but our current estimate is for late summer or
early fall. Sites interested in staying up to date need not wait for the
next major release, however. STEIS contains patch kits for STSDAS,
and users may simply retrieve and install these kits in order to have
a current version of the system. The kits are located in the directory
Software/Stsdas/V1.1/Bugfixes and are called patch1.tar, patch2.tar,
and patch3.tar. Please review the README file for the complete
installation instructions. The third patch kit includes new tasks for
image restoration: a Wiener filter program and a task to run the Lucy
algorithm. Note: the patch kits must be installed sequentially.

- Bob Hanisch



Image Restoration Workshop Proceedings

The proceedings of the Workshop on HST Image Restoration held at
STScI in August 1990 have been published, and over 900 copies
have been distributed. Our supply has been exhausted, so if you did
not get one please check your local astronomy library for a copy. The
volume is entitled "The Restoration of HST Images and Spectra," and
was edited by R. L. White and R. J. Allen.

- Bob Hanisch



Telescope Image Modelling Software

The Telescope Imaging Modelling (TIM) software (see the December
1988 STScI Newsletter and the May 1990 Optical Telescope
Assembly Handbook) was developed at STScI to simulate images
produced by HST and its scientific instruments. New features have
been added to TIM recently. In particular, a new program has been
provided to write appropriate input files for WF/PC obscurations at
specified field positions. The TIM User Manual has been revised to
document these enhancements. Release 25 of the software, along
with the applicable User Manual (version 7), is now available to the
general user community. In addition to the User Manual a Beginner's
Guide and TIM Cookbook have also been provided with this release.

The software is available to GOs and others to use at STScI, where it
is installed on SCIVAX in the directory DISK$KRYPTON:[HASAN.SYS].
User guides may be requested from the User Support Branch. Offsite
users may retrieve it from the STScI Electronic Information Service
(STEIS) via ftp to a local VAX computer. VMS backup tapes may be
requested from the User Support Branch by those users who do not
have access to SCIVAX or STEIS.

The process for retrieving TIM, relevant portions of the package,
XCAL (a synthetic photometry package developed by Keith Horne),
and the Calibration Data Base System (CDBS), used by TIM, is the
same as described in the December 1990 STScI Newsletter. The
README file in the STEIS directory Software/TIM describes the
software and instructions for copying it to your local VAX computer.
The savesets tim25.bck, xcal25.bck, cdbs25.bck may be unpacked by
running the file backup.com in the Software/Tim directory. If you
have questions please contact Hashima Hasan at STScI (301-338-
4519; userid HASAN).

-Hashima Hasan



Data Retrieval from the  HST Archives

As a step along the way to making the HST archives generally
available to the community over computer networks, we intend to
provide access on an experimental basis to the catalog of
observations which is accumulating on our interim archive machine,
the Data Management Facility (DMF).

The DMF catalog can be queried with the software tool STARCAT,
which permits browsing of the catalog and compilation of lists of data
sets that may later be retrieved upon request. Interested users
should contact the User Support Branch (800-544-8125; userid USB)
for information on STARCAT, and instructions for running it on our
"stsci" computer using "telnet." We will also be interested in
comments on STARCAT as we design the user interface software for
DADS, the final  HST archive system.

The utility of STARCAT is unfortunately limited by the fact that
many of the keywords for old data in the catalog are presently not
correct. This problem will be fixed by re-processing the old data, an
activity that is currently planned to start at the end of the summer.

STARCAT searches that fail because of keyword errors can be run
successfully with the help of additional information about completed
observations, which is available on STEIS in the
Observer/Completed_Observations directory.

In order to request retrieval of data from DMF, one must know the
root names of the HST data sets. STARCAT can provide these, as well
as information about the proprietary status of the data. The
subsequent steps to follow in order to request retrieval of data from
DMF, as well as the telephone number of the "archive hotline" to call
in case of difficulty, are described in the information available from
USB.

-Ron Allen



AURA NEWS

AURA Welcomes New Board Members

The Association of Universities for Research in Astronomy (AURA) is
pleased to welcome the following new institutional members on its
Board of Directors: Michael A'Hearn (University of Maryland), Hollis
Johnson (Indiana University), Edward Kibblewhite (University of
Chicago), and Paul Schechter (MIT). In addition, Carole Jordan (Oxford
University) has been elected as a new AURA Director-at-large.

Our thanks is extended to departing Board members: Robert Dorfman
(University of Maryland), Kent Honeycutt (Indiana University),
Stuart Rice (University of Chicago), George Clark (MIT), and William
Golden.

-Lorraine Reams



1991 AURA Awards

In 1990, AURA began its program of presenting two awards each at
STScI and at NOAO to individuals who have made outstanding
contributions in the area of science or service. On February 11, AURA
presented its awards to the STScI recipients listed below. Each
awardee received a certificate and cash award.

Christopher Burrows received the AURA award for outstanding
service, in recognition of his initiative and outstanding performance
in the analysis of spherical aberration in the HST Optical Telescope
Assembly (OTA). By comparing simulated images to the earliest
WF/PC data received from HST, he was the first analyst to discover
the existence and degree of spherical aberration in the HST OTA.

Abhijit Saha received the AURA award for outstanding science in
recognition of his observations of RR Lyrae stars in the distant
galactic halo and the Local Group of galaxies. The periods and light
curves of RR Lyrae variables have been used to estimate the
distances and chemical composition of nearby and distant stars in
our own and external galaxies.

-Lorraine Reams



HUBBLE FELLOWSHIP PROGRAM

eleven New Hubble Fellows Appointed

The selection process for the second year of the Hubble Fellowship
Program has been completed. The awardees, selected from a pool of
115 highly qualified candidates from 24 countries, and their Host
Institutions, are listed in the accompanying table. Their
appointments will commence in the fall of 1991.



The 1992 Hubble Fellowship Program

Contingent on funding from NASA, up to 12 new Hubble Fellows will
be selected this winter for terms beginning in the fall of 1992. A
formal Announcement of Opportunity will be issued in mid-July
1991, and the application deadline will be November 15, 1991.

The main objective of the program is to provide recent postdoctoral
scientists of unusual promise and ability with opportunities for
carrying out HST-related research. A qualifying Host Institution must
be a scientific, non-profit U.S. organization where HST-related science
can be carried out successfully. Applications will be accepted from
candidates of all nationalities who have earned their doctorates after
January 1, 1989, in Astronomy, Physics, and related disciplines.

The duration of a Fellowship is a total of three years, which includes
an initial period of two years and an extension of another year,
which is granted after a positive mid-term review.

The detailed Announcement of Opportunity, including the
Application Instructions, is available upon request from the Hubble
Fellowship Program Office at STScI (userid HFELLOWS).

-Nino Panagia



INSTITUTE NEWS

PASP COMES TO STScI

On May 1, the editorial offices of the Publications of the Astronomical
Society of the Pacific (PASP) were relocated to STScI. For 23 years
the PASP was edited by D. Harold McNamara (Brigham Young
University), to whom the ASP and the astronomical community owe a
vote of thanks for his dedicated service.

The new Managing Editor of PASP is Howard E. Bond. He is assisted at
STScI by Deputy Editor Abhijit Saha and Editorial Assistant Denise
Dankert. Lloyd Robinson (Lick Observatory) continues as Associate
Editor for Instrumentation and Software.

The PASP continues to welcome manuscript submissions in all areas
of astronomy, including papers describing instrumentation and
software. Contributions reporting HST results, of course, are
particularly welcome!

-Howard E. Bond



SABBATICAL & LONG-TERM VISITORS AT STScI

In order to promote exchange of ideas and collaborations in HST-
related science, STScI expects to provide limited funds to support
visiting scientists who wish to spend extended periods of time (three
to twelve months), typically on sabbatical leave from their home
institutions or during the summer, doing research at STScI.

In general, these visitors will have the status of STScI employees and
have access to the facilities available to staff members.

Established scientists who might be interested in such a visit during
the summer of 1992 or during the academic year commencing in
September 1992 should send a letter specifying the suggested period
for the visit and other relevant details to the Visiting Scientist
Program, c/o Tim Heckman (301-338-4442; userid HECKMAN), at
STScI. It will be helpful if candidates include a recent curriculum
vitae and a short description of their research plans.

-Tim Heckman



STScI MINI-WORKSHOPS

STScI's program of specialized "mini-workshops" continues to be
active. The following mini-workshops will be held at STScI in the
coming months.

A mini-workshop on "The Reion- ization of the Intergalactic Medium"
is being organized by Piero Madau and Avery Meiksin, and will be
held at STScI August 19-20, 1991. The primary goal of the meeting
will be to discuss the current understanding of the state of the IGM,
both its diffuse and clumped components, in an informal atmosphere.
The schedule will be divided into four half-day sessions addressing
both theory and observations. Specific topics include, but are not
restricted to: the H and He Gunn-Peterson test; the UV metagalactic
flux-constraints from the proximity effect and the ionization of metal
systems; sources of photoionization-QSOs, AGNs, young galaxies;
quasar absorption systems-HST observations at low z; and the hot
IGM.

A mini-workshop on "Active Galactic Nuclei" will be held August 21-
23, 1991, and will be devoted to AGNs at high redshifts. The primary
goal of this workshop is to understand better the cosmic evolution of
the AGN population by both statistical analyses of the properties of
AGNs as a function of redshift and by detailed analyses of the
environments of individual high-redshift AGNs. This workshop is
being organized by Anuradha Koratkar.

A mini-workshop on "Nonisotropic and Variable Outflows from Stars"
will be held October 8-10, 1991. This workshop, organized by
Laurent Drissen, Claus Leitherer, and Antonella Nota, will bring
together about 50 people to discuss the properties of outflows from
pre-main sequence stars, as well as OB, Be, and Wolf-Rayet stars,
luminous blue variables, symbiotic stars, and supernovae. The
workshop talks and posters will be published in the Astronomical
Society of the Pacific Conference Series.

Because of limited space, attendance at the mini-workshops is by
invitation only. Interested scientists should contact any member of
the organizing committees for further information.



STScI SUPPORT FOR PRESS RELEASES

If you believe your HST research results are newsworthy and of
interest to the general public, you are encouraged to disseminate
such information to the public through a press release. As a GO, it is
your prerogative to release exclusively from your home institution,
to co-release with STScI, or to release exclusively via STScI's
Educational and Public Affairs (EPA) office.

STScI offers many services to assist you in announcing new science
results to the public. EPA has a positive working relationship with
reporters, science journalists and TV news media around the world.
In addition to printed releases with color prints, EPA can prepare
video news releases in our Astronomy Visualization Laboratory
utilizing computer-graphics techniques. HST scientific results are also
incorporated into our quarterly educational newsletter Observer,
NASA-Select TV programming, our weekly PBS TV series
"Starfinder," and educational posters and slides. In the event of a
major scientific discovery, STScI has the facilities in place to televise
a news conference from the STScI auditorium, via NASA-Select TV.

-Eric Chaisson



STEIS Update

The online Space Telescope Electronic Information Service (STEIS)
has several new features. There is a new Long_Range_Plan
subdirectory, which contains a tentative HST observing schedule for
a period of at least the next six months. Observations needing real-
time interactions are noted in the plan. A new weekly summary file,
week_summ_date, has been added to the Observer/
Completed_Observations directory.

Several other new directories have also been added:
"Instrument_News," which contains updates on performance of the
scientific instruments; "Policy," which contains copies of recent
mailings to observers and proposers, formerly scattered throughout
the directory tree; and "Proposer/Cycle_2_updates," which contains
information on proposal submission. As discussed separately above, a
new version of the TIM software has been posted. This includes the
cdbs and xcal backup files and all of their complementary files.

"Starcat" and "PASP" are new top-level directories. Starcat was
created to assist Archival Researchers who use STARCAT to search
the archive data base. The resulting output file containing lists of
selected archive data files will appear in this directory and can then
be downloaded (using anonymous ftp) to the user's home computer
for use in preparing the archival data request. PASP will contain
information useful to readers of the Publications of the Astronomical
Society of the Pacific, whose editorial office is now located at STScI as
reported above.

To keep up with the latest new postings to STEIS, be sure to read the
new_items file in the main directory. An electronic copy of each
STScI Newsletter is available from the Stsci/Newsletters directory.

-Pete Reppert and Chris O'Dea



RECENT STScI PREPRINTS

The following papers have appeared recently in the STScI Preprint
Series. Copies may be requested from Sharon Toolan (301-338-4898;
userid TOOLAN) at STScI. Please specify the preprint number when
making a request.

525. "W28 and 3C 400.2: Two Shell-Like Radio X-Ray Morphologies,"
K S. Long, W.P. Blair, R.L. White, and Y. Matsui.

526. "Ring Nebulae around Wolf-Rayet Stars in M33," L. Drissen, M.M.
Shara, and A.F.J. Moffat.

527. "Infrared Photometry of Compact Objects in the Magellanic
Clouds," F.P. Israel and J. Koornneef.

528. "What Determines the Physical Quantities of Galaxies? A Two-
Component Gas Model for Protogalaxies with Energy Input from
Supernovae," S. Ikeuchi and C.A. Norman.

529. "The Study of Lithium in Stars like the Sun," D.R. Soderblom.

530. "The Featureless Continua and Hydrogen Lines of Seyfert 2
Galaxies," A.L. Kinney, R.R.J. Antonucci, M.J. Ward, A.S. Wilson, and M.
Whittle.

531. "Relic Cosmological H II Regions and the Origin of the Lyman-
alpha Forest," A. Meiksin and P. Madau.

532. "Observations of Stellar Winds from Hot Stars at 1.3 mm," C.
Leitherer and C. Robert.

533. "Eclipse Studies of the Dwarf Nova HT Cas. I. Observations and
System Parameters," K. Horne, J.H. Wood, and R.F. Steining.

534. "A Non-Deterministic Approach to Schmidt-Plate Astrometry,"
M.G. Lattanzi and B. Bucciarelli.

535. "Memberships and CM Diagrams of Young Open Clusters. I. NGC
225," M.G. Lattanzi, G. Massone, and U. Munari.

536. "In-Flight Performance of the Faint Object Camera of the Hubble
Space Telescope," P. Greenfield, F. Paresce, D. Baxter, P. Hodge, R.
Hook, P. Jakobsen, R. Jedrzejewski, A. Nota, W.B. Sparks, N. Towers, R.
Laurance, and F. Macchetto.

537. "Cataclysmic-Variable Evolution: Clues from the Underlying
White Dwarf," E.M. Sion.

538. "The Dark-Matter Content of Spiral Galaxies," P. Salucci, K.M.
Ashman, and M. Persic.

539. "Radiatively and Shock-Excited H2 in Magellanic H II Regions,"
F.P. Israel and J. Koornneef.

540. "What are the GHz-Peaked-Spectrum Radio Sources?," C.P. O'Dea,
S.A. Baum, and C. Stanghellini.

541. "Weighted Slit Extraction of Low-Dispersion IUE Spectral Data,"
A.L. Kinney, R Bohlin, and J.D. Neill.

542. "Studies of Dynamical Properties of Globular Clusters. VI. The
High-Concentration Cluster NGC 6397," G. Meylan and M. Major.

543. "Rotation and Emission Lines in Stars and Accretion Disks," K.
Horne and S.H. Saar.

544. "Interstellar Ca II in the Galactic Halo and in QSO Absorption
Systems," D.V. Bowen.

545. "Massive Star Formation and Superwinds in IRAS 19254-7245
(The TSuper Antennae')," L. Colina, S. Lipari, and F. Macchetto.

546. "An Optical Study of 3C 31, 3C 66B, 3C 120, and their Jets," D.
Fraix-Burnet, D. Golombek, F.D. Macchetto, and J.-L. Nieto.

547. "Echo Images of AGN Broad-Line Regions," W.F. Welsh and K.
Horne.



HOW TO CONTACT STScI

Telephone: If an individual staff member's extension is not known,
the number for general use is 301-338-4700.

Telex: 6849101-STSCI

Fax: [phone]

Mail:     STScI

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E-mail: It is possible to reach most staff members at STScI on SPAN,
Bitnet, and Internet. Address formats are as follows:

SPAN:    SCIVAX::userid

            or 6559::userid

Bitnet:    [e-mail]

Internet:    [e-mail]

In most, but not all, cases the userid is the staff member's last name.
Alternatively, many userids are published in the Membership
Directory of the American Astronomical Society. If you have
difficulty reaching someone, 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.



ESA FELLOWSHIPS AT STScI

Astronomers of European Space Agency (ESA) member countries are
reminded of the possibility of coming to STScI as ESA Fellows.
Prospective fellowship candidates should aim to work with a
particular member or members of the ESA staff at STScI, and for this
reason applications must be accompanied by a supporting letter from
STScI.

Details of the interests of staff members at STScI can be obtained
from Dr. J. E. Pringle in the Academic Affairs Division (301-338-
4477, userid PRINGLE). Details of the fellowships and application
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 March 31 for consideration in May,
and no later than September 30 for consideration in November.



Newsletter Notes

Comments on the STScI Newsletter should be addressed to the Editor,
Howard E. Bond (301-338-4718; userid BOND). Mailing-list
corrections should be sent to Amy Connor (userid CONNOR).

Persons who assisted in the preparation of this issue include John
Godfrey, Dave Paradise, Pete Reppert, and Meg Urry.

The STScI Newsletter is issued three to four times a year by the
Space Telescope Science Institute, which is operated by the
Association of Universities for Research in Astronomy, Inc., for the
National Aeronautics and Space Administration.