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Space Telescope Imaging Spectrograph
STAN - June 1998

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STScI                        .  . __..___.                       Number 8 
Analysis                     |__|(__   |                         MAY 1998
Newsletter                   |  |.__)  |   
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               G H R S     ( S | T | I | S )      F O S  
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CONTENTS:
 
	- STIS CALIBRATION NEWS 
	  + echelle, first order M mode and imaging throughputs derived.
	  + improved echelle traces, first order mode distortion 
	        correction, and CCD spectral flats under construction.

	- STIS PIPELINE and SOFTWARE
	  + new version of calstis (1.8) available for downloading,
		includes many fixes and enhancements. Do get it!
	  + includes tasks for target acq analysis, daily darks, 	
		fringe flats.

	- ANALYSIS NOTES
	  + cosmic ray rejection can go awry for filtered imaging modes
	  + making fringe flats for your G750L and G750M data.
	  + recalibration of echelle data taken from February to May 98

	- REFERENCE FILE NEWS
	  + new echelle, M mode throughputs, PCT tables
		Many updates imminent - heads up.

	- OBSERVING PLANNING
	  + getting your target coordinates right
	  + etc updates
	  + new STIS Instrument Handbook coming soon.

        - NEW STIS DOCUMENTATION 
          + STIS ISRs (Instrument Science Reports), FAQs, and Advisories.

        - GHRS NEWS
	  + update to the diode response file

        - FOS NEWS     
	  + ALL Spectropolarmetry Data Recalibrated and Rearchived!!!

        - DATA ANALYST POSITIONS AVAILABLE AT STScI

        - RECENT PREPRINTS 
 
        - APPENDIX: HST Spectroscopy Contacts
	
============================================================================ 

			STIS CALIBRATION NEWS
                        ---------------------

+ Echelle on orbit sensitivity calibration complete.

Point source sensitivity curves for the 0.2x0.2 arcsec entrance aperture were
derived for the echelle medium and high dispersion modes (E140M, E140H, 
E230M, E230H) which collectively span a wavelength range from 1140 to 3150 
Angstroms. The new curves have been delivered to the calibration 
pipeline (see Pipeline and Software News below). The sensitivity for each 
order was determined by comparing observations of spectrophotometric standard 
stars with their standard star flux distributions. In general, the 
uncertainty in the calibration is roughly +-5% two-sigma. There are a few 
isolated wavelength regions where line blanketing in the calibration star 
used was particularly extreme; for example for E140H-1234 at the short 
wavelengths, the uncertainty can reach +-25%, even for the relative flux 
within one order. The details will be described in a forthcoming STIS 
ISR (Bohlin, 1998).

+ First Order Mode Medium Resolution Sensitivity Calibration Complete.

Point source sensitivity curves for the complete set of medium resolution
first order mode central wavelengths (G140M, G230M, G230MB, G430M, and G750M)
have been derived with accuracies of +-4% two sigma for the prime settings
and delivered to the pipeline (see below). Details will be provided in 
a forthcoming STIS ISR (Keyes, 1998).

+ On Orbit Calibration Checks of CCD and MAMA Imaging Modes Performed.

The imaging mode throughputs have been analyzed based on
on-orbit calibrations. As of 5/21/98 this is an
interim calibration and is expected to be updated within
the next month. Changes are less than 15% relative to the 
pre-launch throughputs for all cases except the F28X50LP filter,
where the on-orbit measurements show the sensitivity on orbit is 
77% that predicted pre-launch.  Updates to synphot and the ETC have
been made and updates to the pipeline calibration throughputs
are imminent.  The resulting accuracy of the new calibrations are about 5% 
in the FUV, 15% in the NUV, 5% for the CCD clear mode, and 10% for the 
other CCD modes. Details will be provided in a forthcoming STIS ISR
(Smith and Ferguson, 1998).

+ Geometric Traces for Echelle and First Order Modes soon to be Updated. 

We are aware that the current ground-determined echelle order traces
can benefit from updating and that the first order (L and M) mode spectral 
traces for geometric rectification of slit data require updating based 
on on-orbit measurements. We hope to have updated reference files
available and in the archive within a month or two. Check the WWW pages
and future STANs for updates. The current first order mode spectral
traces for two-dimensional rectification leave errors of +-1 pixel
across 1024 pixels.

+ On orbit CCD Spectral Flats Under Construction

The current CCD spectral flats were generated during ground calibration
and in many cases the signal-to-noise in those flats themselves limit
the signal-to-noise achievable in science data. We plan to update the
spectral flats in the pipeline and archive based on on orbit data in the next 
month or two. Again, check the WWW pages and future STANs for updates.

=====================================================================

		STIS PIPELINE AND CALIBRATION NEWS
                ----------------------------------

A new version of CALSTIS (version 1.8) has been released and is now
used the the pipeline (effective May 23, 1998).  This update, which 
also include several new tools, is available for downloading from the
STSDAS Advisories page (http://stsdas.stsci.edu/pub/stsdas).  

****************************************************************
We recommend that ALL observers download this new version of
CALSTIS as it has important updates, bug fixes, and enhancements,
as described below.
*****************************************************************

Changes that have been made to CALSTIS in version 1.8 include:

1-d spectral extraction (x1d)

Several useful processing values determined during spectral extraction
have been written to the trailer file.  These entries, listed below,
are now included the the x1d table file.

A2CENTER   default or user specified y extraction location
EXTRSIZE   size of extraction aperture
MAXSRCH    search radius for cross correlation location of extracted spectrum
BK1SIZE    size of background box 1
BK2SIZE    size of background box 2
BK1OFFST   offset of background box 1
BK2OFFST   offset of background box 2
EXTRLOCY   y pixel array of extracted spectrum location

To prolong the lifetime of the MAMAs, we are shifting the location of
the spectral images in the cross-dispersion direction on a monthly
basis (see the MAMA Phase II update).  This offsetting start in
January 1998, and the offset values are stored in the keywords
MOFFSET1 and MOFFSET2.  These keywords were not being properly read,
so a zero offset was being used by calstis-6 (x1d).  These keywords
are now being properly accessed.  Note for the first order data, this
error does not impact your data (since the finding algorithm searches
the entire detector for your spectrum), but for echelle modes, this
error can cause orders to be mis-extracted in cases where the shift
put the order beyond the search region. We are presently reprocessing
all the impacted echelle observations, and will have the corrected
files placed in the archive and email sent to the appropriate PIs so
they can retrieve the recalibrated data. We expect the recalibrated
data to be available in the archive in a few weeks. Note that this
problem only affected GOs with echelle data taken after January 1998.

Wavelength calibration (wavecal)

If a science observation and its associated wavecal were taken with
different apertures, the offset between those apertures was being
taken into account twice, thus resulting in an improper wavelength
calibration (typically of order 1 pixel).  This problem has been
corrected. GOs requiring accurate wavelength scales for observations
where the science data and automatic wavecals were taken through
different slits (which will be the case for observers using slits
which are >= 0.5 arcseconds wide) will want to recalibrate their data.

Reference file processing for MAMA observations with Doppler Applied

The computation of the Doppler shift for convolving reference files 
originally had the incorrect sign; this has not been corrected.
The affect of this sign problem is to reduce the signal-to-noise
in the calibrated data for echelle and first order M mode data taken
with the NUV-MAMA. FUV-MAMA and first order L mode data is
unaffected (the former because no flat is applied currently in the
pipeline).

A number of additional enhancements and minor problem fixes include:

o when processing a reference image which requires binning, calstis will
  no longer print warning messages about new keywords being added to the
  header (since the binned reference file is not saved).

o if an invalid detector name is in the header, calstis will now stops
  rather than assuming a default detector.

o if no output file name is given, the input file name is used to determine
  the output names.  Calstis now properly modifies the input file name to 
  remove the directory prefix if one is given.

o when running x1d, the output name can now be omitted, and the input
  name will be used to define the output name.

o the calibration switches are now case insensitive (e.g. OMIT or omit).

o it is now possible to perform flux calibration (during 1-d extraction)
  without performing background subtraction.

New tools released with CALSTIS version 1.8 include:

tastis:
The iraf task 'tastis' analyzes STIS target acquisition images. It prints
general information about the target aquisition datafiles of type ACQ and
ACQ/PEAK, computes the partial and final slews performed during the
acquisition, and provides warnings of possible problems which could
indicate a failure of the acquisition.


ocrreject:

The task ocrreject has been edited to include a switch that will allow the
calibration of either all the input files into 1 cosmic-ray rejected
image, or to create 1 output image per input file provided that each input
file contains more than 1 imset to properly combine their imsets into 1
cosmic-ray rejected image per datafile.
It also takes wildcards the same way the other calstis tasks do. 

daydark - a task to create a daily dark 

Tasks to create a fring flat (see the more detailed write up
on Defringing G750L and G750M data, below).
normspflat 
prepspec
mkfringeflat
defringe

pp_dads - this task is used to generate paper products, and has been
significantly enhanced (particularly to show 1-d extracted spectra)

=====================================================================
 
			ANALYSIS NOTES
                        --------------

+ Cosmic ray rejection for F28X50LP, F28X50OII, and F28X50OIII filters

For those filtered CCD imaging observations with a high sky
background, the pipeline cosmic ray rejection algorithm may not
properly remove all comsic rays as pointed out by a recent GO.  
This is due to a problem with the sky subtraction that is performed prior 
to the rejection.  The CDD filters are 28"X51" in size, while the full 
field-of-view is 51"x51". The pipeline presently does not mask out the 
unexposed portion of the detector, which could cause an undersubtraction of 
the sky (i.e. the unexposed portion skews the average towards too small a
value).  If this happens for only one of the images in a CR-SPLIT
observation, then that image would have artificially high count
values, which could be considered as cosmic rays by the software.

If you feel that cosmic ray rejection was not done properly on your
observations (i.e. the image does not look clean), you should display
the data quality extension of the corresponding flt file.  If that
data shows a large number of pixels flagged as bad (i.e. if the image
shows many pixels with positive values), then you have likely been
impacted by the sky subtraction problem.  Until we can update our
software to mask out the unused portion of the detector, there is a
simple workaround to correct the problem.  Recalibrate your data (the
flt file) with the ocrreject task with sky subtraction turned off
(SKYSUM=NONE).  This should do a good job at removing most the cosmic
rays (although some very low level ones may remain) from the data.
Note that turning off background subtraction at this phase of the
processing will NOT impact your photometry, as the subtracted sky is
added back into the crj image after the cosmic rays have been removed.

+ Defringing Software For G750L and G750M

Four new IRAF cl tasks have been delivered to the STIS package within STSDAS 
for the purpose of de-fringing STIS G750L and G750M spectra:

(1) NORMSPFLAT   for normalizing fringe flat images
(2) PREPSPEC     for preparing science spectra for de-fringing
(3) MKFRINGEFLAT for optimizing the (normalized) fringe flats in terms
                 of (a) shifts along the dispersion and (b) scaling of the
                 amplitudes of the fringes (i.e., correction for differences
                 in scattered light between the fringe flat and the science
                 spectrum)
(4) DEFRINGE     for performing the actual de-fringing correction

In the first task, NORMSPFLAT, the input flat field image is first run
through the STIS pipeline (calstis) in order to perform bias
subtraction, cosmic ray rejection, dark subtraction, and division by a
pixel-to-pixel flat field. In case of G750M data, wavelength
calibration and S-distortion correction is performed as well, so that
a wavelength calibration image (wavecal) has to be provided for G750M
spectra as well (parameter "wavecal"). An appropriate superdark file
name has to be provided as parameter "darkfile", and the
pixel-to-pixel flat field as parameter "pixelflat". This
pixel-to-pixel flat field should NOT contain any fringes. A good
choice is e.g., the 50CCD (clear) pipeline flat field (to be retrieved from 
the archive). The input flat field image is subsequently normalized to
unity in the illuminated part of the image by an appropriate spline
fit to the lamp function. The illuminated part of the image is derived
from the value of the "aperture" keyword in the main header of the
input flat field image. This normalization is done on a line-by-line basis.  

The task NORMSPFLAT allows the user to bypass the whole calstis
reduction step described in the previous paragraph through boolean
switch "do_cal". In case "do_cal" is set to "no", make sure that
the input flat field image has been corrected for pixel-to-pixel
sensitivity variations with the proper pixel-to-pixel flat field. 

The second task, PREPSPEC, prepares the science spectrum for defringing by 
running the STIS pipeline (calstis) on it, just as described above for the 
fringe flat field. Again, an appropriate superdark file name has to be 
provided as parameter "darkfile", and the pixel-to-pixel flat field as 
parameter "pixelflat"; for G750M spectra, a wavelength calibration image 
(wavecal) has to be provided for G750M spectra as well (parameter "wavecal"). 
PREPSPEC has to be executed BEFORE attempting to use the tasks MKFRINGEFLAT 
and DEFRINGE, cf. below.

The main goal of the third task, MKFRINGEFLAT, is to determine the
best match between the location and shape of the fringes in the input
flat field image and those in the science spectrum. The match is made
in two separate steps, which can be issued independently by means of
boolean switches: (a) determine the offset along the dispersion
direction between the flat field image and the science spectrum, and
(b) determine the best match between the fringe amplitude in the flat
field image with the fringe amplitude in the science spectrum. This
last matching procedure is equivalent to a correction for the
difference between the scattered light in the flat field image and
that in the science spectrum. In the case of spectra of point sources, this 
latter correction is different from spectra of diffuse sources. The user is 
therefore encouraged to perform a few iterations on the range of the amplitude 
scaling parameters (see the help pages of MKFRINGEFLAT).

The fourth and last task, DEFRINGE, performs the actual de-fringing 
correction. It divides the science spectrum by the fringe flat that was 
prepared in advance using NORMSPFLAT and (ev.) MKFRINGEFLAT.

All four tasks are designed to work for all central wavelength settings of the 
G750L and G750M gratings.


+ Recalibration and Rearchiving of Mis-Calibrated Echelle Data

All echelle science data taken between February 1998 and June
1998 was subject to improper one-D spectral extraction due to
the bug fixed in calstis 1.8 where the MAMA monthly offsets
were not being properly read from the science header. With
the delivery of calstis 1.8, we have also recalibrated and
rearchived all echelle data taken during the trouble period.
GOs who received echelle data during that time period are
encouraged to retrieve the recalibrated data. The latest
echelle sensitivity curves (pht files) have been used
to recalibrate these data.

======================================================================

			REFERENCE FILE UPDATES
                        ----------------------

+ First Order M Mode and Echelle Sensitivity Calibration Complete

The initial calibration of the first order medium resolution (G140M,
G230M, G230MB, G430M, and G750M) sensitivities is now complete and new
photometry tables (pht filtes) have been delivered to the pipeline,
synphot, and the ETC.  The previous sensitivies in the pipeline were
ground-based measurements, and the new on-orbit values differ by a
factor of 1-2; see the STIS Reference File History web page for
comparison plots, as well as STIS ISR 92-21, in preparation.

Updated photometry tables for the echelle modes (E140M, E140H, E230M,
and E230H) is also complete and delivered.  For the E140M and E140H
gratings, the new throughputs differ by a factor of 1-2 from the
previous values, while for the E230M and E230H gratings, the
difference is slightly less (1-1.5); see the STIS Reference File
History web page for comparison plots, as well as STIS ISR 98-22 (in
preparation).

The throughputs in the PHOTTAB reference file (such as those mentioned
above) are for an "infinite" extraction height.  To correct for the
fact that the real extractions heights are finite, the PCTAB reference
file (pct) was added in calstis v1.7, and the values for the low
resolution modes were delivered at that time.  We have now completed
the initial delivery of the photometric correction tables for the
medium resolution and echelle modes.

In the February STAN, we recommended that people with first order low
resolution data recalibrate their data to take advantage of
enhancements to the calstis software, as well as the delivery of the
improved sensitivity files.  This recommendation is now extended to
those with medium resolution and echelle data (see the note on calstis
v1.8 for more on echelle observations).

+ Upcoming Reference File updates

We plan to update the following reference files within the next 3 months:

Dispersion coefficient files (dsp) for E140H (1453), G230M (1713),
	and G750M (9806. 9851, and 10363) - impacts wavelength scale.

Echelle trace files (sptrctab) for all E modes - impacts photometry at
	ends of orders.

Aperture description table (adp) - impacts the wavelength scale
	for slitless spectroscopy using full field apertures.

Imaging throughputs (pht) - impacts photometry for imaging modes.

1st Order Spectral Traces/Geometric Distortion (1dt) - impacts two
	dimensional rectification for extended source data.

CCD Spectral Flats (pfl) - impacts signal-to-noise achievable.


====================================================================

			OBSERVATION PLANNING
                        --------------------

+ Target Coordinates and Confirmation Charts

Some PIs have encountered target confirmation charts where the target
is not centered on the cross hairs even though double checking the
coordinates shows them to be correct. Here is one possible source of
confusion: If you supplied a proper motion for the target the proper
motion has been applied to the coordinates so that the cross hairs
appear where your target will be in the year 2000.  The chart itself
shows the sky for the epoch of the guide star plate. The discrepency
should be the amount that the target will move between the epoch of
the plate and the year 2000.

More generally we remind GOs that accurate source positions in the
GSSS reference frame must be provided in your Phase 2 proposal to assure
that the target will appear in the initial acquisition subarray image, 
which is 5" x 5".

+ Exposure Time Calculator Updates

Echelle mode scattering correction factors have been updated in the 
Spectroscopic ETC based on the latest on-orbit echelle mode calibration data. 
New synphot throughput files for e140h, e140m, e230h and e230m were also 
generated from the on-orbit calibration data and are now being used by 
the ETCs. Another update to the echelle throughputs is expected in the next 
few weeks which will include more accurate representation of the
signal-to-noise acquired in the overlap regions from order to order. 

As noted above, synphot  and etc throughput files for the first order M 
have also been recently updated for on-orbit calibration data.
 
The background tables in all the ETCs have been updated so that the 
geocoronal line emissions are more representative for the STIS observations.
 
The image-mode throughputs have been updated based on on-orbit calibrations 
forthe following filters: f25ciii, f25cn270, f25mgii, f25qtz, f28x50lp, 
f25cn182,f25lya, f25nd3 and f25srf2. 

+ New Cycle 8 STIS Instrument Handbook Imminent

The NEW Cycle 8 STIS INSTRUMENT HANDBOOK is almost ready and
should be available and in libraries near you by mid June. The Handbook
will have been almost totally updated based on on-orbit experience and
calibration, and we recommend you refer to it for all future observational
planning. (It must be used, of course, for all Cycle 8 Phase I proposing.)

==================================================================
 
			STIS DOCUMENTATION
                        ------------------
 
All new STIS related documentation noted here, along with previous
items, may be found on the "Documentation" link off the STIS Home
Page.

 
STIS ISRs (Instrument Science Reports)...
-----------------------------------------


  98-19: STIS Near-IR Fringing. II. Basics and Use of
         Contemporaneous Flats for Spectroscopy of Point Sources. 
         Paul Goudfrooij, Ralph C. Bohlin, Jeremy R. Walsh, Stefi A. Baum 
         10 May 1998 

  98-16: Use of FP-SPLIT Slits for Reaching High
         Signal-to-Noise with MAMA Detectors 
         Ronald L. Gilliland 
         09 Apr 1998  

  98-15: MAMA Flat-field Status and Plans 
         Dick Shaw, Mary Elizabeth Kaiser, and Harry Ferguson 
         06 Apr 1998  

  98-14: The Calstis IRAF Calibration Tools for STIS Data 
         Rocio M. Katsanis, Melissa A. McGrath, STIS Pipeline Block 
         26 Apr 1998

  98-13: Calstis7: Two-dimensional rectification of
         spectroscopic data in the STIS Calibration Pipeline 
         Melissa McGrath, Phil Hodge, Stefi Baum 
         5 May 1998 

  98-12: Calstis4, calstis11, calstis12: Wavecal Processing in the STIS 
         Calibration Pipeline; Phil Hodge, Stefi Baum, Melissa McGrath, 
         Steve Hulbert, Jennifer Christensen 
         22 Apr 1998 

  98-11: Calstis2: Cosmic Ray Rejection in the STIS Calibration Pipeline 
         R. Shaw, J.C. Hsu, Spectrographs Pipeline Block 
         4 May 1998  

  98-10: Calstis0: Pipeline Calibration of STIS Data- A Detailed View 
         Phil Hodge, Stefi Baum, Melissa McGrath, Dick Shaw 
         22 Apr 1998  

  98-09: Extraction Heights for STIS Echelle Spectra 
         Claus Leitherer and Ralph Bohlin 
         15 Apr 1998  

  98-06: STIS CCD Anneals 
         Jeffrey J.E. Hayes, et. al. 
         01 Mar 1998  



==============================================================================
 
                                GHRS NEWS
                                ---------

The GHRS diode response file f5o1134cz.r0h was incorrectly refering to 
detector 1 and 2, whereas it should refer to detector 1 only. The correct diode
response file for detector 2 is g2e08350z.r0h. As a result, the file
g2e08350z.r0h was never used by calhrs. The problem was uncovered and reported 
to us by a GHRS user. This error resulted from an erroneous multiple delivery
of the f5o1134cz.r0h file. The problem has been corrected and StarView bestref
now gives the correct diode response files for detectors 1 and 2. 


==============================================================================
 
                                FOS NEWS
				--------

A comprehensive description of FOS polarimetry principles, 
file formats, the FOS closeout polarimetry calibration and accuracies, 
and general polarimetry advice is now available in newly released  
FOS Instrument Science Report 150.  Correction for COSTAR-induced 
polarization is now available in calfos  (see FOS Pipeline and Software
below).

All FOS polarimetry observations have been re-calibrated with the 
FOS closeout polarimetry calibration reference files and the data have 
been re-delivered to the HST Archive.  A summary of this re-calibration is 
presented in FOS ISR 150.  One-sigma linear polarization 
limiting accuracies are about 0.3 percent (pre-COSTAR) and 0.5 percent 
(post-COSTAR).
  
FOS ISR 150 is available from the FOS WWW page in both 
PDF and Postscript formats; hardcopies may be obtained from the SSD 
Helpdesk (email: help@stsci.edu).

+ CALFOS UPDATES - the updated CALFOS and ASSOCIATED tasks can be downloaded
	from the STSDAS Advisories page (http://ra.stsci.edu/pub/stsdas).  

 Spectropolarimetry
 ------------------
 The 'calfos' task has been upgraded to incorporate the application of
 post-COSTAR spectropolarimetry calibration corrections.  If the   
 spectropolarimetry data were acquired during the post-COSTAR epoch, as 
 indicated by the Science header keyword/value pair, KYDEPLOY=T, and a 
 post-COSTAR calibration is available for the particular 
 detector/grating/polarizer/aperture combination, the post-COSTAR polarimetry 
 correction reference file, 'PCPHFILE', is required for a proper calibration.  

 However, it should be noted that if no post-COSTAR polarimetry calibration 
 file for the 'PCPHFILE' calibration file keyword entry is provided, 'calfos' 
 will not abort.  Instead, warning messages will be issued and the data in the 
 output 'c3h' file will still be calibrated, but the additional post-COSTAR 
 correction will not have been applied.

 The 'ckwfos' pset, which is used in conjunction with the 'chcalpar' task
 to update the calibration parameters in the Science header, has been upgraded 
 to contain the new 'PCPHFILE' entry.
    
 Error
 -----
 An error in addressing the consistency of the calibration processing 
 switches that applies ONLY to spectropolarimetry data  
 was fixed in 'calfos'.  There was a conflict between the 
 original flux calibration (FLX_CORR), which is now used only for 
 polarimetry data, and the standard method of flux calibration 
 (AIS_CORR, TIM_CORR, APR_CORR).  Prior to this correction, if any of the 
 standard method calibration switches were turned on, FLX_CORR was always 
 set to OMIT - even for spectropolarimetry data.  However, the standard  
 method of calibration is not applicable for spectropolarimetry data.  The
 old logic could result in the spectropolarimetry data not being flux 
 calibrated at all.  Now FLX_CORR is always used for polarimetry flux 
 calibration.

 CALPOLAR
 --------
 The 'calpolar' task in the 'spec_polar' package has been upgraded to 
 incorporate the application of post-COSTAR spectropolarimetry calibration 
 corrections.  The implementation of the post-COSTAR spectropolarimetry 
 calibration in 'calpolar' is identical to that of 'calfos'.
 
============================================================================
 
                Data Analyst Position Available at STScI
                ----------------------------------------
 
The Space Telescope Science Institute currently has openings for
Data Analysts. Data Analysts in the Science Support Division help General
Observers and Archive Researchers analyze HST data, work with Instrument
Scientists in calibrating the HST instruments, and work with STScI staff
on grant-supported research projects. These research projects span a range
of size scales from comets and planets to the large scale structure of
the universe and a range of wavelengths from radio to X-ray astronomy.
 
Applicants should possess a B.S. degree (M.S. degree a plus) in astronomy
or physics, or equivalent; experience with astronomical research; familiarity
with scientific computing; expertise in data analysis; knowledge of IRAF, IDL
or other software packages for astronomical data analysis; and programming
ability. Additional mathematical, statistical, and computer skills are
desirable. Candidates should have the ability to work with a minimum of
direction, enjoy research, and possess skills to develop excellent working
relationships. Candidates should send a cover letter with current curriculum
vitae and the names of three references to:
 
Human Resources Manager
Space Telescope Science Institute
3700 San Martin Dr.
Baltimore, MD 21218
 
Women and minorities are strongly urged to apply. AAE/EOE.

============================================================================
 
                         RECENT PREPRINTS
                         ----------------
 
We draw your attention to these papers, based on STIS, FOS and GHRS data, that
will appear in the next few months.  This list includes all preprints received
by the STScI Library not yet published in the journals.  Please remember to
include our Library in your preprint distribution list.

KORATKAR, A.; ANTONUCCI, R.; GOODRICH, R.; STORRS, A.
"Below the Lyman Edge: UV Polarimetry of Quasars"  ApJ accepted
http://www.stsci.edu/science/preprints/prep1233/prep1233.html

MAOZ, D.; KORATKAR, A.; SHIELDS, J.C.; HO, L.C.;
FILIPPENKO, A.V.; STERNBERG, A.  "The Ultraviolet Spectra
of LINERs: a Comparative Study"  AJ 7-98

JAMES, P.B.; HOLLINGSWORTH, J.L.; WOLFF, M.J.; LEE, S.W.
"North Polar Dust Storms in Early Spring on Mars"  JGR
 
===========================================================================
 
                 APPENDIX: HST Spectroscopy Contacts
                 -----------------------------------
 
Any questions about the scheduling of your observations should be
addressed to your Program coordinator. Post-Observation questions can
be addressed to your Contact Scientist. If you do not know who these
persons are, you can find the information on the WWW at
http://www.stsci.edu/public/propinfo.html.
 
Analysis, STSDAS or any other HST-related questions can also be
addressed to help@stsci.edu
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