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Space Telescope Imaging Spectrograph
STAN - March 1997

             |        SSS  TTTTTTT  IIIIIII    SSS        |
STScI        |       SS       T        I      SS          | STAN - STIS
Analysis     |        SS      T        I       SS         | Number 1
News         |         SS     T        I        SS        | March 1997
             |       SSS      T     IIIIIII   SSS         |
        - STIS NEWS 
          + Keeping up to Date with STIS
          + User's Guide to Target Acquisition
          + Frequently Asked Questions for Phase II
          + RPS2 On-line Resources for STIS Phase II Proposal Preparation
          + OIII Filter Red Leak
          + SMOV Plans
Keeping up to Date with STIS
STIS, the Space Telescope Imaging Spectrograph, is a second generation 
instrument which was installed on HST during the February 1997 servicing 
mission.  During the next few months, the instrument will undergo a series of
tests to assure functionality as well as refine the alignments and adjustments
necessary to provide the highest quality science possible.  Early SMOV 
activities for STIS have been proceeding well; the corrector has been used 
to perform an initial focus, the performance of the CCD has been verified, 
early calibration spectra have been taken, and we are about to proceed with 
the commissioning of STIS's target acquisition and peakup modes.  For more 
information about SMOV, see the article on SMOV plans in this STAN. 
Throughout this process, and continuing for the lifetime of the instrument, 
we will be issuing monthly STANs for STIS containing status reports, problem 
advisories and information about new capabilities, calibration analyses, 
tools for the users and pointers to new postings on the STIS WWW page.   
If you are not on the STIS STAN email distribution listing and would like to 
regularly receive the STIS STAN, please see the subscription instructions
in the Appendix.
You may stay abreast of the latest news and important announcements, as well 
as review related STIS documents on the instrument, proposal preparation, 
frequently asked questions and contacts by visiting the STIS WWW page at:
Information contained in the various links to this page will be updated on a
continuing basis.  
The STIS CCD Phase II proposal deadline is March 28.  Some information related
to Phase II proposal preparation is contained within this STAN.  For additional
details or advisories on preparing and submitting your proposals, please 
look at the relevant pages on the web noted below, or contact your Program
Coordinator or Contact Scientist should you have queries needing a timely 
response.  A Phase II STIS MAMA Instrument Update will be provided
March 31, in conjunction with the release of RPS2 7.1, in support of
the Phase II MAMA proposal deadlines in May. That update will contain the
latest instrument information for those preparing MAMA proposals and will be
mailed to PIs and posted to our STIS WWW pages.
If you have questions or comments about the contents of the STAN,
our WWW pages or information posted there, general STIS questions
not directly associated with your Phase II submission, or requests
for documentation, please email and we will answer you 
User's Guide to Target Acquisition
A new "User's Guide to Target Acquisition with STIS" will be available
March 17 on the STIS WWW page (see "How to fill out a Phase II for
STIS").  This Guide expands on the target acquisition chapter in the
Instrument Handbook, and includes updated information on the exposure
time requirements, as well as a step-by-step process for formulating
your target acquisition exposure(s).  We also present examples for
several types of targets, and discuss how to use the new STIS Imaging
Exposure Time Calculator and Target Acquisition Simulator in
determining your acquisition plan. 
Frequently Asked Questions for Phase II
We have included new Frequently Asked Questions (FAQs) specific to Phase 
II submissions on the STIS WWW page. The FAQs are grouped by category 
(Bright Object Protection, S/N and Observing strategies, Scheduling 
constraints, RPS2, Exposure Time Calculator, Target Acquisition, 
Calibration, Change request/Duplications, and Policies), and will be 
continually updated as we learn more about the instrument (from SMOV) 
and about problems encountered in completing Phase II submissions.
RPS2 On-line Resources for STIS Phase II Proposal Preparation 
Several on-line resources for Phase II proposal writing and RPS2 help are
currently available.  Among these are the proposal instructions with examples
of STIS proposals included, RPS2 advisories, and other STIS related instrument
news links.  All the information noted below may be found through links off
the STIS Home Page under the `Proposal Resources' section.
  o  STIS chapter of Phase II Proposal Instructions:
     This is the basic reference for putting together a proposal with RPS2 and
     may be found via links in the `How to Prepare' section of the `Proposal 

  o  Exposure Time Calculator (ETC) for Spectroscopic and Imaging targets;
     Target Acquisition Simulator (link to proposal resources from STIS web 
     Go to the `Tools' section for links to these software tools on the STIS 
     web site.
  o  Example proposals {especially helpful for first time proposers}:
     These examples correspond to the sample STIS worksheets provided in the 
     Phase I Call for Proposals.  See the link in the `How to Prepare' section 
     of the `Proposal Resources' page.
  o  RPS2 Advisories, work arounds and new software release schedules:  
     If you encounter problems with RPS2, check the advisories page to see if 
     there is a work around or explanation posted.  A link to this information
     may be found under the `Documents to Consult' section of the STIS Home
OIII Filter Red Leak
The STIS OIII filter (F28X50OIII) has recently been found to have
a red leak. Observers planning OIII imaging observations with STIS
or target acquisition exposures utilizing this filter need to be aware of 
this (note this information supersedes that provided in the Phase II CCD 
Instrument Update issued in February). Original ground calibration tests had 
calibrated the filter out to wavelengths of about 1030 nanometers and had shown 
no signs of a red leak. However, examination of flat field exposures taken 
through the filter revealed unexpectedly high counts, leading to the suspicion 
of a red leak at even greater wavelengths. Working with the STIS Instrument 
Definition Team, Ball Aerospace measured the transmission of a witness sample 
OIII filter from the same coating run as the flight filter.  This filter is 
not perfectly representative of the flight part so conclusions regarding the 
details of the long-wave transmission should be viewed as not perfectly 
representative of the flight part. Nevertheless, it is clear that the filter 
has a strong red leak over a narrow band centered at roughly 1110 nanometers 
with a width of roughly 60 nanometers, and a filter only transmission of 
roughly 80% at the peak. The STIS detector efficiency itself has of course 
dropped precipitously at these wavelengths.
The STIS Imaging Exposure Time Calculator has been updated to include the 
new long wavelength transmission curve. Integrated (end-to-end including
the detector and optical path throughputs) filter transmission curves for all 
the STIS CCD Imaging modes are posted (as postscript and ascii files) on the 
"Calibration Resources" section of the STIS web page.
While the [OII] filter (F28X50OII) does not show evidence for a strong
red leak at long wavelengths, a witness sample for this filter will
also be scanned out at Ball and we will post the results to the Calibration
Resources section of the STIS web page when it becomes available.
SMOV Plans
STIS is now in the midst of its on orbit commissioning as part of
Servicing Mission Orbital Verification (SMOV), carried out as a joint
effort by the STScI and the STIS Instrument Definition Team. 
Basic operations of the CCD, lamps, and mechanisms have all been checked out.  
The CCD read noise and dark current measurements are consistent with those 
listed in the phase-II update sent out in February. The absolute sensitivity 
calibration has not yet been performed, but indications from the internal lamps 
and a single external target are that the throughput is very similar to
pre-flight predictions. As for cosmic-rays, a preliminary estimate is
that 38 pixels/sec over the whole array are affected.  This is
consistent with predictions made by scaling WFPC2 measurements to the
larger physical size of the STIS CCD pixels, but this means that for a given 
exposure time the 1024x1024 pixel STIS CCD will have roughly 3 times as many 
cosmic rays as a single 800x800 pixel WFPC2 chip.  Observers will want to 
ensure they have CR-SPLIT their STIS CCD exposures accordingly.
During the early commissioning activities in SMOV, an electrical
component associated with the control electronics for the STIS MAMA
detectors was found to be more susceptible than expected to upsets
induced by particle radiation during passage through the South Atlantic
Anomaly (SAA). Engineering teams are working to characterize the nature
of the upsets and provide needed changes to our operating procedures
(e.g., turn off of the detectors during SAA passages) and enhancements
to the STIS FSW to protect against the possibility of upsets outside of
the SAA.  To be on the safe side, first turn-on of the high voltage on
the MAMA detectors will be held off until the solutions have been fully
implemented in the flight and ground support software. The current
expectation is that this will delay the initiation of the MAMA SMOV
activities by one to two months.  Essentially no impact is anticipated
to the science that can be done with the STIS MAMAs.  The Phase II
deadlines for MAMA observers remain unchanged.  More information for
MAMA observers will be provided in the Phase II STIS MAMA Instrument
Update to be issued March 31, 1996. 
Further information on SMOV calibration plans can be found 
under the "Calibration Resources" section of the STIS web page.
For weekly information on the progress of SMOV you can access the
HST Instrument Status Report, through the Observing with HST page on
the STScI web server at

While we perform many of the basic calibrations needed for
commissioning during SMOV, many calibration activities will be carried 
out either for the first time or more fully during cycle-7. Detailed 
planning for cycle-7 calibration is now starting in earnest. If you have 
questions or comments about calibration activities not described on the web, 
please send email to, or ask your Contact Scientist.
                      APPENDIX: STIS 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
Analysis, STSDAS or any other questions can also be addressed to
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