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Hubble Space Telescope
WFPC2 STAN

S T A N / W F P C 2 - Number 13, March 1996

CONTENTS:

Small Improvement in the F170W Throughput for the Planetary Camera as a Function of Time

by Brad Whitmore

An examination of our monthly throughput monitoring shows a small increase in the throughput of the F170W filter for data taken on the PC (Planetary Camera), based on data taken since April 24 1994. The correlation can be well represented by a linear increase of 4.8 +/- 0.3 % per year, and is ONLY seen on the Planetary Camera, not on the three Wide Field chips. An even larger effect is seen for the F160BW filter, but the scatter in the data makes this measurement more uncertain. A detailed writeup is currently being prepared and will be discussed in a future STAN. Please contact Brad Whitmore (whitmore@stsci.edu) if you have seen similar effects in your data.

Caution to WFPC2 GOs Using the STSDAS METRIC and WMOSAIC Tasks

by Anatoly Suchkov, Krista Rudloff, and J.C. Hsu

WFPC2 GOs using the metric and wmosaic tasks in stsdas.hst_calib.wfpc should be cautioned to check which version of STSDAS is currently installed, as older versions of these tasks will produce incorrect results. The STSDAS task metric returns RA and DEC coordinates from pixel positions. The wmosaic task creates a mosaic of the 4 chips. STSDAS version 1.3.3 (February 1995) and later versions are capable of correctly handling both WF/PC and WFPC2 images. However, STSDAS version 1.3.2 (August 1994) and earlier versions contain the plate solutions for WF/PC only, and will therefore return incorrect coordinates and mosaics for WFPC2.

The metric task in STSDAS V1.3.2 and earlier returns correct coordinates for WF/PC but returns coordinates off by up to 60 arc- seconds if applied to WFPC2 images. The error depends on which chip the target is located. PC1 is most affected because the plate scale is different, so the error can be as large as 60". WF2 is least affected since it is the reference chip, so the error is about 0.1". For WF3, the error is up to 5.6", and WF4 up to 7".

We especially caution GOs who use metric to derive target coordinates from a WFPC2 early acquisition image for subsequent FOS or GHRS observations. If an earlier version of metric is used on WFPC2 images, the target acquisition in the FOS/GHRS apertures will fail due to the large error, and the observation will be lost.

We would also like to remind users that metric must be run on individual chips, not on a mosaiced image. The most current version of STSDAS is 1.3.4 (October, 1995). We recommend that all users upgrade to this version to obtain the most accurate results.

The On-Line Calibration Database Astronomical Library:

by Luis Colina and Krista Rudloff

Several atlases consisting of both observed and model stellar catalogs as well as HST standard stars spectra are available on-line. The atlases form a fundamental database needed for several HST related activities. For instance, the atlases provide absolute standards for the calibration of HST instruments, model spectra to cover spectral ranges not available from observations, a uniform database for use with software tools such as the exposure time simulators for FOC, WFPC2, and NICMOS, and a database for use with applications such as SYNPHOT.

The on-line library includes:

- Atlases of HST Standard Stars:

* CALSPEC  (composite UV and optical absolute flux calibrated 
            reference spectra of the HST standards on the white
            dwarf scale)

* CALOBS   (original and updated versions of the UV and optical 
            spectra of the standards)
 
- Atlases of Spectrophotometric Stellar Spectra:

  * Bruzual
  * Jacoby-Hunter-Christian
  * Gunn-Stryker
  * Bruzual-Persson-Gunn-Stryker
 
- Atlases of Stellar Model Atmospheres:

  * Buser-Kurucz
  * Kurucz's 1993 atlas (new)

Tape Recorder #2 Failure

On 19 Jan. 1996, the #2 tape recorder failed on-board. While serious, it will not impact most science observations as this recorder was used for the engineering data. It will impact all engineering data for ~17 minutes of each orbit in that HST will have engineering telemetry gaps. So if something does go wrong with an observation during that time, there will be no engineering data for analysis. This also means that products like the Jitter (Observation Log) files will be incomplete. The gaps are caused by the incomplete coverage of the TDRSS satellite network on the HST orbit. Due to a "bit slip" problem from last year, this tape recorder is currently on the list of items to be replaced during the 1997 Servicing Mission. It will be replaced by a "solid state recorder" which will vastly increase the onboard data storage capacity of HST and will allow engineering data to be recorded during any TDRS gaps.

Data Analyst Position Available at STScI

The Space Telescope Science Institute anticipates several 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 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 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 WF/PC and WFPC2 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.

FORBES, D.A.; FRANX, M.; ILLINGWORTH, G.D.; CAROLLO, C.M.
"Ellipticals with kinematically-distant cores: WFPC2
imaging of globular clusters"  ApJ accepted

GRILLMAIR, C.J.; AJHAR, E.A.; FABER, S.M.; BAUM, W.A.;
HOLTZMAN, J.A.; LAUER, T.R.; LYNDS, C.R.; O'NEIL, E.J. JR.
"Hubble Space Telescope observations of globular clusters
in M31. II. Structural parameters"  AJ accepted

LAVERY, R.J.; SEITZER, P.; SUNTZEFF, N.B.; WALKER, A.R.; DA
COSTA, G.S.  "Distant ring galaxies as evidence for a
steeply increasing galaxy interaction rate with redshift"

BARTH, A.J.; HO, L.C.; FILIPPENKO, A.V.; SARGENT, W.L.W.
"A WFPC2 search for ultraviolet emission from LINERs"
Phys. of LINERs in View of Recent Obs.

BYUN, Y.-I.; GRILLMAIR, C.J.; FABER, S.M.; AJHAR, E.A.;
DRESSLER, A.; KORMENDY, J.; LAUER, T.R.; RICHSTONE, D.;
TREMAINE, S.  "The centers of early-type galaxies with HST.
II. Empirical models and structural parameters"  AJ accepted

COLLEY, W.N.; RHOADS, J.E.  "Are the HDF galaxy counts
whole numbers?"  ApJ

SAHA, A.; SANDAGE, A.; LABHARDT, L.; TAMMANN, G.A.;
MACCHETTO, F.D.; PANAGIA, N.  "Cepheid calibration of the
peak brightness of SNe Ia. V. SN 1981B in NGC 4536"  ApJ
7-20-96

APPENDIX: WFPC2 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.

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