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WFPC2 STAN

S T A N / W F P C 2 - Number 21, November 1996

CONTENTS:

Bug in Pipeline Reduction of some Single-chip WFPC2 Images:

-Stefano Casertano, Sylvia Baggett, Massimo Stiavelli, J. C. Hsu

A bug has just been discovered in the pipeline calibration software for a small fraction of WFPC2 images. This bug was introduced in the December 1994 version (V. 1.3.0.7) of the CALWP2 program, and affects the processing of all single-chip, non-PC images, produced by the non-standard (engineering only) options READ=2, READ=3 or READ=4. As a consequence of the bug, the calibration proceeds as if the first group represents the PC (DETECTOR=1), regardless of the detector actually used. The steps affected are the bias subtraction BIASCORR (NOT the bias level subtraction BLEVCORR), the dark subtraction DARKCORR, the flat fielding FLATCORR, and the shutter shading correction if applicable. As a consequence, the pixel noise may be larger than in a correctly reduced image, and an offset zero point of several percent may exist. Also, images taken with partially rotated, quad, or Woods filters may have an incorrect vignetting function applied, which may result in significant non-uniformity of the background and of the throughput.

A new version of the calibration routine CALWP2 is now being tested, and should become available in about four weeks. Meanwhile, if you have single-chip images in one of the WF cameras and you suspect the incorrect calibration program was applied, please contact help@stsci.edu. GOs affected by the problem have been informed directly.

Impact of November Safing Event on Repeats of Failed Observations:

-R. Downes

Since during the upcoming Servicing Mission in February 1997, FOS and GHRS will be removed from HST, we gave the highest priority to observations using those instruments. This required us to schedule all programs with those instruments as early as possible, as well as other observations that for scientific reasons needed to be scheduled in the first half of Cycle 6. This had resulted in a very full long range plan, but one which we were optimistic to complete prior to the Servicing Mission. However, with the safing event in early November, we now find that completion of all the high priority programs is in doubt. For this reason, we will place all observations approved for repeats in a contingency pool, which will be utilized in case of a launch slip. We will also do our best to schedule as many of these pool observations as possible prior to the Servicing Mission whenever they can be fit into upcoming observing calendars.

We regret not being immediately able to reschedule failed observations, but there is unfortunately not enough time left before the Servicing Mission to allow us to do this. Hopefully we will be able to re-insert many of the programs back into the schedule.

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.

RETTIG, T.W.; MUMMA, M.J.; SOBCZAK, G.J.; HAHN, J.M.; DI SANTI, M.
"The Nature of Comet Shoemaker-Levy 9 Sub-nuclei from an Analysis of
Pre-Impact HST Images"  Journal of Geophysics Research - Planets, 101, 
9271-9282, 1996.

HAHN, J.M.; RETTIG, T.W.; MUMMA, M.J. "Comet Shoemaker-Levy 9 Dust"
Icarus 121, 291-304, 1996

RETTIG, T.W.; SOBCZAK, G.J. "Dust Outflow Velocity of Comet 
Shoemaker-Levy 9" Icarus 121, 281-290, 1996

DA COSTA, G.S.; ARMANDROFF, T.E.; CALDWELL, N.; SEITZER, P.
"The dwarf spheroidal companions to M31: WFPC2 observations
of Andromeda I"  AJ 12-96

FALAMO, R.; URRY, C.M.; PESCE, J.E.; SCARPA, R.;
GIAVALISCO, M.; TREVES, A.  "HST observations of host
galaxies in three radio-selected BL Lacertae objects"  ApJ
2-1-97

FERRARO, F.R.; CARRETTA, E.; CORSI, C.E.; FUSI PECCI, F.;
CACCIARI, C.; BUONANNO, R.; PALTRINIERI, B.; HAMILTON, D.
"The stellar population of the globular cluster M3. II. CCD
photometry of additional 10,000 stars"  A&A accepted

FREEDMAN, W.L.; MADORE, B.F.; KENNICUTT, R.C.  "Hubble
Space Telescope key project on the extragalactic distance
scale"  Extragalactic Distance Scale
 
HU, E.M.; MCMAHON, R.G.; EGAMI, E.  "Galaxies at z > 4.5"
HST and the High Redshift Universe astro-ph/9609188

HUNTER, D.A.; LIGHT, R.M.; HOLTZMAN, J.A.; LYNDS, R.;
O'NEIL, E.J. JR.; GRILLMAIR, C.J.  "The intermediate mass
stellar population of the Large Magellanic Cloud cluster
NGC 1818 and the universality of the stellar initial mass
function"  ApJ accepted                        

SAKAI, S.; MADORE, B.F.; FREEDMAN, W.L.; LAUER, T.R.;
AJHAR, E.A.; BAUM, W.A.  "Detection of the tip of the red
giant branch in NGC 3379 (M105) in the Leo I group"

FORBES, D.A.  "HST imaging of globular clusters in
kinematically-distant core ellipticals"  Nature of
Elliptical Galaxies

MINNITI, D.; MEYLAN, G.; PRYOR, C.; PHINNEY, E.S.; SAMS,
B.; TINNEY, C.G.  "An unusual brightening of the eclipsing
binary star AKO 9 in the globular cluster 47 Tucanae
observed with HST"  ApJ accepted

STRUCK, C.; APPLETON, P.N.; BORNE, K.D.; LUCAS, R.A.  "Hubble Space
Telescope Imaging of Dust Lanes and Cometary Structures in the Inner
Disk of the Cartwheel Ring Galaxy", 1996, AJ, 112, 1868.

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. 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 questions can also be addressed to help@stsci.edu.

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