S T A N / W F P C 2 - Number 17, July 1996

CONTENTS:

• WFPC2 NEWS:
• WFPC2 Handbook Version 4.0 in HTML.
• Improved Flat Field Reference Files.
• RECENT HST SAFEMODE EVENT
• NEW WFPC2 DOCUMENTATION:
• Several New Instrument Science Reports Are Now Available
• RECENT PREPRINTS
• APPENDIX: WFPC2 CONTACTS

WFPC2 Handbook Version 4.0 in HTML:

by J. Biretta, M. S. Wiggs, and M. Stevens

The recent version 4.0 of the WFPC2 Handbook is now available in a form that can be browsed with Netscape or Mosaic on the WWW. Users may start by either browsing the Table of Contents or the Index, and clicking on the title of the section or topic they wish to view. The text also contains active links to other portions of the document, and other documents on the WWW, where appropriate. This version may be most useful for people needing quick information on a specific topic who do not yet have a paper copy.

Improved Flat Field Reference Files:

by J. Biretta, M. S. Wiggs, and S. Baggett

Improved flat field reference files have been generated for most filters and are now being used in the calibration pipeline. The improvement affects all standard filters redward of, and including, F300W. The improvements mostly affect regions within 50 pixels of the CCD edges; the largest change is on WF3 where 8% errors are corrected near the outer corner of that CCD. Regions near the centers of the CCDs have much smaller corrections; the RMS correction is about 0.3% over the central 600x600 pixels of each CCD.

Internal consistency checks and comparisons against JHU Medium Deep Survey sky flats indicates the revised flats are accurate to be better than 0.3% on spatial scales from 0.1 to ~80 arcseconds, when applied to data taken near the middle of the monthly decontamination cycles. Further details of the generation and testing of these flats can be found in the history records attached to header of each new flat.

Lists of the new flats can be found in the "reference file" document available under the URL belowon the WFPC2 site. The flats themselves are available through the HST data archive. The new flats have names of the form "gxxxxxxxx.r4h" where "xxxxxxxx" is some arbitrary number.

Recent HST Safemode Event:

by K. Rudloff and R. Doxsey

HST entered inertial hold safemode at 17:31 UT on Saturday, July 13th. For reasons that are yet to be understood, one of the four elements of the on-board quaternion (which represents HST's idea of where it is pointed) jumped by the equivalent of 7 degrees. The sudden jump caused a loss of guide star lock just before an earth occultation. As the occultation ended, a safemode check was performed to determine whether HST was pointed at the earth. Because the quaternion was in error by 7 degrees, the check failed and safemode was entered (even though HST was sufficiently clear of the Earth and there was no risk to the FGSs). The safemode entry proceeded normally and all Instrument responses were as expected.

An investigation of the problem by flight software staff is in progress. The discontinuous jump is consistent with a single bit flip in the words holding the data, but the cause of the bit flip is still unknown. There is no simple diagnostic which can be run on the computer system without additional risk, so, for the foreseeable future, one of the on-board tape recorders will be devoted to recording engineering data. This will provide a means for diagnosing the problem in the event that it is repeated.

There have been no signs of additional problems since the event on July 13th, and HST returned to normal science operations on Wednesday evening, July 17th. STScI staff are actively modifying the schedules to fit within the constraints of using a single science tape recorder.

NEW WFPC2 DOCUMENTATION:

Several recent Instrument Science Reports are now available.

Paper copies may be requested by sending email to help@stsci.edu.

ISR 96-03 "Background Subtraction in WFPC2 Frames" (Ferguson). Determination of the background level for the purpose of performing accurate photometry.

ISR 96-05 "Wavelength/Aperture Calibration of the WFPC2 Linear Ramp Filter" (Biretta, Ritchie, Baggett, MacKenty). Provides the transformation between central wavelength on ramp filters and aperture locations in the focal plane.

ISR 96-06 "Photometric Calibration of WFPC2 Linear Ramp Filter Data in SYNPHOT" (Biretta, Baggett, and Noll). It is now possible to use SYNPHOT to provide photometric accuracy of approximately 3 % for the ramp filters.

ISR 96-07 "WFPC2 Throughput Stability in the Extreme Ultraviolet" (MacKenty, Baggett). The throughput in the Ly-alpha passband has remained unchanged with an uncertainty of about 20 %.

ISR 96-08 "WFPC2 Cycle 6 Calibration Plan" (Casertano and the rest of the WFPC2 team) - Also available in version 4.0 of the WFPC2 Instrument Handbook.

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.

BRESOLIN, F.; KENNICUTT, R.C. JR.; STETSON, P.B.  "An HST
study of OB associations and star clusters in M101"  AJ
accepted

GIAVALISCO, M.; LIVIO, M.; BOHLIN, R.C.; MACCHETTO, F.D.;
STECHER, T.P.  "On the morphology of the HST faint
galaxies"  AJ 8-96

HOLLAND, S.; FAHLMAN, G.G.; RICHER, H.B.  "Deep HST V- and
I-band observations of the halo of M31: evidence for
multiple stellar populations"  AJ accepted

BURBIDGE, E.M.; BEAVER, E.A.; COHEN, R.D.; JUNKKARINEN,
V.T.; LYONS, R.W.  "AO 0235+164 and surrounding field:
surprising HST results"  AJ

BURROWS, C.J.; STAPELFELDT, K.R.; WATSON, A.M.; KRIST,
J.E.; BALLESTER, G.E.; CLARKE, J.T.; CRISP, D.; GALLAGHER,
J.S. III; GRIFFITHS, R.E.; HESTER, J.J.; HLESSEL, J.G.;
HOLTZMAN, J.A.; MOULD, J.R.; SCOWEN, P.A.; TRAUGER, J.T.;
WESTPHAL, J.A.  "HST observations of the disk and jet of HH
 30"  ApJ accepted

MORSE, J.A.; BLAIR, W.P.; DOPITA, M.A.; HUGHES, J.P.;
KIRSHNER, R.P.; LONG, K.S.; RAYMOND, J.C.; SUTHERLAND,
R.S.; WINKLER, P.F.  "Hubble Space Telescope observations
of oxygen-rich supernova remnants in the Magellanic clouds.
I. Narrow-band imaging of N132D in the LMC"  ApJ

TRAMMELL, S.R.; GOODRICH, R.W.  "Hubble Space Telescope and
ground-based imaging of the bipolar proto-planetary nebula
M1-92: evidence for a collimated outflow"  ApJ accepted

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.

Analysis, STSDAS or any other questions can also be addressed to help@stsci.edu.

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