S T A N / W F P C 2 - Number 51, March 2002

CONTENTS:

• WFPC2 NEWS:
• WFPC2 Cycle 11 Calibration Program
• WFPC2 Resumes Normal Operations After Servicing Mission 3B
• Updated WFPC2 Flatfield Reference Files for 1995 - 2001 (ISR 01-07)
• Calibration Workshop Notice
• RECENT PREPRINTS
• APPENDIX: WFPC2 CONTACTS

WFPC2 Cycle 11 Calibration Program:

WFPC2 Cycle 11 Calibration Program - An invitation for user input:

The WFPC2 team is in the process of preparing the Cycle 11 Calibration Program. Given the recent installation of the ACS, there will be significantly fewer WFPC2 observations during this cycle, and as a result, the Cycle 11 calibration plan will be scaled back somewhat. However it will retain the same calibration accuracies for the modes being used by cycle 11 observers. This calibration program will also be developed with a view towards closure calibrations for WFPC2.

We plan to continue, with some modifications, most of the basic calibrations such as the decontaminations, photometric monitors, internal monitors, and observations needed for creating calibration files, such as weekly darks, biases, internal flats, and earthflats. A small number of orbits will also be dedicated for special calibration projects.

We invite the HST user community to provide suggestions for additional WFPC2 calibration observations that are currently unavailable or inadequate, and which can be expected to serve a significant fraction of WFPC2 users. Suggestions for calibration programs in Cycle 11 will be accepted until April 15th. These should also include details of the suggested exposures and estimates of the telescope resources (orbits) required. Please send your suggestions to Shireen Gonzaga (shireen@stsci.edu).

While your suggestions will be carefully considered against other necessary calibrations, the WFPC2 team cannot guarantee that it will become part of the final Cycle 11 Calibration Program.

Please be aware that there will also be an opportunity to submit Calibration Outsourcing proposals as part of the Cycle 12 GO program; the Calibration Outsourcing information that was made available during the previous Cycle 11 call for proposals is online at the WFPC2 Website.

WFPC2 Resumes Normal Operations After Servicing Mission 3B:

by A. M. Koekemoer and the WFPC2 Group

WFPC2 was cooled down to its normal operating temperature of -88C on Saturday 23 March, after having remained inactive during the servicing mission and the following two weeks, to help eliminate the risk of excessive contamination buildup on its CCD windows. A carefully designed, intensive program of UV contamination monitoring has been executed, starting immediately after cooldown, and results from these observations to date indicate that the decrease in throughput remains well within safe limits, being only moderately higher than the typical rates that are generally observed. More frequent decontaminations will be carried out during the first month of operations to ensure that the overall level of contamination remains within normal values.

We have also carried out preliminary analysis of other observations to verify the general performance of WFPC2, and our results to date indicate that there have been no major changes in its characteristics since before the servicing mission. The photometric throughput across a wide range of filters remains nominal (to within our measurement precision of a few percent), and thus far are consistent with the well-characterized long-term behaviour of the instrument. The image quality is nominal, after accounting for the current thermal state of the telescope. Results from the internal monitoring program, including darks and biases, suggest no major changes in the camera electronics since the servicing mission.

We are continuing a program of calibration observations aimed at improving the precision with which we may be able to characterize any smaller changes, as well as allowing us to continue monitoring well-known long-term trends in the behaviour of the instrument. These programs include a photometric sweep with the most commonly used filters, more detailed characterization of the UV throughput, along with new PSF, flatfield and internal calibrations. The results from these calibration programs will become available within the next two months, and will be applicable to all observations obtained after the servicing mission.

Updated WFPC2 Flatfield Reference Files for 1995 - 2001 (ISR 01-07):

by A. M. Koekemoer, J. Biretta & J. Mack

We present updated flatfields for the full set of 32 WFPC2 standard optical filters, redward of F300W, using on-orbit data from Earthflat exposures covering dates ranging from September 1995 - May 2001. We divide the flatfields into epochs depending on the appearance of major new features, thereby substantially diminishing the effect of such features on the data by calibrating their variation with time. We also quantify their wavelength dependence by examining Earthflats from a wide range of filters, and measure the time dependence of large-scale flatfield features that may be caused by long-term changes in the camera geometry. In addition, we are able to measure pixel-to-pixel structure to levels below ~0.3% for the PC and ~0.2% for the WF chips. Here we describe the procedures for creating the new flats, which are now available in the standard CDBS processing pipeline as updated WFPC2 calibration reference files.

Calibration Workshop Notice:

        The 2002 Hubble Space Telescope Calibration Workshop 
                        October 17-18, 2002 
                Space Telescope Science Institute                           

Charge-transfer efficiency, pedestal effects, point-spread functions, instrumental throughputs, scattered light, line-spread functions, cosmic-rays....whether we like it or not, the astronomical knowledge that will appear in tomorrow's textbooks hinges on understanding our sometimes imperfect sensory apparatus. In addition, pushing the forefronts of science often means pushing the instruments to their limits, where all kinds of calibration "gotchas" may be hiding.

So, come help set the course of astronomical history at the fourth HST Calibration Workshop. The workshop will feature reports from the commissioning of ACS and the re-commissioning of the NICMOS. New calibrations and advances in the understanding of STIS, WFPC2, FOS, GHRS, FOC, and the FGS will also be presented, as will previews of calibration plans for COS and WFC3 which are scheduled to be launched in two years. The workshop is intended to foster sharing of information and techniques between observers, instrument developers, and instrument support teams. There will be sessions of talks, posters, and time for demos or splinter groups on various topics.

The meeting will be held at the Space Telescope Science Institute, and will immediately follow the Astronomical Data Analysis Software & Systems conference being held in downtown Baltimore earlier the same week. The proceedings of the meeting will be published.

Further information on the workshop, including a pointer to a WWW site that will provide registration forms and instructions for presentations, will appear soon on the STScI HST web site, and will be advertised in future STANs (our electronic instrument newsletters).

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.

CELIS, S.L. "Imagenes HST de Gigantes Oscuros Como
Materia Oscura: Parte 1. Las Estrellas Capullos
Negros de la Region Nebulosa Carina = HST Images of
Dark Giants as Dark Matter: Part 1. The Black
Cocoon Stars of Carina Nebula Region" Nucleotecnica
21(35): 11-38, 2001

DROZDOVSKY, I.O.; SCHULTE-LADBECK, R.E.; HOPP, U.;
GREGGIO, L.; CRONE, M. "NGC6789: the Closest BCD
Galaxy Resolved with HST" Dwarf Galaxies and Their
Environment 95-98, 2001

DROZDOVSKY, I.O.; SCHULTE-LADBECK, R.E.; HOPP, U.;
GREGGIO, L.; CRONE, M. "The Nearby Starforming
Dwarf Galaxy NGC 4214" Dwarf Galaxies and Their
Environment 107-110, 2001

HEBER, U.; MOEHLER, S.; NAPIWOTZKI, R.; THEJLL, P.;
GREEN, E.M. "Resolving Subdwarf B Stars in Binaries
by HST Imaging" A&A 383: 938-951, 2002

IZOTOV, Y.I.; THUAN, T.X. "Hubble Space Telescope
Observations of the Cometary Blue Compact Dwarf
Galaxy UGC 4483: a Relatively Young Galaxy?" ApJ
567: 875-891, 2002

KENNEY, J.D.P.; YALE, E.E. "Hubble Space Telescope
Imaging of Bipolar Nuclear Shells in the Disturbed
Virgo Cluster Galaxy NGC 4438" ApJ 567: 865-874,
2002

LARSEN, S.S.; EFREMOV, Y.N.; ELMEGREEN, B.G.;
ALFARO, E.J.; BATTINELLI, P.; HODGE, P.W.;
RICHTLER, T. "Hubble Space Telescope Imaging of a
Peculiar Stellar Complex in NGC 6946" ApJ 567:
896-914, 2002

NOLL, K.; STEPHENS, D.; GRUNDY, W.; SPENCER, J.;
MILLIS, R.; BUIE, M.; CRUIKSHANK, D.; TEGLER, S.;
ROMANISHIN, W. "2000 CF_105" IAUC 7857: 1, 2002

SABBI, E.; ALOISI, A.; BELLAZZINI, M.; GREGGIO, L.;
LEITHERER, C.; MONTEGRIFFO, P.; TOSI, M. "The
Stellar Populations in NGC 1705" Dwarf Galaxies and
Their Environment 99-102, 2001

SARAJEDINI, A.; GREBEL, E.K.; DOLPHIN, A.E.;
SEITZER, P.; GEISLER, D.; GUHATHAKURTA, P.; HODGE,
P.W.; KARACHENTSEV, I.D.; KARACHENTSEVA, V.E.;
SHARINA, M.E. "The Stellar Populations of the Cetus
Dwarf Spheroidal Galaxy" ApJ 567: 915-921, 2002

SOLLERMAN, J.; FLYCKT, V. "The Crab Pulsar and Its
Environment" ESO Messenger 107: 32-35, 2002

CRONE, M.M.; SCHULTE-LADBECK, R.E.; GREGGIO, L.;
HOPP, U. "The Star Formation History of the Blue
Compact Dwarf Galaxy UGCA 290" ApJ 567: 258-276,
2002

DOHM-PALMER, R.C.; SKILLMAN, E.D.; MATEO, M.; SAHA,
A.; DOLPHIN, A.; TOLSTOY, E.; GALLAGHER, J.S.;
COLE, A.A. "Deep Hubble Space Telescope Imaging of
Sextans A. I. The Spatially Resolved Recent Star
Formation History" AJ 123: 813-831, 2002

DRESSEL, L.; GALLAGHER, J.S. "Structure and Gas
Dynamics in the Central 100 pc of a Powerful LINER
Galaxy" Central Kiloparsec of Starburts and AGN
298-301, 2001

GERSSEN, J.; VAN DER MAREL, R.P.; AXON, D.J.;
MIHOS, C.; HERNQUIST, L.; BARNES, J.E. "HST
Observations of NGC 6240" Central Kiloparsec of
Starbursts and AGN 665-671, 2001

KARACHENTSEV, I.D.; DOLPHIN, A.E.; GEISLER, D.;
GREBEL, E.K.; GUHATHAKURTA, P.; HODGE, P.W.;
KARACHENTSEVA, V.E.; SARAJEDINI, A.; SEITZER, P.;
SHARINA, M.E. "The M81 Group of Galaxies: New
Distances, Kinematics and Structure" A&A 383:
125-136, 2002

KENNEY, J.D.P. "HST Imaging of Bipolar Nuclear
Shells in the Disturbed Virgo Cluster Galaxy NGC
4438" Central Kiloparsec of Starbursts and AGN
133-139, 2001

LAINE, S.; VAN DER MAREL, R.P.; BOKER, T.; MIHOS,
J.C.; HIBBARD, J.E.; ZABLUDOFF, A.I. "HST
Observations of the Nuclear Regions of the Toomre
Sequence of Merging Galaxies" Central Kiloparsec of
Starbursts and AGN 179-182, 2001

LEVENSON, N.A.; CID FERNANDES, R.; WEAVER, K.A.;
HECKMAN, T.M.; STORCHI-BERGMANN, T. "AGN-Obscuring
Starbursts" Central Kiloparsec of Starbursts and
AGN 418-424, 2001

NELSON, A.E.; SIMARD, L.; ZARITSKY, D.; DALCANTON,
J.J.; GONZALEZ, A.H. "Constraints on the Size
Evolution of Brightest Cluster Galaxies" ApJ 567:
144-154, 2002

NISHIURA, S.; SHIOYA, Y.; MURAYAMA, T.; SATO, Y.;
NAGAO, T.; TANIGUCHI, Y.; SANDERS, D.B. "A
Multi-band Photometric Study of Tidal Debris in a
Compact Group of Galaxies: Seyfert's Sextet" PASJ
54: 21-32, 2002

ROMANIELLO, M.; PANAGIA, N.; SCUDERI, S.; KIRSHNER,
R.P. "Accurate Stellar Population Studies from
Multiband Photometric Observations" AJ 123:
915-940, 2002

SCHALLER, E.L.; FESEN, R.A. "The Nature of [Ar
III]-Bright Knots in the Crab Nebula" AJ 123:
941-947, 2002

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: www.stsci.edu/public/propinfo.html.

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

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