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WFPC2 STAN

S T A N / W F P C 2 - Number 41, June 2000

CONTENTS:

Cycle 10 Call for Proposals/WFPC2 Outsourcing Candidates:

NASA and The Space Telescope Science Institute are pleased to announce the Cycle 10 Call for Proposals for astronomical observations and archival research utilizing the Hubble Space Telescope (HST). Participation in this program is open to all categories of organizations, both domestic and foreign, including educational institutions, profit and nonprofit organizations, NASA Centers, and other Government agencies. This solicitation will be open from June 14, 2000 through September 08, 2000 8:00pm EDT, and proposals may be submitted throughout this period. Results of the selection will be announced in mid to late December 2000.

Specific guidelines for proposal preparation are available electronically from the Space Telescope Science Institute's World-Wide Web site at the Cycle 10 Announcement Web Page.

All programmatic and/or technical information is available at the web site or you can contact the STScI Help Desk, at help@stsci.edu.

WFPC2 Outsourcing Candidates:

We also draw your attention to the new outsourcing possibilities for calibration projects. Outsourcing is an STScI initiative to fund external groups to perform and document some aspects of HST calibration. These funded groups would be contracted to analyze the calibration data and document the results, which would then be made available to the GO community by STScI. The projects to be outsourced could rely on archival data or could require obtaining new calibration data; the aim is not to replace the current calibrations but to complement and extend the current programs. Outsourcing proposals for Cycle 10 will follow the normal GO proposal process, requiring evaluation and approval by the TAC.

New Version of the WFPC2 Instrument Handbook:

-J. Biretta, I. Heyer, S. Baggett, S. Gonzaga, S. Casertano, A. Koekemoer, M. McMaster, C. O'Dea, A. Riess, A. Schultz, B. Whitmore, M. S. Wiggs

A major activity during the past two months has been a complete revision of the WFPC2 Handbook in preparation for Cycle 10. The last major revision of the Handbook was prior to Cycle 6 (version 4.0). Since that time we have provided only short update documents for each Cycle. The new version 5.0 incorporates material from those updates, as well as the following new material for Cycle 10:

	- Comparisons with ACS expected performance.
	- Updated focus history.
	- Aperture corrections as function of field position.
	- F1042M PSF anomaly.
	- Astrometry - new geometric corrections.
	- Fully revised throughput tables and filter throughput plots. 
	- Updated sample SNR calculations.
	- Long-term photometric stability.
	- CTE workshop results, and latest CTE time-dependence and
	  corrections.
	- Advice on current dither strategies.
	- Cycle 8 and 9 calibration plans.

Cycle 9 Calibration Plans:

-S. Baggett, S. Gonzaga, J. Biretta, S. Casertano, I. Heyer, A. Koekemoer, M. McMaster, C. O'Dea, A. Riess, A. Schultz, B. Whitmore, M. S. Wiggs

Calibration plans for Cycle 9 are being finalized and as always, observers are welcome to suggest new calibrations or comment on the existing plans (help@stsci.edu).

Abstract:

This report presents the details of the WFPC2 Cycle 9 calibration plans. The proposal suite is aimed at maintaining the calibration accuracy of WFPC2 via monitoring programs, as well as continuing some previous proposals into Cycle 9 and performing several new tests. The standard monitoring programs will be continued (e.g., decontaminations, photometric and astrometric monitors, darks, biases, internal flats, and Earth flats). In addition, the CTE monitor, PSF and photometric checks will be performed. Three new programs are planned as well: a red leak check, a verification of the wavelength stability of the narrowband and linear ramp filters, and a CTE calibration. The CTE calibration, in conjunction with WIYN groundbased observations, will permit a direct verification of the absolute photometric calibration of WFPC2 in observations that may be affected by CTE, providing a more robust determination of the zero point for many WFPC2 observations.

AAS Posters Available Online:

Two WFPC2 calibration posters were presented at the June 2000 AAS meeting; the abstracts are included below. The full posters can be viewed online, in postscript or PDF formats, at the WFCP2 Website:

Charge Transfer Efficiency in the WFPC2 CCD Arrays:

-J. Biretta, A. Riess, S. Baggett, B. Whitmore, S. Casertano, I. Heyer, A. Schultz, S Gonzaga, M. S. Wiggs, M. McMaster, C. O'Dea, A. Koekemoer (STScI)

We present an overview of Charge Transfer Efficiency (CTE) issues in the WFPC2 CCDs, including results of recent on-orbit tests, and advice on mitigating CTE effects on photometry. New studies using hotpixels, cosmic rays, and residual images as probes of CTE have revealed at least four distinct components of CTE losses. The largest effect appears related to trapping and release of charge on timescales of hundreds of milliseconds during the readout process. This is manifest as tails on images which extend for dozen of pixels in the Y-direction (parallel register direction) on the CCDs, which have the effect of robbing counts from typical small apertures used for photometry. There is considerable evidence now for a quasi-linear increase in CTE effects with time, due to on-going radiation damage to the CCD arrays in the harsh space environment. We review empirical results on stellar photometry, and preliminary results of new tests on extended targets (faint galaxies). We suggest observational strategies for reducing the impact of CTE, and photometric corrections which can be applied during data analysis.

Wide Field Planetary Camera II Status Update:

-M. S. Wiggs, J. Biretta, S. Baggett, S. Casertano, C. O Dea, A. Schultz, S. Gonzaga, I. Heyer, M. McMaster, A. Koekemoer, A. Riess (STScI)

We review the status of the Wide-Field Planetary Camera II (WFPC2) onboard the Hubble Space Telescope as well as summarize the re-commissioning tests performed after the December 1999 Servicing Mission (SM3a). While WFPC2 itself was not serviced, there is always concern about contamination or other unexpected effects. Although contamination rates increased during the mission (as expected), bi-weekly decontaminations immediately after SM3a, and subsequent monthly decons have successfully restored the UV throughput to their pre-SMOV values; there is no evidence of any permanent contamination. A photometric sweep covering the entire wavelength range of WFPC2 shows that any changes in the photometric response are less than ~1% at visible wavelengths, and less than 2% or 3% in the UV. No changes due to SM3a were seen in the flat field response, read noise, dark current, a-to-d gain ratios, and point spread function tests. In addition to the SM3a results, we also discuss the general status of WFPC2, including improved documentation for dithering, the now-public on-the-fly calibration (OTFC) of the archive, and plans for calibrating WFPC2 in Cycle 9. CTE results are presented in a separate poster.

MEETING NEWS:

Detector Workshop June 26-30, 2000 Space Astrophysics Detectors and Detector Technologies

Advances in detectors play a key role in the development of observational astrophysics. Looking towards the next decade of space missions, NASA's Office of Space Science wishes to bring together scientists and engineers working in areas ranging from gamma-rays to radio wavelengths to present the state-of-the-art in current and emerging detector technologies. The meeting will be of interest to detector developers and technologists as well as to scientists proposing new science missions.

Release of the Visual Target Tuner:

-Steve Lubow

With the June Call for Proposals, STScI will release a prototype software tool called the Visual Target Tuner (VTT). The VTT was originally developed as a proof of concept by a collaborating team from NASA Goddard and STScI (aaaprod.gsfc.nasa.gov/SEA). This tool displays HST apertures superimposed on sky images. The VTT provides capabilities to import sky images, display primary and parallel apertures, rotate apertures, centroid objects, specify excluded points and regions, experiment with various orientations, and display catalog overlays and object information. The tool can be useful for either Phase I or Phase II of HST proposal preparation, although its main use is likely to be for Phase II.

At present, the tool provides capabilities for analyzing fixed targets only. In Phase I, the tool can be used to answer questions such as: How many fields will I need to mosaic my extended target? Which of my potential targets "fits best" in the aperture? Is there anything interesting I can pick up with a coordinated parallel in another aperture? Do any of my potential targets have nearby bright objects that could spoil the observation? Is there an orientation which would avoid the bright object?

The VTT is supported for use on the Solaris and Windows operating systems. Further information about this tool will be available on the "Proposing to Use HST" Web page. If you think you would benefit from a tool like this in either Phase I or Phase II we encourage you to download and try the software. The feedback we receive this summer will play a role in determining our priorities for the Phase II release in December.

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.

MAURON, N.; HUGGINS, P.J. "Multiple Shells in
PRC+10216: Shell Properties" A&A accepted

STANGHELLINI, L.; SHAW, R.A.; BALICK, B.; BLADES,
J.C. "Large Magellanic Cloud Planetary Nebula
Morphology: Probing Stellar Populations and
Evolution" ApJ 534: L167-L171, 2000

DICKINSON, M. "Galaxy Formation at 0 < z < 2 from
the NICMOS HDF-North" Moriond Ap. Mtg. 19:

FERGUSON, A.M.N.; GALLAGHER, J.S.; WYSE, R.F.G. "On
the Nature of Andromeda IV" AJ accepted

DE KOFF, S.; BEST, P.; BAUM, S.A.; SPARKS, W.;
ROTTGERING, H.; MILEY, G.; GOLOMBEK, D.; MACCHETTO,
F.; MARTEL, A. "The Dust-Radio Connection in 3CR
Radio Galaxies" ApJS 6-00

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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