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Hubble Space Telescope
WFPC2 STAN

S T A N / W F P C 2 - Number 36, June 1999

CONTENTS:

WFPC2 Instrument Handbook Update Available:

by S. Casertano and the WFPC2 Group

A new update to the WFPC2 Instrument Handbook has been released, replacing the previous update. The update focuses on the latest information on photometric anomalies, both CTE and long vs. short, and on new results concerning the long-term stability of the photometric response of WFPC2. It also includes updates on the PSF properties, the known variations in aperture corrections vs. focus and field position, and on the WFPC2 dark current, which has increased significantly since WFPC2's installation. We report on the latest improvements on the Drizzle software to reconstruct dithered images, and on the current and future WFPC2 calibration plans.

Corrections for the 34th Row Effect:

A correction for the 34th row effect in WFPC2 images is described in a paper by J. Anderson and I. R. King, recently accepted for publication in the PASP. With the authors' permission, the paper has been made available on the WFPC2 Documentation Webpage.

The abstract reads:

A small manufacturing defect, known but rarely noted, occurs at approximately every 34th row of each of the chips of WFPC2. This defect induces systematic errors in photometry at the 0.01-0.02 mag level for about 6% of all stars, and periodic errors in astrometry for all stars, with an amplitude of 0.03 pixel. We derive simple corrections for these errors. The errors exist in all astrometry and photometry previously done with WFPC2, but they can be avoided in future work by applying the corrections that we give here.

WFPC2 AAS Posters Available Online:

The WFPC2 posters presented at the June '99 AAS meeting in Chicago are now available online in the WFPC2 Documentation Webpage.

Wide-Field Planetary Camera II Status Update:

by J. Biretta, S. Baggett, S. Casertano, S. Gonzaga, I. Heyer, M. S. Wiggs, M. McMaster

Abstract: We review the status of the Wide-Field Planetary Camera II (WFPC2) onboard the Hubble Space Telescope as well as recent enhancements to calibration and analysis methods. The instrument continues to perform extremely well. Low level effects such as dark current and CTE continue to increase with long-term radiation exposure (see poster on CTE by Heyer et al.), but have minimal effect on most observations. The long-term photometric stability appears to be excellent, with most filters showing changes of a few percent or less. Recent work shows that aperture photometry for small apertures (1-2 pixel radius) will be affected at the 5% to 10% level by target position due to small focus variations across the CCD. New flat fields are available which correct long-term changes in the illumination pattern; corrections are typically 0.5%, though small dust spots have corrections up to 12%. The Dither Package software has been upgraded to include mosaicing of all 4 CCDs, as well as cosmic ray removal from single image pointings. These and other topics are reviewed.

Charge Transfer Efficiency of the Wide Field and Planetary Camera 2

by I. Heyer, B. Whitmore, S. Casertano, J. Biretta

Abstract: Observations of omega Cen have been used to characterize the Charge Transfer Efficiency (CTE) of the Wide Field and Planetary Camera 2 (WFPC2) onboard the Hubble Space Telescope. A set of formulae has been developed to correct for CTE loss, with dependencies on the X and Y positions, the background counts, the brightness of the star, and the time of the observation. The observations indicate that for very faint stars on a very faint background, the CTE loss from the top to the bottom of a chip has increased from about 4% shortly after the cool-down of WFPC2 (April 23, 1994) to roughly 40% in February 1999, presumably as a result of radiation damage in the space environment. In general, typical WFPC2 exposures are much longer than these short calibration images, resulting in higher background which significantly reduces the CTE loss and minimizes the CTE problem for most science exposures.

Paper Products in Electronic Format:

by D. Christian and the HST Archive Branch

The archive branch, in an effort to save resources, is planning to provide DADS paper products in electronic format only. Paper product content remains the same, but paper products are now converted into Adobe Portable Document format (PDF). As done previously, PDF files summarize the observations made by a particular observer during one "Science Mission Schedule" (i.e., SMS) week. The PDF files must be viewed using the ADOBE Acrobat Reader, which can be obtained from our page if it's not currently available from your WEB browser.

Users have several options with which to search for PDF files, including: proposal number, PI last name, target name, data set name and observation date. Help is available on the possible search fields. Files are password protected (unless the proposal is a calibration program) and users will need their archive name and password to access documents. This interface is not intended for general archive users but specifically for PIs of HST programs. The archive plans to stop printing paper products on August 1, but will still provide paper hard copies in case of special need.

Please direct any comments or questions to archive@stsci.edu.

Last Call: Filter Workshop in July for Wide Field Camera 3

The STScI and the WFC3 Science Oversight Committee are hosting a one-day WFC3 Filter Workshop at the Space Telescope Science Institute on July 14, 1999 where we hope to collect the advice and recommendations of the community concerning the filter selection. We are taking this opportunity to alert the community of the workshop and encourage all that are interested in participating to visit the WFC3 website for further details.

Please note that there have been numerous additions to the website since our announcement in the last WFPC2 STAN. In particular, we draw your attention to the discussion board and voting page for WF3 filters; any suggestions or comments would be most welcome.

Job Opening: WFPC2 Instrument Scientist (Scientific Fixed-Term Appointment):

The Space Telescope Science Institute currently has an opening for the position of WFPC2 Instrument Scientist. Working under the supervision of the Lead of the WFPC2 Group in the Science Support Division (SSD), the incumbent will actively support the WFPC2 science program and participate in the calibration, monitoring, and technical support of the instrument. Work also includes updating the user documentation and WWW pages related to WFPC2. The individual will also be responsible for providing direct support to WFPC2 proposers, observers, and archival users. He/she will be supported in his/her work by Data Analysts in the WFPC2 Group, and may be responsible for overseeing their work.

This position is a scientific fixed-term appointment with a duration of two years, with the possibility of renewal for a third year. An average of between 20% and 50% of the regular working hours will be available for independent scientific research, depending on the qualifications of the candidate; additional science time, up to the limit of 50% of the regular working hours may be reimbursed from independent grants.

Applicants must possess a Ph.D. in astronomy or physics, with at least three years of experience at the post-doctoral level. Experience with imaging data for scientific analysis or calibration is desirable. Experience with HST in general, and WFPC2 in particular, is highly desirable. Candidates must have familiarity with IRAF/STSDAS and the ability to generate clear and concise userdocumentation. Familiarity with IRAF/CL scripting and programming is desirable. Candidates should have the ability to work with a minimum of direction, enjoy research, possess skills to develop excellent working relationships, and be able to work effectively and collaboratively in a group. Candidates should send a cover letter with current curriculum vitae, list of publications, and the names of three references to:

                Human Resources Manager
                Space Telescope Science Institute
                3700 San Martin Drive
                Baltimore, MD 21218

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.

BOKER, T.; VAN DER MAREL, R.P.; VACCA, W.D.  "CO-Bandhead
Spectroscopy of IC 342: Mass and Age of the Nuclear Star
Cluster"  AJ 8-99

FERRARO, F.R.; PALTRINIERI, B.; ROOD, R.T.; DORMAN, B.
"Blue Straggler Stars: the Spectacular Population in M80"
ApJ accepted

SAHA, A.; SANDAGE, A.; TAMMANN, G.A.; LABHARDT, L.;
MACCHETTO, F.D.; PANAGIA, N.  "Cepheid Calibration of the
Peak Brightness of SNe Ia. IX. SN 1989B in NGC 3627"  ApJ
accepted

SCHULTE-LADBECK, R.E.; HOPP, U.; CRONE, M.M.; GREGGIO, L.
"A Stellar Population Gradient in VII Zw 403 - Implications
for the Formation of Blue Compact Dwarf Galaxies"

BIANCHI, L.; SCUDERI, S.  "Hot Massive Stars in Local Group
Galaxies"  Mem. Soc. Astron. Ital.

CHANDAR, R.; BIANCHI, L.; FORD, H.C.; SALASNICH, B.  "Star
Clusters in M33. III. The Youngest Population"

GILLILAND, R.L.; NUGENT, P.E.; PHILLIPS, M.M.  "High
Redshift Supernovae in the Hubble Deep Field"  ApJ 8-10-99

KISSLER-PATIG, M.; ASHMAN, K.M.; ZEPF, S.E.; FREEMAN, K.C.
"HST Imaging of Globular Clusters in the Edge-on Spiral
Galaxies NGC 4565 and NGC 5907"  AJ accepted

MCLURE, R.J.; KUKULA, M.J.; DUNLOP, J.S.; BAUM, S.A.;
O'DEA, C.P.; HUGHES, D.H.  "A Comparative HST Imaging Study
of the Host Galaxies of Radio-Quiet Quasars, Radio-Loud
Quasars and Radio Galaxies: Paper I"  MNRAS 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. 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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