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WFPC2 Closeout Plan
John Biretta 25 Oct 2006


WFPC2 Legacy
· Large fraction of HST output. · Currently ~40% of HST post-repair orbits (prime, parallels, ext cals). · By SM4: ~14 years on-orbit and ~120,000 science images.

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Goals of Remaining WFPC2 Support
· Primary goal: ensure future archival users can readily obtain accurate results from WFPC2. · Correct known calibration issues where possible. · Document remaining known deficiencies. · Make well-calibrated data easy to obtain. · Minimize / eliminate need for manual user calibrations. · Continue operating and calibrating WFPC2 up to SM4.

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Priorities
· · · · Keep WFPC2 operating as well as possible to SM4. Perform routine calibrations as previously done. Document known issues. Attempt to solve technical calibration issues while WFPC2 expertise exists. · Make calibration easier for archival users, where possible. · Defer most archive specific work (e.g. static archive) to future. · Projects prioritized as committed / high / medium.

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Specific Areas & Potential Projects
· · · · · · · · · · · Routine monitors and calibrations. Special closeout observations. WF4 anomaly. CTE studies. HST global photometric accuracy. Improve photometric zeropoints. Low light flats for broadband filters. Red-leaks in blue and UV filters. Narrowband and ramp filters. Documentation. User support / management / etc.
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Routine Monitors and Calibrations
· Basic calibration observations to support on-going GO observations and special close-out programs. · DECONs, biases, darks, flats, photometry data. · Perform basic analyses ­ make bias and dark reference files, populate photometric monitor tables, measure CTE. · Committed to do. 21 orbits. 0.7 FTE yrs.

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Special Closeout Observations
· Special end-of-mission observations to enhance calibration. · Topics addressed: CTE (background dependency, extended targets), low-light broad band flats, photometric zeropoints, red leaks, red filters, ramp & narrow band filters, polarizers, geometric distortion. · Detailed plan at WFPC2 website
http://www.stsci.edu/hst/wfpc2/analysis/WFPC2_cyc1516_cal_plan_final.pdf

· Committed to write proposals and take data. · 68 orbits. 0.3 FTE yrs. · Analysis work discussed separately....

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WF4 Anomaly
· · · · · · · · · · · Monitor health of WF4 Keep WF4 functioning: Perform temperature adjustment in Jan. 2007, possibly also Aug, 2007. Document work on temperature adjustments & their impact. Derive and document photometric corrections. Impacts ~20% of images by numbers; science impact 6%? Has indirect impact on many areas of calibration. Committed to do. 0.5 FTE yr. Software tasks to correct photometry and background streaks. Pipeline-based corrections. Requires work from software / pipeline groups. High priority. 0.3 FTE yr.

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CTE Studies
· CTE is greatest single lien on WFPC2 data quality, accuracy, and ease of use. · Existing CTE correction equations derived prior to 2002. Re-derive corrections for entire mission. · Simplify CTE corrections ­ currently 3 sets of corrections that often give different results. · Image based corrections? Greatly simplify future archival use / improve accuracy if corrections were made in pipeline. Valuable asset for other instruments ­ WFPC2 good test bed ­ long history and large CTE. · Impacts ~80% of data to some degree. · High priority; 0.6 FTE yr.

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HST Global Photometric Accuracy
· · · · Compare photometric scales of past / current instruments. Study long-term trends in HST throughput (especially UV). WFPC2 has 14 year overlap with other instruments. Medium priority; 0.2 FTE yr.

Improve Photometric Zeropoints
· · · · Accurac Analyze Impacts Medium y ~2% in visual and red; only 3% to 4% in blue. additional standards & standard fields. ~45% of images. priority; 0.3 FTE yr.

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Low Light Flats for Broadband Filters
· Existing broadband filter flats are combination of ground test data and on-orbit illumination corrections derived from narrow-band filters. · Directly derive flats for broadband filters: · Sky flats: large archive of images available. · Full moon Earth flats: earth illuminated by full moon provides correct brightness for direct broadband flats. (Effort needed from scheduling group.) · Impacts ~94% of images. · Medium priority; 0.4 FTE yr.

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Red-Leaks in Blue and UV Filters
· · · · Red-leaks not well calibrated on-orbit. Evaluate spatial variations and any long-term changes. Impacts ~35% of images. Medium priority; 0.2 FTE yr.

Narrow Band and Ramp Filters
· Possibility that filters change in space environment due to chemistry processes. · Evaluate central wavelengths, band widths, throughputs. · Some evidence for 5% - 10% photometry errors in ramps. · Impacts ~4% of images. · Medium priority; 0.5 FTE yr.

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Documentation
· Instrument Handbook final version. Last full version 2004; only short updates since then. · Data Handbook final version. Current version is Jan. 2002. · Website Clean-up. Convert from "work in progress" to "final document." Remove out-of-date / redundant / wrong material. Improve accessibility and usability. Sensible paths to material vs. historical accidents. · Summary document "The WFPC2 Experience." Single document summarizing history and issues from archival user point-of-view. · High + medium priority tasks; 0.4 + 0.4 FTE yr.

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Miscellaneous Items
User support · Proposal reviews, help desk, etc. · High priority. 0.1 FTE yr. Management · Closeout planning, presentations, meetings. · Committed to do. 0.2 FTE yr. Contingency · Unexpected events, training new staff, SM4 delays, etc. · 1 FTE yr.

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Final Thoughts
· Projects outlined herein should be thought of as "potential" projects. · Current WFPC2 staffing adequate to accomplish most of the "committed" projects ­ primarily operating WFPC2 until SM4. · High and medium priority projects will require up-staffing WFPC2 group or outsourcing. · Total effort in all projects is similar to past closeouts, but may be difficult to support concurrently with SM4, etc.

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STUC Input Welcomed
· Are priorities correct? · Suggest additional projects? · Outsource some projects?

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