HST Mission - Standard Operations WFPC2 Reprocessing NICMOS Reprocessing

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1 HST Mission - Standard Operations WFPC2 Reprocessing NICMOS Reprocessing Helmut Jenkner Space Telescope Users Committee Meeting 13 November 2008

2 WFPC2 Reprocessing As part of the WFPC2 decommissioning effort, we have undertaken two major projects: Implementation of calibration and software enhancements to the CALWP2 pipeline. Using this new pipeline, reprocessing of the entire WFPC2 data set into a static archive of calibrated data. Once reprocessing is complete, all requests for WFPC2 data will be fulfilled from the static archive. On-the-fly reprocessing (OTFR) will be discontinued for WFPC2. 13 NOV 2008 STUC 2

3 WFPC2 Pipeline Improvements Correction for WF4 bias anomaly. New flat-field, bias, and dark reference files for area-mode images (binned 2x2). New header keywords (CTE_1E2, CTE_1E3, CTE_1E4) to track flux lost to CTE effects. Improved zero-point and throughput calibrations for a variety of filters. A new keyword (ZP_CORR) to correct for UV contamination and temporal variations in QE. Improved, time-dependent corrections for geometric distortion, chip-to chip drift, and the 34th-row error. The Simple Imaging Polynomial (SIP) convention is used to store distortion information in the FITS image headers. New product: a combined 4-chip quick-look image for each observation (from PyDrizzle). Calibrated images available in both Multi-Extension FITS (MEF) and Waiver FITS (wfits) formats. 13 NOV 2008 STUC 3

4 Chip drift: temporal variations in the X (top) and Y (bottom) positions of the PC, WF2, and WF4 chips relative to WF3; units are WF3 pixels. 13 NOV 2008 STUC 4

5 Schedule and Status Reprocessing began on 16 October Work done in chronological order, but postpone data taken: before 24 April 1993 (temperature change), after March 2002 (WF4 anomaly), through multiple filters, in area mode, through narrow, ramp, and polarized filters. About 15% of the 180,000 WFPC2 images have been reprocessed to date. Should finish bulk of images in March Reprocessing will continue until approximately 3 months after SM4. 13 NOV 2008 STUC 5

6 Quality Control Trailer files for all images are scanned for error and warning messages. From each day s images, half a dozen are retrieved from the static archive; header keywords are checked and quick-look images examined. The pipeline is modified to correct any anomalies. Images are identified for re-reprocessing (2721 to date). 13 NOV 2008 STUC 6

7 Documentation A STAN describing pipeline enhancements and plans for reprocessing was distributed last week. A web page with the same information has been added to the WFPC2 web site. MAST maintains a WFPC2 reprocessing status page. A final version of the WFPC2 Instrument Handbook was released in August, and a final version of the Data Handbook will be published in the spring. Reports on the various calibration efforts (WF4 anomaly, geometric distortion, etc.) are also in preparation. 13 NOV 2008 STUC 7

8 NICMOS Legacy/Closeout Reprocessing Expanded Cycle 16/17 calibration programs: Include full temperature dependence: Flatfields. Darks: amplifier glow, linear dark, electronic shading. Improved photometric non-linearity & cross-calibration. Improved grism dispersion, zeropoints, spectrophot. Reprocessing: Improved calibration software incorporated into OPUS: SAAclean: removal of SAA CR persistence. Bright Earth persistence removal. Temperature from bias. Calnica: improved CR/bad pixels, error arrays. Staypuft: removal of electronic crosstalk ghosts. Rnlincor: Count-rate-dependent non-linearity. Post-OPUS HLA reprocessing: Improved low-level / pedestal background correction. MultiDrizzle image combination. 13 NOV 2008 STUC 8

9 New Temperature-Dependent Darks and Flats Full temperature-dependent recalibration of darks and flats: Covers pre-ncs as well as post-ncs data. Can potentially remove existing low-level artifacts that are the result of temperature variations. New reference files created and delivered to OPUS Amp glow signal Ratio between pipeline flats and temp-dependent flats from the monitoring program (NIC1/F160W). For a change in temp-from-bias by ΔT~2K, the measured signal of the NIC 3 amp glow changes by ~1%. This is sufficiently large to impact calibrations, in particular this affects There is a clear change in flat-field the corners of the images where the amp glow effect is the largest. structure caused by the change in temperature. 13 NOV 2008 STUC 9

10 NICMOS detector effects - correctable with reprocessing SAA-impacted CR persistence Original image SAA model Cleaned image Electronic ghosts ( mr. Staypuft ) Electronic shading Supershading Bright object persistence 13 NOV 2008 STUC 10

11 Temperature-from-bias The problem: Solution: NICMOS highly temp-sensitive. The mounting cup temps do not measure actual detector temp. Use detector as diode to measure temperature. May be possible to measure temp to 5-10mK when including voltage effects. Bright Earth persistence removal Before After Count-rate non-linearity correction: Before After 13 NOV 2008 STUC 11

12 Data Reprocessing Plan / Timeline (1) Part A: Archive / OPUS recalibration (~Dec 2008): Create a final, static, recalibrated set of all NICMOS exposures. Run temp-from-bias on all NICMOS data: Populate header keywords for each image, used in subsequent processing. New calnica: Apply new temperature-dependent dark files to all NICMOS data: Amplifier glow, linear dark. Electronic shading. Apply new temperature-dependent flats to all NICMOS data. Run SAAclean, staypuft, bright earth persistence on affected datasets. 13 NOV 2008 STUC 12

13 Data Reprocessing Plan / Timeline (2) Part B: Higher-level processing with HLA (~Jan/Feb 2009): Apply low-level background / pedestal removal: Likely robust enough to be run on all NICMOS exposures, but requires data quality inspection to verify. Run MultiDrizzle to create combined drizzled exposures: Start with data that benefit from drizzling (well-dithered, sufficient exposures). May extend to other datasets, pending data quality / validation. 13 NOV 2008 STUC 13