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WFC3 Post-Observations Ground System Design. M. Giavalisco H. Bushouse W.King. Introduction. Purpose : Obtain and manipulate all WFC3 SI data from observations through final storage and dissemination to the observer Process data through steps of : Generic conversion (OPUS)

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wfc3 post observations ground system design

WFC3 Post-Observations Ground System Design

M. Giavalisco

H. Bushouse

W.King

WFC3 IPT PDR

introduction
Introduction
  • Purpose : Obtain and manipulate all WFC3 SI data from observations through final storage and dissemination to the observer

Process data through steps of :

  • Generic conversion (OPUS)
  • Data reduction and Calibration (CALWF3)
  • Associations (CALWF3)
  • Archiving (DADS)

WFC3 PDR

wfc3 layout
WFC3 Layout

WFC3 PDR

wfc3 detectors
UVIS Channel

2 2k x 4k EEV Marconi CCDs

200 – 1000 nm

High QE

15 micron pixel

0.04 arcsec/pix

FOV 160 x 160 arcsec

IR Channel

1k x 1k HgCdTe array

850 1700 nm

High QE

18 micron pixel

Scale 0.13 arcsec/pix

FOV 123 x 139 arcsec

WFC3 Detectors

WFC3 PDR

slide7

WFC3 Pipeline

Routine Science Data Processing

Ref

files

Cal

files

Engineering

MISSION

SCHEDULE

headers

Associations

CALWFC3 SOFTWARE

Archive

  • Assembles data from WFC3 into scientifically useful data sets.
  • Processes the science data using standard calibration tools and reference files.
  • Calculates error arrays.
  • Stores raw data sets in the Archive.
  • Offline Tools/files for Observers to re-calibrate.

WFC3 PDR

design guiding principles
Design Guiding Principles
  • Maximize Reuse of ACS and NICMOS Pipelines
  • Treat UVIS and IR channels as similarly as possible
  • Leverage on the experience from and solutions adopted for WFPC2, NICMOS, STIS, ACS
  • Incorporate DRIZZLING to enhance effective spatial resolution, remove geometric distortions

WFC3 PDR

calwfc3 structure
CALWFC3 Structure
  • Use ACS structure for pipeline backbone: CALWF3 built from ACSCCD, ACS2D, ACSREJ.
  • Replace MAMA branch with CALNICA for IR channel.
  • Implement (minor) modifications and upgrades when required by lack of specific capabilities of ACS’s pipeline.

WFC3 PDR

major pipeline building steps
Major Pipeline Building Steps
  • 1) Required changes for reuse of ACS/NICMOS pipelines:
    • 1.1) Flatfield implementation (due to geometric distorsions)
    • 1.2) IR subarrays (UVIS is a copy of ACS WFC)
    • 1.3) IR overscan pixels (UVIS overscan pixels - built into ACS pipeline)
    • 1.4) Binning (currently removed from ACS pipeline, but straightforward to replace)
    • 1.5) Associations - use ACS as baseline
    • 1.6) WFC3 Keywords (based on ACS and NICMOS)
    • 1.7) Adopt future NICMOS and ACS science upgrades, as applicable

WFC3 PDR

1 1 flatfield implementation
1.1 Flatfield Implementation
  • Build capabilities in the SW to handle different type of flat fields (pix-to-pix, delta-flat, low-frequency, etc.), as needed for WFC3
  • Account for the effect of geometric distortions during flat fielding operation (due to variations in pixel area)

WFC3 PDR

1 2 subarrays
1.2 Subarrays
  • Must use IR subarrays for photometric calibrations of NICMOS standards
  • UVIS subarrays to follow ACS model : center, size variable in parallel direction
  • IR subarrays to be of size 512,256,128,64,32 on a side, centered on middle of array
  • Enable the NICMOS SW to handle OVERSCAN pixels
  • Must be able to correct for geometric distortions for different size/position subarrays
  • Must handle relevant calibrations for specific size/position subarrays

WFC3 PDR

1 3 overscan pixels
1.3 Overscan Pixels
  • Both physical (to remove bias effects) and virtual (to remove amplifier effects) overscan for UVIS - use ACS solutions
  • Physical overscan (“reference”) pixels only for IR
  • Used to remove itinerant baselines, biases varying by quadrant, amplifier
  • Necessary to avoid corruption of edge pixels if binned; DQI flag to be set to acknowledge this (no problem if binning is 1x,2x,3x, and OVSC size is multiple of these numbers)

WFC3 PDR

1 4 binning
1.4 Binning
  • Needs to be put back into ACS pipeline
  • Implemented via binned reference files
  • Will support 2x2, 3x3 for UVIS
  • Prevent mixing of overscan and “good” edge pixels => set DQI flag

WFC3 PDR

1 5 associations
1.5 Associations
  • Inputs will follow ACS example: science imsets from CALWF3, pixel shift from jitter file/guide star system, “pixel fraction”, pixel weight (bad mask) file
  • The implementation of DRIZZLING will associate dithered images, no mosaics
  • DRIZZLING can also do 2 UVIS imsets => 1 UVIS image, geometric distortion corrections as well

WFC3 PDR

1 6 wfc3 keywords
1.6 WFC3 Keywords
  • Reuse ACS, NICMOS keyword sets
  • Keep separate set of keywords for UVIS, IR channels
  • Resolve contradictions in definitions using ACS conventions
  • Keep only critical engineering snapshot keywords (about NICMOS) in science headers, remainder in .SPT headers for monthly trending of other engineering keywords

WFC3 PDR

1 7 nicmos science upgrades
1.7 NICMOS Science Upgrades
  • The pipeline will incorporate the improved CR rejection algorithms (proper treatment of correlated errors)
  • The upgrades Wwll be meshed with improvements in WFC3 MUX, detector design to track systematics

WFC3 PDR

major pipeline building steps1
Major Pipeline Building Steps
  • 2) Desired changes for improved CALWF3 pipeline
  • 2.1) Specific dithering strategies for DRIZZLING implementation -> dither patterns
  • 2.2) Geometric distortions corrections: e.g. DRIZZLING, but other options possible- (will monitor ACS solutions/progress)
  • 2.3) Adopt optimized CR rejection strategies, either with CR-REJECT or during DRIZZLING (will monitor ACS solutions/progress)

WFC3 PDR

2 2 drizzling dithering strategies
2.2 DRIZZLING & Dithering Strategies
  • DRIZZLING will improve angular resolution (but make error analysis more complicated)
  • Allow either standard TRANS line, box/spiral patterns, or custom ones
  • DRIZZLING can also paste together two halves of UVIS image

WFC3 PDR

2 3 geometric distortions
2.3 Geometric Distortions
  • Expected geometric distortion (~10% across the WFC3 FOV)
  • Need to correct for registration and calibration, and when taking calibrations for the different modes of the instrument.
  • Need to account for geometric distorsion effects to properly flat-field point vs. extended sources
  • Correction done in CALWF3 using DRIZZLING
  • Cubic polynomial description in X,Y w/ cross-terms
  • Coefficients kept in IDC, SIAF files

WFC3 PDR

conclusions
Conclusions

WFC3 Pipeline Will :

  • Take raw instrument science data and convert it into FITS files suitable for science analysis
  • It will support WFC3 Thermal Vacuum ground testing and verification at NASA/GSFC
  • Take advantage of maximal reuse of ACS and NICMOS pipelines.
  • It will build on ACS pipeline structure with CALNICA replacing the MAMA code, including DRIZZLING

WFC3 PDR