SPACE TELESCOPE SCIENCE INSTITUTE
TIPS: 21 February 2002
WFPC2
Anton Koekemoer
Wide Field and Planetary Camera 2
• WFPC2 News:
– New WFPC2 Group Lead: Brad Whitmore (as of January 1, 2002)
• New WFPC2 Documentation
• Cycle 11 WFPC2 Science Usage
• WFPC2 SM3B Plans
• WFPC2 Software Development
• Filter Wheel Rotation Anomaly
1
SPACE TELESCOPE SCIENCE INSTITUTE
TIPS: 21 February 2002
WFPC2
Anton Koekemoer
Recent WFPC2 Documentation
ISRs:
WFPC2-2001-09 The WFPC2 Photometric CTE Monitor
Heyer
WFPC2-2001-10 An Improved Geometric Solution for WFPC2
Casertano, Wiggs
WFPC2-2001-11 Summary of WFPC2 SM3B Plans
Koekemoer et al.
WFPC2-2002-01 WFPC2 Clocks-ON Close Out
Schultz et al.
WFPC2-2002-02 WFPC2 Flatfield Updates 1995 - 2001
Koekemoer et al.
HST Dither Handbook v2.0, Jan. 2002 (Koekemoer et al.)
WFPC2 Data Handbook v4.0, Feb. 2002 (Baggett & McMaster, Editors;
Mobasher, Chief Editor, HST Data Handbook)
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TIPS: 21 February 2002
WFPC2
Anton Koekemoer
SPACE TELESCOPE SCIENCE INSTITUTE
Cycle 11 WFPC2 Science Usage
Proposal ID
PI
Orbits
Filters
9354
Karkoschka
1
(Prime)
F225W,F336W,F410M,F467M,F588N,F673N,F953N,FQCH4N
9356
Zijlstra
60
(Prime/Snap)
F502N,F547M,F656N
9367
Hazard
22
(Prime)
F225W
9371
Chu
2
(Prime)
F555W,F675W,F814W
9385
Lemmon
2
(Prime)
F336W,F439W,F547M,F588N,F673N,FQCH4N
9393
Sromovsky
14
(Prime)
F225W,F336W,F410M,F467M,F547M,F588N,F631N,F673N,
F791W,F850LP,F935N,FQCH4N
9420
Davidson
6
(Prime)
F336W,F375N,F502N,F631N,F656N,F658N,F673N,F953N
9436
Kuijken
3
(Prime)
F814W
9461
Biretta
1
(Prime)
F300W,F450W,F606W,F814W
9481
Gardner
200
(Parallel)
F300W
9318
Casertano
(Pure Parallel)
F300W,F410M,F450W,F467M,F606W,F814W
9319
Casertano
(Pure Parallel)
F300W,F606W
Note: Other Cycle 11 GO Programs are also now using WFPC2 in parallel.
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SPACE TELESCOPE SCIENCE INSTITUTE
TIPS: 21 February 2002
WFPC2
Anton Koekemoer
WFPC2 SM3B Preparations
State of WFPC2 after HST release
• WFPC2 will be placed in PROTECT/DECON (+22 C)
• Cooldown to -88 C as soon as practical after end of 12-day BEA
WFPC2 Pre-SM3B Calibration Program
• 8943: WFPC2 Lyman-Alpha Check: Pre-SM3B Baseline (Nov. 2001)
WFPC2 SMOV Calibration Programs
• 8950: WFPC2 SM3B Cooldown, Contamination Monitors,
Photometric Monitors, Internal Calibrations, Focus Checks
• 8951: WFPC2 SM3B Lyman-Alpha Check
• 8952: WFPC2 SM3B Flat Field Calibration
• 8953: WFPC2 SM3B Relative Photometry Check
• 8954: WFPC2 SM3B Point Spread Function Verification
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SPACE TELESCOPE SCIENCE INSTITUTE
TIPS: 21 February 2002
WFPC2
Anton Koekemoer
WFPC2 Software Development
Revised WFPC2 Exposure Time Calculator (Biretta et al.)
• Additional options for photometry (either “optimal PSF weighting or simple
aperture photometry in a user-specified radius)
• More flexible background specification:
– high/average/low, or explicit user-specified value
– sky backgrounds calculated based on target position and sun angle
Dither Working Group (Koekemoer et al.)
• Cross-instrument group to coordinate testing new release of drizzle2.6 for
WFPC2, STIS, NICMOS (and also PyDrizzle, in conjunction with ACS team)
• Forum for discussing specifications for future dither software
New Darks software (Platais, Riess, Koekemoer)
• Software to facilitate creation of darks by users
5
SPACE TELESCOPE SCIENCE INSTITUTE
TIPS: 21 February 2002
WFPC2
Anton Koekemoer
WFPC2 Filter Wheel Rotation Anomaly
(Gonzaga et al., ISR in preparation)
Was discovered during routine checks of gain ratios over time:
• Measurement of average countrate in central 400x400 pixels ofVISFLAT
images (in FR533N), for gain 7 relative to gain 15
• Nominal ratio should remain constant ~ 1.97
• “Quantized” jumps were found above and below this value, to 1.90 and 2.05
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SPACE TELESCOPE SCIENCE INSTITUTE
TIPS: 21 February 2002
WFPC2
Anton Koekemoer
Visual inspection revealed spatial shifts in filter features on the images:
Example: two WF3 images in the FR533N filter, showing a shift of ~10 pixels
7
SPACE TELESCOPE SCIENCE INSTITUTE
TIPS: 21 February 2002
WFPC2
Anton Koekemoer
More quantitative measurement of shift: plot cross-sections
Example: Vertical cross-section taken through two FQCH4N VISFLAT images
(i.e. varying y-pixel location, for a constant x-pixel location):
Average of Columns 1110 to 1130 in Mosaic’d images u2qq1707t & u2qq0z07p
1500
1250
Measured Region
at approx. (1120,700)
Counts
1000
750
500
250
0
250
500
750
Rows
1000
1250
1500
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SPACE TELESCOPE SCIENCE INSTITUTE
Could the shift be caused by filter wheel displacements?
Filter Wheel Layout:
2.277 inches
(2077.8 pix)
WFPC2 Geometry:
Filter Wheel
Rotation Axis
TIPS: 21 February 2002
WFPC2
Anton Koekemoer
9
SPACE TELESCOPE SCIENCE INSTITUTE
TIPS: 21 February 2002
WFPC2
Anton Koekemoer
Use the measured x,y shifts to calculate a rotation offset angle:
Typical values for the rotational displacement are ~0.4 - 0.5 deg.
Final filter movement is sensed by means of IR LED encoder -> possibilities:
• damping pulse for final filter placement is becoming erratic
• Radiation degradation may be affecting the LED/sensor mechanism
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