12395( 8) - 10-Feb-2011 21:20:13 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12395 Version: 8 Check-in Time: 10-Feb-2011 21:20:13 STScI Edit Number: 0 Title Bias Shift Calibration ------------------------------------------------------------------------------------ Type Cycle CAL/ACS 18 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. David A. Golimowski Space Telescope Science Institute CoI: Dr. Anatoly Suchkov The Johns Hopkins University N ------------------------------------------------------------------------------------ Abstract This program provides images of an extended source with uniform brightness and sharp boundaries (Saturn's rings) that are needed for accurate calibration of the parametric solution for the signal-dependent offset and decay of the bias levels for each WFC CCD quadrant. This phenomenon, colloquially known as "bias shift" is a feature of the dual-slope integrator implemented in the WFC CEB-R after SM4. ------------------------------------------------------------------------------------ Observations Description ------------------------ Narrow-band images of Saturn will be obtained in all four quadrants of the WFC CCDs in order to characterize the bias shift phenomenon in each quadrant. Saturn will be acquired at positions near and far from the read out node in each quadrant and at an orient that aligns the projected major axis of the rings with the CCD columns. This orient provides sharp-edged illumination from the rings along a maximal number of CCD rows and also aligns the sharp boundaries of the planet near the orbital poles with the CCD rows. Two narrowband (F502N) exposures of Saturn will be taken at two column positions in each quadrant, for a total of eight WFC exposures. Because Saturn is bright and the exposures are short, only 4 full-frame images can be recorded per orbit. (Full frame images are needed to determine whether there is any cross-amplifier correlation of the bias shift effect.) The data will have S/N = 250 per pixel, which is sufficient to accurately measure the 0.01-0.02% bias shift effect in each quadrant. Real Time Justification ----------------------- Calibration Justification ------------------------- All GO/GTO programs that feature high contrast targets (e.g., circumstellar emission, nebulae with embedded or superposed stars) will benefit from the removal of the elevated and smeared bias signal imposed during signal processing of each image pixel. Proper characterization of the bias shift will also enable more accurate measurement and correction of the horizontal component of the CCDs' charge transfer efficiency. Deconvolving the effects of bias shift and horizontal CTE will improve the quality of all calibrated images 12395( 8) - 10-Feb-2011 21:20:13 - [ 2] when these separate corrections are implemented into CALACS in Cycle 19. The data will constrain the parameters of the analytic bias-shift correction formula derived by Markus Loose. This formula will be the basis of a new CALACS module to be implemented in the calibration pipeline along with bias stripe and pixel-based CTE correction modules. Additional Comments ------------------- ------------------------------------------------------------------------------------ 12395( 8) - 10-Feb-2011 21:20:13 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET OFFSET SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 0.8 +/- 0.1 Visual magnitude on 01-JAN-2011: V = 0.8 mag; surface brightness = 6.6 mag/arcsec^2 Visual magnitude on 31-MAR-2011: V = 0.4 mag; surface Ephemeris Center: EARTH brightness = 6.4 mag/arcsec^2 ------------------------------------------------------------------------------------------------------------------------------------ 12395( 8) - 10-Feb-2011 21:20:13 - [ 4] Visit: 01 Visit Requirements: ORIENT 86D TO 88 D; ORIENT 266D TO 268 D On Hold Comments: Additional Comments: Orient range restricted to align Saturn's polar axis with the CCD rows. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SATURN ACS/WFC ACCUM WFC1-FIX F502N 1 10 S POS TARG -87.24, 20.30; GS ACQ SCENARIO SINGLE ------------------------------------------------------------------------------------------------------------------------------------ 2 SATURN ACS/WFC ACCUM WFC1-FIX F502N 1 10 S POS TARG -13.93, 26.24 ------------------------------------------------------------------------------------------------------------------------------------ 3 SATURN ACS/WFC ACCUM WFC1-FIX F502N 1 10 S POS TARG 13.93, 28.50; GS ACQ SCENARIO SINGLE ------------------------------------------------------------------------------------------------------------------------------------ 4 SATURN ACS/WFC ACCUM WFC1-FIX F502N 1 10 S POS TARG 87.24, 34.43 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SATURN 1 ACS/WFC ACCUM WFC1-FIX F502N none none none none 1 N/A SATURN 2 ACS/WFC ACCUM WFC1-FIX F502N none none none none 1 N/A SATURN 3 ACS/WFC ACCUM WFC1-FIX F502N none none none none 1 N/A SATURN 4 ACS/WFC ACCUM WFC1-FIX F502N none none none none 1 N/A 12395( 8) - 10-Feb-2011 21:20:13 - [ 5] Visit: 02 Visit Requirements: GROUP 02, 01 WITHIN 1D On Hold Comments: Additional Comments: Orient range restricted to align Saturn's polar axis with the CCD rows. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SATURN ACS/WFC ACCUM WFC2-FIX F502N 1 10 S POS TARG -87.24, -34.43; GS ACQ SCENARIO SINGLE ------------------------------------------------------------------------------------------------------------------------------------ 2 SATURN ACS/WFC ACCUM WFC2-FIX F502N 1 10 S POS TARG -13.93, -28.50 ------------------------------------------------------------------------------------------------------------------------------------ 3 SATURN ACS/WFC ACCUM WFC2-FIX F502N 1 10 S POS TARG 13.93, -26.24; GS ACQ SCENARIO SINGLE ------------------------------------------------------------------------------------------------------------------------------------ 4 SATURN ACS/WFC ACCUM WFC2-FIX F502N 1 10 S POS TARG 87.24, -20.30 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SATURN 1 ACS/WFC ACCUM WFC2-FIX F502N none none none none 1 N/A SATURN 2 ACS/WFC ACCUM WFC2-FIX F502N none none none none 1 N/A SATURN 3 ACS/WFC ACCUM WFC2-FIX F502N none none none none 1 N/A SATURN 4 ACS/WFC ACCUM WFC2-FIX F502N none none none none 1 N/A 12395( 8) - 10-Feb-2011 21:20:13 - [ 6] Summary Form for Proposal 12395 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC1-FIX, WFC2-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GROUP 02, 01 WITHIN 1D, GS ACQ SCENARIO SINGLE, ORIENT 266D TO 268 D, ORIENT 86D TO 88 D, POS TARG -13.93, -28.50, POS TARG -13.93, 26.24, POS TARG -87.24, -34.43, POS TARG -87.24, 20.30, POS TARG 13.93, -26.24, POS TARG 13.93, 28.50, POS TARG 87.24, -20.30, POS TARG 87.24, 34.43 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F502N ------------------------------------------------------------------------------------------------------------------------------------ Target Names SATURN ------------------------------------------------------------------------------------------------------------------------------------