13066( 2) - 17-Jul-2012 15:40:25 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13066 Version: 2 Check-in Time: 17-Jul-2012 15:40:25 STScI Edit Number: 0 Title ACS Postflash Characterization ------------------------------------------------------------------------------------ Type Cycle CAL/ACS 19 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Linda J. Smith Space Telescope Science Institute - ESA Y CoI: Dr. Marco Chiaberge Space Telescope Science Institute - ESA N CoI: Dr. Jay Anderson Space Telescope Science Institute N CoI: Ms. Sara Ogaz Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract This program will evaluate the in-flight performance of the ACS/WFC post-flash lamp. A series of observations of Omega Cen will be taken using short and long exposures. The short exposures will be post-flashed using pre-determined exposure times to produce backgrounds from 0 to 125 e-. The data will be used to (1) make an empirical study of the effectiveness in preserving counts for faint stars on various post-flash backgrounds; (2) validate that our current mechanisms for formula-based and pixel-based corrections provide good fixes for whatever CTE remains; and (3) probe a fine enough range of backgrounds that users will be able to pick the level that optimizes their science, which will be a straightforward compromise between the noise added and the signal preserved. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will obtain external data to determine the optimum background for CTE mitigation. We propose to observe the same target as UVIS i.e. the centre of Omega Cen. This has two advantages: we can do a direct comparison with the UVIS findings; and the WFC and UVIS observations can be used later to check the accuracy of the geometric distortion solutions for the two cameras. We will use the F435W filter and take pairs of short and long exposures. By taking all the exposures in short-long pairs, we do not need to worry about aperture corrections as we can measure all stars with the same aperture in short-long, so the only difference will be the losses in the shorts as a function of background level and source level (which is what we're trying to probe). In each orbit, we will obtain 3 short-long pairs and thus in 3 orbits, we will obtain data for 9 different post-flash levels. This number of different levels is necessary because we do not anticipate that ACS (unlike UVIS) will have a single level (or sweet spot) where the transfer quality increases markedly. We will use these 9 different levels to produce a background/loss curve to give to users so that they can decide the post-flash level that is most appropriate for their observations. Background levels used = 0, 10, 20, 30, 45, 60, 75, 100 and 125 e- 13066( 2) - 17-Jul-2012 15:40:25 - [ 2] corresponding to exposure times of 0, 1.2, 2.4, 3.6, 5.4, 7.2, 9.1, 12.1 and 15.1 s for FLASHCURR=LOW. Each exposure is dithered in x only to separate out stars and hot pixels so that both can be used in the analysis. The dither pattern is 0, +10, +20, +15, +5, -5, -15, -20 and -10 x pixels Each orbit is arranged so that the same shutter blade is used for each post-flash to minimize the known variation in the illumination between blades A and B. It not known a priori which blade will be used. There is one F606W exposure at the end of orbit 2. To keep the same blade for the post flash shorts, the order is changed to long-short-long-short etc. in orbit 3. Visit 02 is on hold. It differs from visit 01 in that the sequence is short-long short-long in orbit 3. This visit should be executed instead of visit 01 if the flight software update to initialise the ACS shutter has been carried out. This should ensure that the same shutter blade is used for every post-flash. Real Time Justification ----------------------- Calibration Justification ------------------------- The data will be used to quantify the trade-off between the level of CTE mitigation achieved and the level of noise introduced into the data as a function of the post-flash exposure time/background level. Additional Comments ------------------- ------------------------------------------------------------------------------------ 13066( 2) - 17-Jul-2012 15:40:25 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 OMEGACEN STELLAR CLUSTER, RA=13H26M47.2400S +/- 0.1", J2000 V = 16.8 GLOBULAR CLUSTER DEC=-47D29'17.95" +/- 0.1" Reference Frame: ICRS Comments: Pointing based on SMOV proposal 11452. ------------------------------------------------------------------------------------------------------------------------------------ 13066( 2) - 17-Jul-2012 15:40:25 - [ 4] Visit: 01 Visit Requirements: BEFORE 31-AUG-2012 On Hold Comments: Additional Comments: This visit should be executed if the FSW update is not ready to initialise the shutter. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 6 S ------------------------------------------------------------------------------------------------------------------------------------ 2 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S ------------------------------------------------------------------------------------------------------------------------------------ 3 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG +0.494, +0.040 FLASHEXP=1.2 ------------------------------------------------------------------------------------------------------------------------------------ 4 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG +0.494, +0.040 ------------------------------------------------------------------------------------------------------------------------------------ 5 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG 0.988, 0.08 FLASHEXP=2.4 ------------------------------------------------------------------------------------------------------------------------------------ 6 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG 0.988, 0.08 ------------------------------------------------------------------------------------------------------------------------------------ 7 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG +0.741, +0.060 FLASHEXP=3.6 ------------------------------------------------------------------------------------------------------------------------------------ 8 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG +0.741, +0.060 ------------------------------------------------------------------------------------------------------------------------------------ 9 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG +0.247, +0.020 FLASHEXP=5.4 ------------------------------------------------------------------------------------------------------------------------------------ 10 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG +0.247, +0.020 ------------------------------------------------------------------------------------------------------------------------------------ 11 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG -0.247, -0.020 FLASHEXP=7.2 ------------------------------------------------------------------------------------------------------------------------------------ 12 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG -0.247, -0.020 ------------------------------------------------------------------------------------------------------------------------------------ 13 OMEGACEN ACS/WFC ACCUM WFC F606W CR-SPLIT=NO 1 339 S POS TARG -0.247, -0.020 ------------------------------------------------------------------------------------------------------------------------------------ 14 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG -0.741, -0.060 ------------------------------------------------------------------------------------------------------------------------------------ 15 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG -0.741, -0.060 FLASHEXP=9.1 ------------------------------------------------------------------------------------------------------------------------------------ 16 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG -0.988, -0.080 ------------------------------------------------------------------------------------------------------------------------------------ 17 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG -0.988, -0.080 FLASHEXP=12.1 ------------------------------------------------------------------------------------------------------------------------------------ 18 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG -0.494, -0.040 13066( 2) - 17-Jul-2012 15:40:25 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------------------------ 19 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG -0.494, -0.040 FLASHEXP=15.1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ OMEGACEN 1 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 2 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 3 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 4 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 5 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 6 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 7 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 8 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 9 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 10 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 11 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 12 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 13 ACS/WFC ACCUM WFC F606W none none none none 2 N/A OMEGACEN 14 ACS/WFC ACCUM WFC F435W none none none none 3 N/A OMEGACEN 15 ACS/WFC ACCUM WFC F435W none none none none 3 N/A OMEGACEN 16 ACS/WFC ACCUM WFC F435W none none none none 3 N/A OMEGACEN 17 ACS/WFC ACCUM WFC F435W none none none none 3 N/A OMEGACEN 18 ACS/WFC ACCUM WFC F435W none none none none 3 N/A OMEGACEN 19 ACS/WFC ACCUM WFC F435W none none none none 3 N/A 13066( 2) - 17-Jul-2012 15:40:25 - [ 6] Visit: 02 Visit Requirements: BEFORE 31-AUG-2012; ON HOLD On Hold Comments: This visit should only be executed instead of visit 01 if the FSW update to initialise the ACS shutter mechanism is in place. Additional Comments: This visit should only be executed instead of visit 01 if the FSW update to initialise the ACS shutter mechanism is in place. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 6 S ------------------------------------------------------------------------------------------------------------------------------------ 2 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S ------------------------------------------------------------------------------------------------------------------------------------ 3 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG +0.494, +0.040 FLASHEXP=1.2 ------------------------------------------------------------------------------------------------------------------------------------ 4 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG +0.494, +0.040 ------------------------------------------------------------------------------------------------------------------------------------ 5 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG 0.988, 0.08 FLASHEXP=2.4 ------------------------------------------------------------------------------------------------------------------------------------ 6 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG 0.988, 0.08 ------------------------------------------------------------------------------------------------------------------------------------ 7 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG +0.741, +0.060 FLASHEXP=3.6 ------------------------------------------------------------------------------------------------------------------------------------ 8 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG +0.741, +0.060 ------------------------------------------------------------------------------------------------------------------------------------ 9 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG +0.247, +0.020 FLASHEXP=5.4 ------------------------------------------------------------------------------------------------------------------------------------ 10 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG +0.247, +0.020 ------------------------------------------------------------------------------------------------------------------------------------ 11 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG -0.247, -0.020 FLASHEXP=7.2 ------------------------------------------------------------------------------------------------------------------------------------ 12 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG -0.247, -0.020 ------------------------------------------------------------------------------------------------------------------------------------ 13 OMEGACEN ACS/WFC ACCUM WFC F606W CR-SPLIT=NO 1 339 S POS TARG -0.247, -0.020 ------------------------------------------------------------------------------------------------------------------------------------ 14 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG -0.741, -0.060 FLASHEXP=9.1 ------------------------------------------------------------------------------------------------------------------------------------ 15 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG -0.741, -0.060 ------------------------------------------------------------------------------------------------------------------------------------ 16 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG -0.988, -0.080 FLASHEXP=12.1 ------------------------------------------------------------------------------------------------------------------------------------ 17 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG -0.988, -0.080 13066( 2) - 17-Jul-2012 15:40:25 - [ 7] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------------------------ 18 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO, FLASHCUR=LOW, 1 6 S POS TARG -0.494, -0.040 FLASHEXP=15.1 ------------------------------------------------------------------------------------------------------------------------------------ 19 OMEGACEN ACS/WFC ACCUM WFC F435W CR-SPLIT=NO 1 339 S POS TARG -0.494, -0.040 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ OMEGACEN 1 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 2 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 3 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 4 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 5 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 6 ACS/WFC ACCUM WFC F435W none none none none 1 N/A OMEGACEN 7 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 8 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 9 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 10 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 11 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 12 ACS/WFC ACCUM WFC F435W none none none none 2 N/A OMEGACEN 13 ACS/WFC ACCUM WFC F606W none none none none 2 N/A OMEGACEN 14 ACS/WFC ACCUM WFC F435W none none none none 3 N/A OMEGACEN 15 ACS/WFC ACCUM WFC F435W none none none none 3 N/A OMEGACEN 16 ACS/WFC ACCUM WFC F435W none none none none 3 N/A OMEGACEN 17 ACS/WFC ACCUM WFC F435W none none none none 3 N/A OMEGACEN 18 ACS/WFC ACCUM WFC F435W none none none none 3 N/A OMEGACEN 19 ACS/WFC ACCUM WFC F435W none none none none 3 N/A 13066( 2) - 17-Jul-2012 15:40:25 - [ 8] Summary Form for Proposal 13066 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO, FLASHCUR=LOW, FLASHEXP=1.2, FLASHEXP=12.1, FLASHEXP=15.1, FLASHEXP=2.4, FLASHEXP=3.6, FLASHEXP=5.4, FLASHEXP=7.2, FLASHEXP=9.1 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BEFORE 31-AUG-2012, ON HOLD , POS TARG +0.247, +0.020, POS TARG +0.494, +0.040, POS TARG +0.741, +0.060, POS TARG -0.247, -0.020, POS TARG -0.494, -0.040, POS TARG -0.741, -0.060, POS TARG -0.988, -0.080, POS TARG 0.988, 0.08 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F435W, F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names OMEGACEN ------------------------------------------------------------------------------------------------------------------------------------