16441( 2) - 12-Nov-2020 20:51:16 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16441 Version: 2 Check-in Time: 12-Nov-2020 20:51:16 STScI Edit Number: 0 Title Understanding How CTE Affects the Faintest Point Sources in WFC3/UVIS ------------------------------------------------------------------------------------ Type Cycle CAL/WFC3 28 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Jay Anderson Space Telescope Science Institute Y CoI: Benjamin Kuhn Space Telescope Science Institute N CoI: Dr. Sylvia M. Baggett Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract The calibration programs (such as CAL-16440) that attempt to pin-down the parameters of the CTE model involve a study of warm pixels. This is approprate for evaluating the pixel-based model, however stars are different from warm pixels. Their profiles involve multiple pixels, and the downstream pixels can have a significant shielding effect on the upstream pixels. Although the pixel-based models include this effect in principle, it is hard to evaluate exactly how shielding in the model compares with shielding in the real detectors. Therefore, it is useful to observe actual stars to evaluate the model. In addition, one complication of the model involves the readnoise. The pixel-based CTE correction is a necessarily deconvolution process. The readnoise was added after the CTE-blurring took place, therefore its noise will be amplified by any pixel-based reconstruction process. For faint sources, it may sometimes be preferable to forego the pixel-based reconstruction (which can amplify readnoise and diminish the significance of the sources) and analyze the _flt images directly, doing the CTE correction as part of the analysis. The observations in this program will allow users to construct photometric and astrometric corrections for the impact of CTE on faint sources on various backgrounds. Finally, this program will provide advice to users about how much post-flash to add to maximize the signal-to-noise of their sources. A higher background will preserve more signal, while also increasing the noise. This program is similar to CAL-14881, except that the target is Omega Cen instead of the bulge and we are finely sampling sky levels between 10e and 30e for UVIS, so that users can dial in the background level that optimizes the signal to noise of their program. The previous program sampled a less useful, wider variety of backgrounds. We are also observing ACS in parallel at 4 background levels. ------------------------------------------------------------------------------------ Observations Description ------------------------ This program involves two external orbits. We will place WFC3/UVIS on the center of globular cluster Omega Centauri, and ACS in parallel on a field that is about 6' away. In each orbit, we are able to collect four short and two deep full-frame WFC3/UVIS exposures per orbit, and two short and two deep 2Kx2K subarray ACS observations. 16441( 2) - 12-Nov-2020 20:51:16 - [ 2] There will be no dithering in this program, since the goal is to establish the "true" scene from the 800s deep exposures, then to downscale this true scene to the short exposures with different backgrounds in order to see how the background level affects the distribution/preservation of charge. From the archive, 40s exposures of the scene at the center of Omega Cen have a background of 26e in WFC3/UVIS. This is way too high for our purposes of exploring the background between 10e and 30e. So we will scale down these exposure times to 4s so that we can get a background of 2.6e. We can then add postflash to get it into our desired range. For ACS at a 6' removed field, the natural background should be quite small, so our postflash will define the background. For UVIS we will probe 8 background levels: 10e, 12e, 14e, 16e, 19e, 22e, 25e, and 29e. For ACS we will probe 4 backgrond levels: 10e, 20e, 30e, and 40e. 4s exposures should have ~30, 000 stars in each UVIS field in each magnitude bin at the faint end. This will provide us a very clear measurement of how stellar profiles vary with flux and background level. The deep exposures will be 800s, so we will scale them down by a factor of 200, which will provide a very robust "truth" image for evaluating the short exposures. Saturation in the deep exposures should not have a big impact. ------------------------------------------------------------------------------------ 16441( 2) - 12-Nov-2020 20:51:16 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-5139 EXT-CLUSTER, GLOBULAR RA=13H26M47.2800S, J2000 V = 5.33 CLUSTER DEC=-47D28'46.20" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2015.5 -3.1959567280703653E-4 -0.006729999904564465 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 16441( 2) - 12-Nov-2020 20:51:16 - [ 4] Visit: 02 (EXTERNAL-CTE-CHECK) Visit Requirements: BETWEEN 11-NOV-2020 AND 15-JAN-2021 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-5139 WFC3/UVI ACCUM UVIS F606W FLASH=6, BLADE=A 1 4 S (4 S) POS TARG null, 0; PAR S 4-5 WITH 1-3 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-5139 WFC3/UVI ACCUM UVIS F606W FLASH=8, BLADE=A 1 4 S (4 S) SAME POS AS 1 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-5139 WFC3/UVI ACCUM UVIS F606W 1 800 S (800 SAME POS AS 1 S S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY ACS/WFC ACCUM WFC1B-2K F606W FLASH=10 1 4 S (4 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 ANY ACS/WFC ACCUM WFC1B-2K F606W 1 800 S (800 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC-5139 WFC3/UVI ACCUM UVIS F606W FLASH=10, BLADE=A 1 4 S (4 S) PAR 9-10 WITH 6-8 S ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC-5139 WFC3/UVI ACCUM UVIS F606W FLASH=12, BLADE=A 1 4 S (4 S) S ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC-5139 WFC3/UVI ACCUM UVIS F606W 1 800 S (800 S S) ------------------------------------------------------------------------------------------------------------------------------------ 9 ANY ACS/WFC ACCUM WFC1B-2K F606W FLASH=20 1 4 S (4 S) ------------------------------------------------------------------------------------------------------------------------------------ 10 ANY ACS/WFC ACCUM WFC1B-2K F606W 1 800 S (800 S) ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC-5139 WFC3/UVI ACCUM UVIS F606W FLASH=15, BLADE=A 1 4 S (4 S) POS TARG null, 0; PAR S 14-15 WITH 11-13 ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC-5139 WFC3/UVI ACCUM UVIS F606W FLASH=18, BLADE=A 1 4 S (4 S) S ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC-5139 WFC3/UVI ACCUM UVIS F606W 1 800 S (800 S S) ------------------------------------------------------------------------------------------------------------------------------------ 14 ANY ACS/WFC ACCUM WFC1B-2K F606W FLASH=30 1 4 S (4 S) ------------------------------------------------------------------------------------------------------------------------------------ 15 ANY ACS/WFC ACCUM WFC1B-2K F606W 1 800 S (800 S) ------------------------------------------------------------------------------------------------------------------------------------ 16441( 2) - 12-Nov-2020 20:51:16 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 16 NGC-5139 WFC3/UVI ACCUM UVIS F606W FLASH=21, BLADE=A 1 4 S (4 S) PAR 19-20 WITH 16-18 S ------------------------------------------------------------------------------------------------------------------------------------ 17 NGC-5139 WFC3/UVI ACCUM UVIS F606W FLASH=25, BLADE=A 1 4 S (4 S) S ------------------------------------------------------------------------------------------------------------------------------------ 18 NGC-5139 WFC3/UVI ACCUM UVIS F606W 1 800 S (800 S S) ------------------------------------------------------------------------------------------------------------------------------------ 19 ANY ACS/WFC ACCUM WFC1B-2K F606W FLASH=40 1 4 S (4 S) ------------------------------------------------------------------------------------------------------------------------------------ 20 ANY ACS/WFC ACCUM WFC1B-2K F606W 1 800 S (800 S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-5139 1 WFC3/UVI ACCUM UVIS F606W none none none none 1 N/A S NGC-5139 2 WFC3/UVI ACCUM UVIS F606W none none none none 1 N/A S NGC-5139 3 WFC3/UVI ACCUM UVIS F606W none none none none 1 N/A S ANY 4 ACS/WFC ACCUM WFC1B-2K F606W none none none none 1 N/A ANY 5 ACS/WFC ACCUM WFC1B-2K F606W none none none none 1 N/A NGC-5139 6 WFC3/UVI ACCUM UVIS F606W none none none none 1 N/A S NGC-5139 7 WFC3/UVI ACCUM UVIS F606W none none none none 1 N/A S NGC-5139 8 WFC3/UVI ACCUM UVIS F606W none none none none 1 N/A S ANY 9 ACS/WFC ACCUM WFC1B-2K F606W none none none none 1 N/A ANY 10 ACS/WFC ACCUM WFC1B-2K F606W none none none none 1 N/A NGC-5139 11 WFC3/UVI ACCUM UVIS F606W none none none none 2 N/A S NGC-5139 12 WFC3/UVI ACCUM UVIS F606W none none none none 2 N/A S NGC-5139 13 WFC3/UVI ACCUM UVIS F606W none none none none 2 N/A S ANY 14 ACS/WFC ACCUM WFC1B-2K F606W none none none none 2 N/A ANY 15 ACS/WFC ACCUM WFC1B-2K F606W none none none none 2 N/A NGC-5139 16 WFC3/UVI ACCUM UVIS F606W none none none none 2 N/A S 16441( 2) - 12-Nov-2020 20:51:16 - [ 6] 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-5139 17 WFC3/UVI ACCUM UVIS F606W none none none none 2 N/A S NGC-5139 18 WFC3/UVI ACCUM UVIS F606W none none none none 2 N/A S ANY 19 ACS/WFC ACCUM WFC1B-2K F606W none none none none 2 N/A ANY 20 ACS/WFC ACCUM WFC1B-2K F606W none none none none 2 N/A 16441( 2) - 12-Nov-2020 20:51:16 - [ 7] Summary Form for Proposal 16441 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS, WFC1B-2K ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BLADE=A, FLASH=10, FLASH=12, FLASH=15, FLASH=18, FLASH=20, FLASH=21, FLASH=25, FLASH=30, FLASH=40, FLASH=6, FLASH=8 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 11-NOV-2020 AND 15-JAN-2021, PAR 14-15 WITH 11-13, PAR 19-20 WITH 16-18, PAR 4-5 WITH 1-3, PAR 9-10 WITH 6-8, POS TARG null, 0, SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ANY, NGC-5139 ------------------------------------------------------------------------------------------------------------------------------------