17271( 2) - 22-Dec-2022 19:53:48 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17271 Version: 2 Check-in Time: 22-Dec-2022 19:53:48 STScI Edit Number: 0 Title WFC3 UVIS Deep PSFs ------------------------------------------------------------------------------------ Type Cycle CAL/WFC3 30 ------------------------------------------------------------------------------------ Investigators Contact? PI: Varun Bajaj Space Telescope Science Institute Y CoI: Dr. Annalisa Calamida Space Telescope Science Institute N CoI: Ms. Jennifer Mack Space Telescope Science Institute N CoI: Mariarosa Marinelli Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract The UVIS PSF will be sampled in 5 different filters to measure the fraction of light in the PSF at large radii (>150 pixels), by exposing a bright star well past the point of saturation in the core. By observing GRW+70 5824, a frequently observed spectrophotometric standard star, we circumvent the issues high level of saturation in the core of the PSF imparted by thelong exposure times, as the flux of this source is well characterized by other calibration programs. Thus, the signal in the wings of the PSF is allowed to integrate significantly, and can be compared to the flux in the core of the PSF from other observations. This measurement of the PSF wings in these filters allows for better computation of aperture corrections for extended objects, as well as better PSF modeling. Currently, the encircled energy models for the UVIS filters terminate at 150 pixel (6 arcseconds) and are assumed to contain 100% of the light. However, measurementsof data taken in HST 11919 show that 1-2% of the flux of the source lies within 150-700 pixels in F275W/F625W. These errors in the encircled energy curves thus overpredict the amount of light inside 150 pixels, and lead to errors in the absolute measurements of flux from spatial scans. The filters chosen in this experiment are some of the most used wide band UVIS filters, and cover the majority of the wavelength range observable by the UVIS channel, so other filters encircled energy models may be adjusted via interpolating the results from these filters. ------------------------------------------------------------------------------------ Observations Description ------------------------ The bright, isolated white dwarf star GRW+70 5824 will be observed in F225W, F336W, F475W, F555W, and F814W using pairs of long exposures, which will saturate the core of the PSF, but allow siginficant signal to be accrued in the wings of the PSF. In the first orbit, we take 6 exposures (F814W is observed twice to compensate for the source's lower brightness in this band). At the end of the first orbit, a small dither of 10.5 pixels in X and Y is applied (to mitigate bad pixel effects) and the exposures in orbit 1 are repeated. We select the same apeture (UVIS CENTER) and POS TARG used in 11919 that placed the source in amp C, as this is the most observed/stable position on the detector. This helps reduce effects from the flatfield and other calibrations having spatial errors, when compared to the typical standard star monitoring 17271( 2) - 22-Dec-2022 19:53:48 - [ 2] observations. The exposure times for each filter are selected to give a similar total number of electrons (and thus SNR) deposited on the detector across all 5 filters, while allowing buffer dumps during the exposure in the middle of the orbits, maximizing orbital efficiency. We use computed flash levels to bring the per pixel flash levels to approximately 20 electrons to mitigate CTE effects. ------------------------------------------------------------------------------------ 17271( 2) - 22-Dec-2022 19:53:48 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 3 GRW+70 CALIBRATION, RA=13H38M49.2465S, J2000 V = 12.6 PHOTOMETRIC DEC=+70D17'7.26" Reference Frame: Other: SIMBAD Extended: NO 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 -0.07946163100704791 -0.024556000062148087 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 17271( 2) - 22-Dec-2022 19:53:48 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.582 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17271( 2) - 22-Dec-2022 19:53:48 - [ 5] Visit: 01 Visit Requirements: AFTER 28-FEB-2023:00:00:00 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 GRW+70 WFC3/UVI ACCUM UVIS-CENT F475W FLASH=14 1 250 S (500 POS TARG -50.7, -54.9; S ER S) PATTERN 1 1-6 ------------------------------------------------------------------------------------------------------------------------------------ 2 GRW+70 WFC3/UVI ACCUM UVIS-CENT F814W FLASH=14 1 375 S (750 POS TARG -50.7, -54.9 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 3 GRW+70 WFC3/UVI ACCUM UVIS-CENT F814W FLASH=14 1 375 S (750 POS TARG -50.7, -54.9 S ER S) ------------------------------------------------------------------------------------------------------------------------------------ 4 GRW+70 WFC3/UVI ACCUM UVIS-CENT F225W FLASH=20 1 560 S POS TARG -50.7, -54.9 S ER (1120 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 GRW+70 WFC3/UVI ACCUM UVIS-CENT F336W FLASH=20 1 500 S POS TARG -50.7, -54.9 S ER (1000 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 GRW+70 WFC3/UVI ACCUM UVIS-CENT F555W FLASH=13 1 250 S (500 POS TARG -50.7, -54.9 S ER 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 | ------------------------------------------------------------------------------------------------------------------------------------ GRW+70 1 WFC3/UVI ACCUM UVIS-CEN F475W 1 none none none 1 N/A S TER GRW+70 1 WFC3/UVI ACCUM UVIS-CEN F475W 2 none none none 2 N/A S TER GRW+70 2 WFC3/UVI ACCUM UVIS-CEN F814W 1 none none none 1 N/A S TER GRW+70 2 WFC3/UVI ACCUM UVIS-CEN F814W 2 none none none 2 N/A S TER GRW+70 3 WFC3/UVI ACCUM UVIS-CEN F814W 1 none none none 1 N/A S TER GRW+70 3 WFC3/UVI ACCUM UVIS-CEN F814W 2 none none none 2 N/A S TER GRW+70 4 WFC3/UVI ACCUM UVIS-CEN F225W 1 none none none 1 N/A S TER GRW+70 4 WFC3/UVI ACCUM UVIS-CEN F225W 2 none none none 2 N/A S TER GRW+70 5 WFC3/UVI ACCUM UVIS-CEN F336W 1 none none none 1 N/A S TER 17271( 2) - 22-Dec-2022 19:53:48 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GRW+70 5 WFC3/UVI ACCUM UVIS-CEN F336W 2 none none none 2 N/A S TER GRW+70 6 WFC3/UVI ACCUM UVIS-CEN F555W 1 none none none 1 N/A S TER GRW+70 6 WFC3/UVI ACCUM UVIS-CEN F555W 2 none none none 2 N/A S TER 17271( 2) - 22-Dec-2022 19:53:48 - [ 7] Summary Form for Proposal 17271 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-CENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=13, FLASH=14, FLASH=20 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 28-FEB-2023:00:00:00, PATTERN 1 1-6, POS TARG -50.7, -54.9 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F225W, F336W, F475W, F555W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GRW+70 ------------------------------------------------------------------------------------------------------------------------------------