0 This the first (complete) submission of this Cycle-28 WFC3 non-monitor program. This program requests 2 visits (each 1-orbit) to be executed between Dec 20 2021 - Jan 20 2022 & Mar 20 2022 - Apr 20 2022, respectively. -509110725 ----- Attempting Submission 1 (Wed Jun 30 03:20:26 GMT 2021) ----- WFC3/IR Time-Dependent Sensitivity We aim to measure the time dependent sensitivity loss for WFC3/IR using spatial scans of the open cluster M35. We use spatial scanning as the SNR achieved from scanning is higher than conventional staring observations. The spatial scans build on the F140W observations performed in HST program 14020 and the F140W and F098M observations performed in HST program 16031. The observations are performed over two identical visits ~3 months apart and the observation structure in each visit is also identical with that executed in program 16031. The proposed data will extend the existing baseine by ~1 year and the short interval between the visits will provide additional sampling for the short-term repeatability analysis. The two spatial scan visits are identical, but executed approximately ~3 months apart. Observations in each visit is executed with the following strategy: The first observation is a simple direct image in F140W. The next 4 exposures are hortizontal spatial scans (length ~13.2") in F140W with sequential dithers of 1 arcsecond, perpendicular to the scan direction (the -Y direction), between exposures, as to match the experiment performed in 14020. The following 10 exposures are performed in the same way, however with dithers of 1.4 arcseconds to further mitigate persistence. There are then 3 exposures taken with F098M, with the same 1.4" dithers in between each exposure. This puts one of the target stars at the bottom of the detector, allowing, no further dithering in the previous direction. Then, a large 17 arcsecond dither is performed in the -X direction (to avoid scanning on the same pixels where the star already landed), and 3 more F098M observations are taken, with subsequent dithers of 1.4" in the +Y direction. We then switch back to F140W and take 5 more observations, with dithers of 3" between exposures, as to ensure persistence is mitigated. Lastly, we take a dark exposure with the same sample sequence (but using 11 reads) as to characterize persistence. 0 false false RESTRICTED STELLAR CLUSTER OPEN CLUSTER This object was generated by the targetselector and retrieved from the SIMBAD database. An advantage of an open cluster is that it is not too dense like a globular, and an open cluster will contain a lot of (photometrically stable) main sequence stars. J2000 The scheduling data was generated by CASM 29.2. CASM was run in Phase II mode. /Users/dsom/workarea/WFC3_projects/Cy28_Cal/special_cal/M34_IR_spatialscan/OP-cache/16439-v01.xml (Tic-Visit :proposal-id 16439 :visit-id "01" :proposal-version -1 :trans-version "20200619" :date "16-Jun-2021 11:32:49.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 408976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16439 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16439 :visit-id "01" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2730 :al-overhead-at-end 0 :internal-dur-at-end 528 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3157 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 29.2. CASM was run in Phase II mode. /Users/dsom/workarea/WFC3_projects/Cy28_Cal/special_cal/M34_IR_spatialscan/OP-cache/16439-v02.xml (Tic-Visit :proposal-id 16439 :visit-id "02" :proposal-version -1 :trans-version "20200619" :date "16-Jun-2021 11:32:55.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 408976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16439 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16439 :visit-id "02" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2730 :al-overhead-at-end 0 :internal-dur-at-end 528 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3157 :pcs-gap 0 ) true 1 0