9662( 2) - 06/27/02 13:48 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9662 Version: 2 Check-in Date: 18-Jun-2002 08:19:49 1.Proposal Title: HRC+WFC Shutter Stability Test ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle CAL/ACS 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Ronald Gilliland Space Telescope Science Institute CoI: George Hartig Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract Some calibration observations and a small subset of GO/GTO science programs utilize exposure times down to the shortest allowed (0.1s HRC, 0.5s WFC). Shutter management varies for the shortest exposures, e.g. at 0.5s for WFC it is a continuous motion, 0.6s is not allowed, and 0.7s begins the standard mode of operation. Similar differences exist for the shortest HRC options. Ground-based testing did not establish adequate knowledge of relative exposure times, nor determine accurately the stability (repeatability) of exposure times. This program will dedicate two orbits (one each HRC and WFC) to obtaining repeated exposures at a range of short (0.1s to 5.0s HRC), (0.5s to 25s WFC) exposure times, with several repeats in a few cases in order to establish relative exposure times and stability. ------------------------------------------------------------------------------------ 9662( 2) - 06/27/02 13:48 - [ 2] Observations Description ------------------------ The core of 47 Tuc and the CLEAR filter have been chosen for the observations. In the minimum exposure time of 0.1s for the HRC stars will provide about 3.0e6 detected photons (for a formal Poisson limit of 0.0006 per exp, or an order of magnitude better than minimum required to establish relative 0.5% accuracy). At the HRC exposure time will include: 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 2.0, 5.0 and with the WFC: 0.5, 0.7, 0.8, 1.0, 2.0, 10.0, 25.0 With as many repeats spread over the shorter exposure times as can be obtained in one orbit of observations, to maximize efficiency we will select a CVZ target for this. In principle this would also be a good opportunity to test PSFs for the special case of using no filter with WFC and HRC, we will request this via special commanding. In the case of HRC where the PSF is expected to deviate only slightly from standard, this has clear science applications, for WFC the slightly blurred image will allow higher S/N per exposure to be reached. The GAIN to be used for WFC is obvious -- gain = 2 allows sampling of the full well depth, thus allowing use of saturated stars in longer exposures if desired, while still well-sampling the readout noise. For the HRC gain = 4 would be required to sample the full well, but this would no longer sample the readout noise and would complicate an accurate determination of the sky background. Gain = 2 samples read noise, but doesn't allow saturating stars to be used to establish relative exposure times. At the longest HRC exposure time of 5.0 seconds saturation at gain = 2 will occur for V < 13.2. Within the HRC FOV there will be about 15 stars this bright, and they contribute about 21% of the total flux available. 70% of the total flux is contained in ~1600 stars with 13.2 < V < 18.0. With an assumed aperture size of 177 px for V < 16 and 97 px otherwise a total of some 150, 000 pixels (some overlaps exist). To reach 1% accuracy on photometry therefore requires knowledge of the background level to about 0.1e-. This constraint argues for going with gain = 2 and sacrificing use of the 20% of flux available in stars that saturate at the longest exposures. Taking into account the flux from unsaturated stars and noise on background it should be possible to reach <0.2% relative exposure time at 0.1s. For control purposes the 1.0s exposure times will be interleaved with others for both the HRC and WFC. An even number of exposures will be taken at each level to provide both parities of shutter operation. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- The CVZ is used to improve scheduling efficiency. If necessary the same number of exposures obtained in orbits outside the CVZ would suffice. ------------------------------------------------------------------------------------ 9662( 2) - 06/27/02 13:48 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC104 STELLAR CLUSTER, RA=00H 24M 06.5156S +/- 1", DEC= J2000 V = 17.5+/-0.1 GLOBULAR CLUSTER -72D 5' 00.64" +/- 1" Coordinate Source: GUIDE_STAR_CATALOG Comments: Magnitude of main-sequence turn-off stars 9662( 2) - 06/27/02 13:48 - [ 4] Visit: 01 Visit Priority: Visit Requirements: CVZ BETWEEN 15-JUL-2002 AND 31-OCT-2002 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 6 0.1 S C Comments: Expect flux of 2e6 e- per exposure over 1500 non-saturated stars. ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 2 1.0 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 4 0.3 S C ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 2 1.0 S C ------------------------------------------------------------------------------------------------------------------------------------ 50 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 4 0.2 S C ------------------------------------------------------------------------------------------------------------------------------------ 60 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 2 1.0 S C ------------------------------------------------------------------------------------------------------------------------------------ 70 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 4 0.4 S C ------------------------------------------------------------------------------------------------------------------------------------ 80 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 2 1.0 S C ------------------------------------------------------------------------------------------------------------------------------------ 90 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 4 0.5 S C ------------------------------------------------------------------------------------------------------------------------------------ 100 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 2 1.0 S C ------------------------------------------------------------------------------------------------------------------------------------ 110 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 4 2.0 S C ------------------------------------------------------------------------------------------------------------------------------------ 120 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 2 1.0 S C ------------------------------------------------------------------------------------------------------------------------------------ 130 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 4 5.0 S C ------------------------------------------------------------------------------------------------------------------------------------ 140 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 2 1.0 S C ------------------------------------------------------------------------------------------------------------------------------------ 9662( 2) - 06/27/02 13:48 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 150 NGC104 ACS/HR ACCUM HRC CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 2 0.1 S C ------------------------------------------------------------------------------------------------------------------------------------ 160 NGC104 ACS/HR ACCUM HRC F606W CR-SPLIT=NO,PAREXP=NONE,GAIN=2 2 1.0 S C Comments: F606W exposure to allow cross-compare with CLEAR PSF ------------------------------------------------------------------------------------------------------------------------------------ 210 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 6 0.5 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 Comments: Expect flux of 2e6 e- per exposure over 1500 non-saturated stars. ------------------------------------------------------------------------------------------------------------------------------------ 220 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 2 1.0 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 230 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 4 0.7 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 240 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 2 1.0 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 250 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 4 0.8 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 260 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 2 1.0 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 270 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 4 2.0 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 280 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 2 1.0 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 290 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 4 10.0 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 300 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 2 1.0 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 9662( 2) - 06/27/02 13:48 - [ 6] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 310 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 4 25.0 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 320 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 4 1.0 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 330 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE, 2 0.5 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 340 NGC104 ACS/WF ACCUM WFC1 F606W CR-SPLIT=NO,PAREXP=NONE, 2 2.0 S C SIZEAXIS1=1024,SIZEAXIS2=1024, GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ 410 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 1 1.0 S C Comments: This, and remaining exps are full frame to allow derivation of a shutter shading correction. ------------------------------------------------------------------------------------------------------------------------------------ 420 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 1 0.5 S C Comments: This, and remaining exps are full frame to allow derivation of a shutter shading correction. ------------------------------------------------------------------------------------------------------------------------------------ 430 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 1 25.0 S C Comments: This, and remaining exps are full frame to allow derivation of a shutter shading correction. ------------------------------------------------------------------------------------------------------------------------------------ 440 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 1 1.0 S C Comments: This, and remaining exps are full frame to allow derivation of a shutter shading correction. ------------------------------------------------------------------------------------------------------------------------------------ 450 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 1 0.5 S C Comments: This, and remaining exps are full frame to allow derivation of a shutter shading correction. ------------------------------------------------------------------------------------------------------------------------------------ 460 NGC104 ACS/WF ACCUM WFC1 CLEAR CR-SPLIT=NO,PAREXP=NONE,GAIN=2 1 25.0 S C Comments: This, and remaining exps are full frame to allow derivation of a shutter shading correction. ------------------------------------------------------------------------------------------------------------------------------------ 9662( 2) - 06/27/02 13:48 - [ 7] Summary Form for Proposal 9662 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures HRC WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/HRC ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO PAREXP=NONE GAIN=2 SIZEAXIS2=1024 SIZEAXIS1=1024 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category CAL/ACS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ BETWEEN 15-JUL-2002 AND 31-OCT-2002 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements CLEAR F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC104 ------------------------------------------------------------------------------------------------------------------------------------