10252( 2) - 05/17/04 12:28 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 10252 Version: 2 Check-in Date: 17-May-2004 16:24:53 1.Proposal Title: Improving the Astrometric Calibration of ACS/WFC for the Most Useful Filters ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle 4. Parallel Pointing Tolerance GO 13 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Jay Anderson Rice University CoI: Dr. Ivan R. King University of Washington N ------------------------------------------------------------------------------------ 6. Abstract The distortion correction for the WFC, with which most ACS astrometry is done, is filter-dependent, and is not sufficiently accurate for the most useful filters to the community, F606W and F814W. We propose to derive improved corrections using 1 orbit for each filter. A by-product will be an astrometric standard field at the center of Omega Centauri. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will observe the center of Omega Cen with F606W and F814W in order to improve the distortion solution for these most useful filters. We will center the field on the inner calibration field. We'll take large offsets of (+600,+300) pixels or so in order to place the same stars in different places on the detector. Each orbit will do one of the filters and will have a short central exposure, and 5 long exposures, offset by (0, 0), (+600,+300), (- 300,+600), (-600,-300), and (300,-600). The net result of all the pos-targs will be a roughly circular field of view that will serve as an astrometric standard reference field. In order to make the field even more useful, we will compute proper motions for all the stars by means of archival data. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 10252( 2) - 05/17/04 12:28 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5139-ICF CALIBRATION, RA=13H27M8.0S +/- 1.0", DEC=- J2000 V = 3.68+/-0.1 ASTROMETRIC 47D30'10.0" +/- 1.0" (this is the integrated magnitude for the cluster; the central SB is 16.77 mags/sq arcsec) Coordinate Source: HST_IMAGE Comments: This position corresponds to the inner calibration field. We chose the ICF rather than the cluster center so that we could take deeper (and therefore more) exposures. If we had chosen the very core, many stars would be saturated and this would limit how many stars we could use for the calibration. The ICF has been well observed in the past, so we know there are plenty of stars that will have plenty of unsaturated signal in 340s. The cluster core is large enough that there isn't a significant gradient across the ACS field at this distance (about one core radiius). Also, the long baseline for observations of this field will allow for good proper motions so that the positions will be useful for years to come as an astrometric standard field. 10252( 2) - 05/17/04 12:28 - [ 3] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: This first orbit will do a pattern for the F606W filter and the second orbit for the F814W filter. The total pattern will map out a roughly circular region. We have unused visibility at the end of each orbit because we want our exposures to be as short as possible. 340s is as short as we can get them w/o incurring horrible overhead. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5139-ICF ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO,GAIN=2 1 15 S POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC5139-ICF ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO,GAIN=2 1 340 S POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC5139-ICF ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO,GAIN=2 1 340 S POS TARG 30, 15 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC5139-ICF ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO,GAIN=2 1 340 S POS TARG -15, 30 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC5139-ICF ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO,GAIN=2 1 340 S POS TARG -30,-15 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC5139-ICF ACS/WFC ACCUM WFCENTER F606W CR-SPLIT=NO,GAIN=2 1 340 S POS TARG 15,-30 ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC5139-ICF ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 15 S POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC5139-ICF ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 340 S POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC5139-ICF ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 340 S POS TARG 30,-15 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC5139-ICF ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 340 S POS TARG 15, 30 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC5139-ICF ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 340 S POS TARG -30, 15 ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC5139-ICF ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 340 S POS TARG -15,-30 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 01 1 none none none none 1 tbd 01 2 none none none none 1 tbd 01 3 none none none none 1 tbd 01 4 none none none none 1 tbd 01 5 none none none none 1 tbd 01 6 none none none none 1 tbd 01 7 none none none none 2 tbd 10252( 2) - 05/17/04 12:28 - [ 4] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 01 8 none none none none 2 tbd 01 9 none none none none 2 tbd 01 10 none none none none 2 tbd 01 11 none none none none 2 tbd 01 12 none none none none 2 tbd 10252( 2) - 05/17/04 12:28 - [ 5] Summary Form for Proposal 10252 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFCENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG 0, 0 POS TARG 30, 15 POS TARG -15, 30 POS TARG -30,-15 POS TARG 15,-30 POS TARG 30,-15 POS TARG 15, 30 POS TARG -30, 15 POS TARG -15,-30 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC5139-ICF ------------------------------------------------------------------------------------------------------------------------------------