! File: 3368C.PROP ! Database: PEPDB ! Date: 19-FEB-1994:05:11:31 coverpage: title_1: K FACTOR ADJUSTMENT TEST proposal_for: ENG/AST pi_title: DR. pi_fname: FRANCIS pi_mi: H. pi_lname: SCHIFFER pi_inst: STSCI pi_country: USA pi_phone: (301)338-4789 hours_pri: 0.56 num_pri: 5 fgs: Y ! end of coverpage abstract: line_1: The performance of the FGSs in acquiring and holding faint guide line_2: stars in fine lock is worse than the pre-launch expectations. line_3: As result guide stars, which are usable in fine lock, are not available line_4: over much of the sky in the density that is necessary. In addition, line_5: the characteristics of the FGS transfer functions differ from the line_6: pre-launch assumptions in ways which affect the selection of the line_7: K-factors, which control how the FGS works. line_8: Dr. L. G. Taff has developed a simulation of the FGS walkdown and line_9: fine lock algorithms that are implemented in the flight software line_10: and hardware to investigate the effect of the transfer functions on line_11: the selection of values for the K-factors. With this simulation, line_12: he has shown that it is possible to chose K-factors that will line_13: improve the performance of the FGS particularly for faint stars. line_14: Prior to using these new values with scientific observations, the line_15: validity of the model and the new K-factors must be demonstrated. line_16: This test performs that verification. ! ! end of abstract general_form_proposers: lname: TAFF fname: LAURENCE title: DR. mi: G. inst: STSCI country: USA ! lname: LUPIE fname: OLIVIA title: DR. mi: L. inst: STSCI country: USA ! lname: SCHIFFER fname: FRANCIS title: DR. mi: H. inst: STSCI country: USA ! lname: SCHIFFER fname: FRANCIS title: DR. mi: H. inst: STSCI country: USA ! ! end of general_form_proposers block general_form_text: question: 2 section: 1 line_1: The single biggest problem with guide star selection at this time line_2: is the lack of stars brighter than the faint limit for fine lock line_3: guidance. The current faint limit of the FGSs is approximately line_4: 1.5 magnitudes brighter than was originally planned. Extending line_5: the usable guide stars to 1 or 2 magnitudes fainter would resolve line_6: most of this problem. line_7: The simulations done by Dr. L. G. Taff predict that changes line_8: in the K-factors, which control the FGS, would yield substantial line_9: gains in the ability of the FGS to acquire and track faint stars. line_10: Demonstrating that the flight hardware can achieve these predicted line_11: gains would allow the use of fainter guide stars during normal line_12: operations. The ability to use fainter guide stars would allow line_13: a wider range of scientific problems to be undertaken with the HST. line_14: If the validity of the predictions is not determined, new K-factors line_15: could not be installed in the operational system without seriously line_16: jeoparizing the current scientific mission of HST. Only testing of line_17: the new K-factors in a controlled manner can demonstrate that the line_18: model is correct and the performance can be improved without risking line_19: the science. ! question: 3 section: 1 line_1: Three distinct sets of observations are necessary to validate line_2: the simulations done by Dr. L.G.Taff. line_4: 1. observe a set of stars using transfer mode to identify stars line_5: which are single and have acceptable transfer functions. Without line_6: these observations it would be impossible to tell if the problems line_7: were caused by the star or the K-factors. line_9: 2. using a star which was selected from the list of stars observed line_10: with the transfer mode, perform a series of acquisitions/observations line_11: using the astrometer in POSITION mode. Repeat the measurements for a line_12: sufficent number of times to determine the likelihood of success. line_13: These observations need to be done with the standard K-factors and are line_14: the control (ie current baseline). line_16: 3. using the same star as step 2, perform a series of standard line_17: astrometry POSITION mode observations using K-factors that the simulation line_18: predicts would yield a higher success rate. Sufficent observations are line_19: needed to determine the likelihood of successful acquisition. ! question: 3 section: 2 line_1: TRANSFORMATION REQUIREMENTS - line_2: The observations should be done with coarse track guiding on the FGS's. line_3: The early acquisition observations (line 10) should be done with a line_4: single set of guide stars unless no such pair exists. Acquisitions line_5: should only use a single pair in coarse track. line_7: SCHEDULING REQUIREMENTS - line_8: The observations from part 1 will be used to determine the target to line_9: be used for parts 2 and 3. The target given in lines 20-22 is a place line_10: keeper. It is expected that when the part 1 observations are analyzed, line_11: the coordinates of target 10 (used by lines 20-22) will be updated, line_12: new guide stars requested and the observation rescheduled. line_14: COMMANDING REQUIREMENTS - line_15: Lines 20 and 21 will use standard astrometry commanding. line_16: Line 22 will require special commanding which modifies the K-factors line_17: as per the results of the simulations; K1 and Kz will be modified. line_18: The values will remain constant for all the data collected from line 22. line_19: For the standard observations the K-factors should be on the order of line_20: Kz=0.00704, K1x=0.033 and K1y=0.041 (values for a 13.0 mag star). line_21: For special commanding, the K-factors should be Kz=0.00417, line_22: K1x=0.0162 and K1y=0.0158. line_23: All K-factors are expressed in engineering units. ! question: 4 section: 1 line_1: Tests of the performance flight hardware and software cannot be done line_2: with anything less that the actual HST. ! question: 5 section: 1 line_1: The observations were chosen to be as short as possible and still line_2: enable us to verify the acquisition of fine lock. It is necessary to line_3: determine both the position of the null and the position of each fine line_4: lock in order to determine if a "false" lock was achieved. line_6: The initial transfer scans are necessary to prevent wasting all of the line_7: remaining time by attempting the measurements on a star which will not line_8: give good statitics because of the star. Five stars will ensure that line_9: one of them is usable even if the double star probability is as large line_10: as 70 percent. ! question: 6 section: 1 line_1: The Observations from line 10 must be scheduled sufficiently before line_2: lines 20-22 to allow us to plot the transfer functions and determine line_3: the best star for the test. The analysis will provide an updated line_4: position for target 10 TEST_STAR. SPSS is expected to enter the line_5: updated position into the target, request new guide stars and reschedule line_6: the observations. line_8: The special commanding needed for line 22 will require a special line_9: commanding instruction and the attachment of that instruction to the line_10: observations. line_12: Observations should be done with coarse track guiding. A single pair line_13: of stars for the acquisition scenario is acceptable. ! question: 7 section: 1 line_1: The observations will be extracted with OMS. The success or failure line_2: will be determined by the FGS Data Valid telemetry flag. In addition line_3: the position of the star will be determined from the star selector line_4: position data. The repeatability of the observations will be line_5: determined by comparing the positions determined from each observation. ! question: 8 section: 1 line_1: ! question: 9 section: 1 line_1: Proposal 3110 - Coarse Track Performance ! question: 10 section: 1 line_1: OMS which will be used to extract the data. line_2: Workstations and computational support to analyze the data. ! !end of general form text general_form_address: lname: SCHIFFER fname: FRANCIS mi: H. category: PI inst: STSCI ! lname: ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: STAR-1 name_2: GSC89240671 descr_1: FAINT STAR FOR FGS TESTING. pos_1: RA = 8H 0M 49.662S +/- 0.1S, pos_2: DEC = -60D 24' 27.82" +/- 0.5" equinox: J2000 pos_epoch_bj: J pos_epoch_yr: 2000.00 comment_1: TO BE CHECKED FOR DUPLICITY. fluxnum_1: 1 fluxval_1: V = 13.33 +/- 0.2 ! targnum: 2 name_1: STAR-2 name_2: GSC89241250 descr_1: FAINT STAR FOR FGS TESTING. pos_1: RA = 8H 0M 32.729S +/- 0.1S, pos_2: DEC = -60D 23' 54.26" +/- 0.5" equinox: J2000 pos_epoch_bj: J pos_epoch_yr: 2000.00 comment_1: TO BE CHECKED FOR DUPLICITY. fluxnum_1: 1 fluxval_1: V = 13.22 +/- 0.2 ! targnum: 3 name_1: STAR-3 name_2: GSC89240303 descr_1: FAINT STAR FOR FGS TESTING. pos_1: RA = 8H 0M 19.972S +/- 0.1S, pos_2: DEC = -60D 24' 31.61" +/- 0.5" equinox: J2000 pos_epoch_bj: J pos_epoch_yr: 2000.00 comment_1: TO BE CHECKED FOR DUPLICITY. fluxnum_1: 1 fluxval_1: V = 13.76 +/- 0.2 ! targnum: 4 name_1: STAR-4 name_2: GSC89240772 descr_1: FAINT STAR FOR FGS TESTING. pos_1: RA = 8H 1M 20.498S +/- 0.1S, pos_2: DEC = -60D 24' 51.09" +/- 0.5" equinox: J2000 pos_epoch_bj: J pos_epoch_yr: 2000.00 comment_1: TO BE CHECKED FOR DUPLICITY. fluxnum_1: 1 fluxval_1: V = 13.86 +/- 0.2 ! targnum: 5 name_1: STAR-5 name_2: GSC89241088 descr_1: FAINT STAR FOR FGS TESTING. pos_1: RA = 8H 1M 3.068S +/- 0.1S, pos_2: DEC = -60D 26' 50.95" +/- 0.5" equinox: J2000 pos_epoch_bj: J pos_epoch_yr: 2000.00 comment_1: TO BE CHECKED FOR DUPLICITY. fluxnum_1: 1 fluxval_1: V = 13.89 +/- 0.2 ! targnum: 10 name_1: TEST-STAR descr_1: FAINT STAR FOR FGS TESTING. descr_2: TESTED TO BE SINGLE BY FGS TRANS MODE. pos_1: RA = 8H 0M 49.662S +/- 0.1S, pos_2: DEC = -60D 24' 27.82" +/- 0.5" equinox: J2000 pos_epoch_bj: J pos_epoch_yr: 2000.00 comment_1: COORDINATES WILL BE UPDATED comment_2: AFTER THE TRANSFER SCANS comment_3: ARE COMPLETED. fluxnum_1: 1 fluxval_1: V = 13.33 +/- 0.2 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 10.000 targname: STAR-1 config: FGS opmode: TRANS aperture: 2 sp_element: PUPIL num_exp: 1 time_per_exp: 250S priority: 1 param_1: SCANS=5 req_1: DO FOR TARGETS 1-5; req_2: GUID TOL 0.030" /10-22; req_3: EARLY ACQ FOR 20-22; req_4: CYCLE 0 /10-22; comment_1: TRANSFER SCANS TO CHECK FOR DUPLICITY; comment_2: GUIDING DONE IN COARSE TRACK; ! linenum: 20.000 targname: STAR-2 config: FGS opmode: TRANS aperture: 2 sp_element: PUPIL num_exp: 1 time_per_exp: 250S priority: 1 param_1: SCANS=5 req_1: SEQ 20-22 NO GAP; comment_1: MEASURE NULL LOCATION. ! linenum: 21.000 targname: STAR-2 config: FGS opmode: POS aperture: 2 sp_element: PUPIL num_exp: 24 time_per_exp: 25S priority: 1 param_1: DATA-RATE=32 comment_1: MEASURE ACQ PROBABILITY. comment_2: USE STANDARD ASTROMETRY CMDING. ! linenum: 22.000 targname: STAR-2 config: FGS opmode: POS aperture: 2 sp_element: PUPIL num_exp: 32 time_per_exp: 25S priority: 1 param_1: DATA-RATE=32 comment_1: MEASURE ACQ PROBABILITY. comment_2: USE REVISED K-FACTORS. comment_3: KZ=0.00417 comment_4: K1X=0.0162, K1Y=0.0158 comment_5: K-FACTORS IN ENG. UNITS. ! ! end of exposure logsheet ! No scan data records found