! File: 4012C.PROP ! Database: PEPDB ! Date: 20-FEB-1994:03:45:41 coverpage: title_1: DARK COUNT STATISTICS FOR GHRS DETECTORS proposal_for: CAL/HRS pi_title: DR. pi_fname: RONALD pi_lname: GILLILAND pi_inst: ST SCI pi_country: USA hrs: Y ! end of coverpage abstract: line_1: The proposed observations will obtain the statistical data line_2: needed to plan an operational strategy for observing faint line_3: targets with the GHRS. The proposed test involves only the line_4: use of Side 2, since only this side of the GHRS can benefit line_5: from the results of this test at the present time. line_7: Because of the loss of the GHRS low-resolution mode (G140L), line_8: many observing programs that had originally specified G140L line_9: have been changed to use G160M. Hence, the problem of reducing line_10: the GHRS dark-count becomes even more acute. The proposed tests line_11: should give us the information needed to evaluate by how much line_12: the dark-count can be reduced by the appropriate operational line_13: strategy (see Question 3). ! ! end of abstract general_form_proposers: lname: HEAP fname: SARA title: DR. inst: NASA GSFC country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: Darkcount observations in "Rapid" and "Photoscan" modes are used. The line_2: "Rapid" observation provides lines of raw, unprocessed data every 0.35 line_3: seconds for the period of the exposure. This will provide statistical data line_4: on the distribution of bursts of counts produced by particle radiation. line_5: With these statistics, methods of noise removal can be evaluated. The line_6: "Photoscan" dark observation has the onboard data quality check enabled to line_7: discard every line of data that has more than one count total in the line_8: 0.2 second integration period. The data reported to the ground is the line_9: summation of all lines of data that had one or zero counts. This line_10: observation will provide the lowest darkcount that could be achieved with line_11: onboard data processing with very dim targets. line_13: The primary purpose of this proposal is to evaluate achievable darkcounts line_14: for Detector D1. Detector D2 observations have been included to allow line_15: similar measurements of that detector. Phosphor responses cause large line_16: differences in radiation effects. line_18: SEPTEMBER 1991 REVISION. This proposal has been modified so that line_19: it only uses Detector D2. ! question: 5 section: 1 line_1: Both observations must be scheduled based upon the location of the SAA. line_2: Evaluation of the data depends upon knowing the radiation environment. The line_3: "Rapid" observation needs to be started well before the entry into the SAA, line_4: to provide statistics during the quiet part of the orbit. This observation line_5: is scheduled to end in the SAA to allow evaluation of darkcount statistics line_6: as the radiation increases. The "Photoscan" observation is designed to line_7: measure ultimate achievable darkcount using onboard data processing and line_8: needs to be run in a quiet portion of the orbit. line_10: The "Photoscan" observation requires special handling to set the value of line_11: the OTFA (on-the-fly-adder) acceptance limit, FLYLIM. The default setting line_12: for FLYLIM is the maximum possible value of 33554431 to disable this line_13: feature. For this test the value of FLYLIM must be set to one to force line_14: rejection of all multiple count lines of data. line_16: Special scheduling requirements: line_18: 1. All observations use orbits which include SAA passages. line_20: 2. For the "Rapid" mode exposures, begin the observation 50 minutes line_21: before crossing the western boundry of the SAA. ! question: 5 section: 2 line_1: 3. For the "Photoscan" mode exposures, begin the observation 45 minutes line_2: after crossing the western boundry of the SAA. line_4: 4. Rejection of multiple count data in "Photoscan" observations will line_5: increase execution time by 20% of exposure time for Detector 1 and line_6: 50% of exposure time for Detector 2. No schedule adjustments are line_7: required since the only the last sub-exposures will be lost. ! question: 6 section: 1 line_1: ! !end of general form text general_form_address: lname: HEAP fname: SARA title: DR. category: PI inst: NASA GSFC addr_1: CODE 680 city: GREENBELT state: MD zip: 20771 country: USA phone: (301)286-5359 ! ! end of general_form_address records ! No fixed target records found ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 50.000 targname: DARK config: HRS opmode: RAPID aperture: 2.0 sp_element: SAFE2 num_exp: 6 time_per_exp: 600S s_to_n: 5 priority: 1 param_1: SAMPLE-TIME=0.35 req_1: CYCLE 2 / 50-60; comment_1: START 50 MINUTES PRIOR TO comment_2: SAA ENTRY ! linenum: 60.000 targname: DARK config: HRS opmode: PHOTOSCAN aperture: NONE sp_element: SAFE2 num_exp: 6 time_per_exp: 300S s_to_n: 5 priority: 1 param_1: TYPE=SHORT-X, req_1: AFTER 50; comment_1: START 45 MINUTES AFTER comment_2: SAA ENTRY comment_3: SET FLYLIM=1 ! ! end of exposure logsheet ! No scan data records found