Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4012c Report Date: 09-May-96:19:03 Version: ********** Check-in Date: ********** 1.Proposal Title: DARK COUNT STATISTICS FOR GHRS DETECTORS ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID CAL/HRS Sub Category ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. Ronald Gilliland ST SCI USA ------------------------------------------------------------------------------------ 7. Abstract The proposed observations will obtain the statistical data needed to plan an operational strategy for observing faint targets with the GHRS. The proposed test involves only the use of Side 2, since only this side of the GHRS can benefit from the results of this test at the present time. Because of the loss of the GHRS low- resolution mode (G140L), many observing programs that had originally specified G140L have been changed to use G160M. Hence, the problem of reducing the GHRS dark-count becomes even more acute. The proposed tests should give us the information needed to evaluate by how much the dark-count can be reduced by the appropriate operational strategy (see Question 3). ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 0 par: 0 10. Num targs pri: 0 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4012c PI: Dr. Ronald Gilliland Proposal Title: DARK COUNT STATISTICS FOR GHRS DETECTORS ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Dr. Sara Heap NASA GSFC USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. Darkcount observations in "Rapid" and "Photoscan" modes are used. The "Rapid" observation provides lines of raw, unprocessed data every 0.35 seconds for the period of the exposure. This will provide statistical data on the distribution of bursts of counts produced by particle radiation. With these statistics, methods of noise removal can be evaluated. The "Photoscan" dark observation has the onboard data quality check enabled to discard every line of data that has more than one count total in the 0.2 second integration period. The data reported to the ground is the summation of all lines of data that had one or zero counts. This observation will provide the lowest darkcount that could be achieved with onboard data processing with very dim targets. The primary purpose of this proposal is to evaluate achievable darkcounts for Detector D1. Detector D2 observations have been included to allow similar measurements of that detector. Phosphor responses cause large differences in radiation effects. SEPTEMBER 1991 REVISION. This proposal has been modified so that it only uses Detector D2. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. Both observations must be scheduled based upon the location of the SAA. Evaluation of the data depends upon knowing the radiation environment. The "Rapid" observation needs to be started well before the entry into the SAA, to provide statistics during the quiet part of the orbit. This observation is scheduled to end in the SAA to allow evaluation of darkcount statistics as the radiation increases. The "Photoscan" observation is designed to measure ultimate achievable darkcount using onboard data processing and needs to be run in a quiet portion of the orbit. The "Photoscan" observation requires special handling to set the value of the OTFA (on-the-fly-adder) acceptance limit, FLYLIM. The default setting for FLYLIM is the maximum possible value of 33554431 to disable this feature. For this test the value of FLYLIM must be set to one to force rejection of all multiple count lines of data. Special scheduling requirements: 1. All observations use orbits which include SAA passages. 2. For the "Rapid" mode exposures, begin the observation 50 minutes before crossing the western boundry of the SAA. 3. For the "Photoscan" mode exposures, begin the observation 45 minutes after crossing the western boundry of the SAA. 4. Rejection of multiple count data in "Photoscan" observations will increase execution time by 20% of exposure time for Detector 1 and 50% of exposure time for Detector 2. No schedule adjustments are required since the only the last sub -exposures will be lost. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. ------------------------------------------------------------------------------------ 11. Address Information Page 3 Name: SARA HEAP Category: PI Institution: NASA GSFC Address: CODE 680 City: GREENBELT State: MD Zip Code: 20771 Country: USA Telephone: (301)286-5359 Telex (or e-mail): ------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4012c [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 50 DARK HRS RAPID 2.0 SAFE2 SAMPLE- 6 600S 5 1 CYCLE 2 / 50-60 TIME=0.35 Comments: START 50 MINUTES PRIOR TO SAA ENTRY ------------------------------------------------------------------------------------------------------------------------------------ 60 DARK HRS PHOTOSC NONE SAFE2 TYPE=SHORT-X 6 300S 5 1 AFTER 50 AN Comments: START 45 MINUTES AFTER SAA ENTRY SET FLYLIM=1 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4012c [ 5] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes RAPID PHOTOSCAN ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SAMPLE-TIME=0.35 TYPE=SHORT-X ------------------------------------------------------------------------------------------------------------------------------------ Proposal for CAL/HRS ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 2 / 50-60; AFTER 50; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements SAFE2 ------------------------------------------------------------------------------------------------------------------------------------ Target Names ------------------------------------------------------------------------------------------------------------------------------------