! File: 2925C.PROP ! Database: PEPDB ! Date: 17-FEB-1994:22:10:00 coverpage: title_1: GHRS SKY BACKGROUND proposal_for: SV/HRS pi_title: DR. pi_fname: FREDRICK pi_lname: WALTER pi_inst: SUNY pi_country: USA pi_phone: (516)632-8232 hours_pri: 0.26 num_pri: 2 hrs: Y pi_position: ASSISTANT PROF. ! end of coverpage abstract: line_1: Ground based calibration of the GHRS target acquisition mirrors line_2: and measured intensities of geocoronal Lyman alpha emission line_3: lead to the prediction that mirror N2 will detect anywhere line_4: from 6 to 300 counts per second, depending on the viewing line_5: geometry and solar activity. This OV/SV test is designed to line_6: measure the background and to calibrate the parameters in a line_7: simple model of its intensity. ! ! end of abstract general_form_proposers: lname: WALTER fname: FREDRICK title: DR. inst: SUNY country: USA ! lname: EBBETS fname: DENNIS title: DR. inst: BASG country: USA ! ! end of general_form_proposers block general_form_text: question: 2 section: 1 line_1: There are at least 5 targets in the GHRS Cycle 0 GTO line_2: program which may be faint enough to be troubled by sky line_3: background light during target acquisition. We request line_4: that this test be performed to help calibrate the actual line_5: GHRS sensitivity to geocoronal Lyman alpha emission, the line_6: primary source of background. We will observe the back line_7: ground in the N2 acquisition mode, and scale the results line_8: to the other mirrors. ! question: 3 section: 1 line_1: The observation consists of a "flux measurement" with line_2: mirror N2, followed by a 2 minute spectrum exposure of line_3: Lyman alpha (1216 A) with grating G160M. This pair will line_4: be repeated for a total of 7 times. The target is a dark line_5: nebula, which ensures that no starlight is entering the line_6: GHRS. The target is large enough to have very wide line_7: pointing and guiding tolerances, allowing the obsevation line_8: to be done under gyro control. The first target is at high line_9: declination to allow a long period of visibility during line_10: one orbit, and to avoid passages through the SAA. The line_11: acquisition exposure will measure the response of N2 to line_12: the sky background, while the spectrum will isolate the line_13: flux of Lyman alpha light. The repeats will measure the line_14: background as a function of zenith angle over a large line_15: fraction of a target's visibility. The delta plan test line_16: with the second target provides a larger variation in both line_17: the solar and detector zenith angles, and will allow a line_18: more complete parameterization of the spatial and temporal line_19: dependence of the sky brightness. ! question: 5 section: 1 line_1: Count rates are based on a 1 kR Ly alpha intensity. The line_2: actual intensity may be anywhere between 1 and 50 kR. The line_3: stated exposure times will give adequate detection at the line_4: faint end, but will not cause overexposure at the bright line_5: end. The RPSS Resource Estimator was used to estimate line_6: 7.61 minutes of spacecraft time for the two exposures. line_7: Measurements at 7 zenith angles require 53.27 minutes. line_8: We have requested that they be grouped within 60 minutes. ! question: 6 section: 1 line_1: We request that this test be run during OV part 2, or as line_2: early in SV as possible. The first execution should be a line_3: minimum plan activity. The second measurement several line_4: months later at a different viewing geometry may be a line_5: delta plan test. ! question: 7 section: 1 line_1: 1. Calibrate sensitivity of mirror N2 to sky background line_2: 2. Calibrate variation of Ly alpha intensity with line_3: spacecraft zenith angle and solar zenith angle. line_4: 3. Advise GTOs of potential difficulties. Recommend line_5: alternative acquisition strategies or time require- line_6: ments (eg dark time) if necessary. line_7: 4. Design enhancements to the GHRS target acqusition line_8: flight software to suppress contamination problems, line_9: if found to be significant. ! question: 8 section: 1 line_1: For the minimum plan exposures, lines 103-109, either line_2: target L1400 or L1251A may be used with no change to line_3: the exposure specification. Similarly for the delta line_4: plan exposures, lines 117 - 121, either L260 or B35 line_5: may be used. line_7: The observations may be made under gyro guiding. We line_8: would like the observation to begin with the target line_9: just rising above the limb of the earth, to measure line_10: the widest possible range of spacecraft zenith angles. ! !end of general form text general_form_address: lname: WALTER fname: FREDERICK title: DR. category: PI ! lname: WALTER fname: FREDRICK title: DR. category: PI inst: SUNY addr_1: ASTRONOMY PROGRAM, ROOM 255 addr_2: DEPT. EARTH & SPACE SCIENCES addr_3: STATE UNIVERSITY OF NEW YORK city: STONY BROOK state: NY zip: 11794 country: USA phone: (516) 632-8232 ! lname: EBBETS fname: DENNIS title: DR. category: CON inst: BASG addr_1: BALL AEROSPACE SYSTEMS GROUP addr_2: PO BOX 1062 addr_3: MAIL STOP AR1 city: BOULDER state: CO zip: 80306 country: USA phone: (303) 939-5964 ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: L1400 descr_1: EXTENDED DARK NEBULA pos_1: RA=04H 26M 40S +/- 15S, pos_2: DEC=+54D 47' 00" +/- 1" equinox: 1950 pm_or_par: N fluxnum_1: 1 fluxval_1: SURF(1216)=4+/-1E-14 ! targnum: 2 name_1: L1251A descr_1: EXTENDED DARK NEBULA pos_1: RA=22H 28M 15S +/- 15S, pos_2: DEC=+74D 59' 00" +/- 1" equinox: 1950 pm_or_par: N fluxnum_1: 1 fluxval_1: SURF(1216)=4+/-1E-14 ! targnum: 3 name_1: B35 descr_1: EXTENDED DARK NEBULA pos_1: RA=05H 41M 46S +/- 15S, pos_2: DEC=+09D 09' 00" +/- 1" equinox: 1950 pm_or_par: N fluxnum_1: 1 fluxval_1: SURF(1216)=4+/-1E-14 ! targnum: 4 name_1: L260 descr_1: EXTENDED DARK NEBULA pos_1: RA=16H 44M 35S +/- 15S, pos_2: DEC=-09D 32' 00" +/- 1" equinox: 1950 pm_or_par: N fluxnum_1: 1 fluxval_1: SURF(1216)=4+/-1E-14 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 101.000 sequence_1: DEF sequence_2: SKY targname: # config: HRS opmode: ACQ aperture: 2.0 sp_element: MIRROR-N2 num_exp: 1 time_per_exp: 12.75S s_to_n: 9 fluxnum_1: 1 priority: 1 param_1: SEARCH-SIZE=1, param_2: LOCATE=NO req_1: ONBOARD ACQ FOR 102; req_2: SEQ 101-102 NO GAP; req_3: CYCLE 0/ 101-121; ! linenum: 102.000 sequence_1: ^ targname: ^ config: ^ opmode: ACCUM aperture: ^ sp_element: G160M wavelength: 1216 num_exp: 1 time_per_exp: 2M s_to_n: 15 fluxnum_1: 1 priority: 1 param_1: STEP-PATT=2 ! linenum: 103.000 sequence_1: USE sequence_2: SKY targname: L1251A req_1: GUID TOL 10"/103-109; req_2: GROUP 103-109 WITHIN 60M ! linenum: 104.000 sequence_1: ^ sequence_2: ^ targname: ^ ! linenum: 105.000 sequence_1: ^ sequence_2: ^ targname: ^ ! linenum: 106.000 sequence_1: ^ sequence_2: ^ targname: ^ ! linenum: 107.000 sequence_1: ^ sequence_2: ^ targname: ^ ! linenum: 108.000 sequence_1: ^ sequence_2: ^ targname: ^ ! linenum: 109.000 sequence_1: ^ sequence_2: ^ targname: ^ ! linenum: 117.000 sequence_1: USE sequence_2: SKY targname: B35 req_1: GUID TOL 10"/117-121; req_2: GROUP 117-121 WITHIN 48M; req_3: COND IF SV DELTA PLAN ! linenum: 118.000 sequence_1: ^ sequence_2: ^ targname: ^ req_1: COND IF SV DELTA PLAN ! linenum: 119.000 sequence_1: ^ sequence_2: ^ targname: ^ req_1: COND IF SV DELTA PLAN ! linenum: 120.000 sequence_1: ^ sequence_2: ^ targname: ^ req_1: COND IF SV DELTA PLAN ! linenum: 121.000 sequence_1: ^ sequence_2: ^ targname: ^ req_1: COND IF SV DELTA PLAN ! ! end of exposure logsheet ! No scan data records found