! File: 2856C.PROP ! Database: PEPDB ! Date: 17-FEB-1994:18:42:39 coverpage: title_1: HST OBSERVATIONS OF PERIODIC COMETS: PART 2 sci_cat: SOLAR SYSTEM proposal_for: GO pi_title: DR. pi_fname: HAROLD pi_mi: A. pi_lname: WEAVER pi_inst: STSCI pi_country: USA pi_phone: 301-338-4765 keywords_1: COMET hours_pri: 4.53 num_pri: 1 wf_pc: X fos: X pi_position: DR. off_fname: H. off_mi: S. off_lname: STOCKMAN off_title: DEPUTY DIRECTOR off_inst: SPACE TELESCOPE SCIENCE INSTITUTE off_addr_1: 3700 SAN MARTIN DRIVE off_city: BALTIMORE off_state: MD off_zip: 21218 off_country: USA off_phone: 301-338-4730 ! end of coverpage abstract: line_1: The volatile composition of comets is a key diagnostic of cometary formation line_2: enviroments. The trace molecular composition of cometary nuclei, in particular, line_3: can be used to infer the physical and chemical state of the solar nebula or line_4: of the interstellar cloud from which the nebula condensed. Measuring these line_5: molecular abundances is extremely difficult due to the intrinsic weakness of line_6: the emissions from the trace species and can normally be attempted only on line_7: exceptionally bright comets. The advent of HST extends the feasibility of line_8: observing trace molecules to relatively faint, periodic comets. Thus, the line_9: compositions of "new" and "old" comets can be compared systematically. We line_10: propose using the FOS to obtain the volatile inventory in the brightest line_11: periodic comets appearing during the first HST GO cycle. Simultaneous UV and line_12: visible spectra will be used to measure the abundances of the important line_13: carbon-, nitrogen-, and sulfur-bearing species in the nucleus. Our highest line_14: priority target is Hartley-2. We also propose to observe Comet Wirtanen line_15: as part of the supplemental observing program. ! ! end of abstract general_form_proposers: lname: A'HEARN fname: MICHAEL title: DR. mi: F. inst: MARYLAND, UNIVERSITY OF country: USA ! lname: FELDMAN fname: PAUL title: DR. mi: D. inst: JOHNS HOPKINS UNIVERSITY country: USA ! lname: ARPIGNY fname: CLAUDE title: DR. inst: LIEGE UNIVERSITY country: BELGIUM esa: X ! lname: WEAVER fname: HAROLD title: P.I. mi: A. inst: STSCI country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: We estimate that this program will require 20 separate visits line_2: to the comet. During the first visit we will take a WFC image line_3: to assess the amount of ``zero-point'' ephemeris error. line_4: We expect to use FOS Onboard Acquisitions line_5: (FOS ACQ/FIRMWARE is preferred) on subsequent orbits. line_6: After obtaining the WFC image, operations for all subsequent orbits line_7: will consist of the following steps: line_8: (1) Acquire GS's in COARSE TRACK mode. line_9: (2) Use FOS Onboard Acquisition to center the comet nucleus in one line_10: of the 1" square apertures to an accuracy better than 0.25". line_11: (3) A long exposure (as long as the orbit window allows) is taken line_12: through whatever grating is appropriate for the wavelength range line_13: being sampled in that orbit. line_14: (5) Since the target will be moving relatively slow (about 0.05"/sec) line_15: we expect that a single GS pair will support observations line_16: for an entire observability window. Since the motion is primarily line_17: along the ecliptic (i.e., along the long dimension of FGS's 1 and line_18: 3), a single GS pair may support observations of this comet line_19: for several orbits. ! question: 6 section: 1 line_1: We note that the success of our acquisition strategy line_2: depends on the feasibility of FOS Onboard Acquisition for comets. line_3: Since the FOS signal during acquisition should consist primarily of line_4: continuum radiation from cometary grains, the spatial brightness line_5: distribution should be strongly peaked toward the nucleus, line_6: and the FOS centering algorithm should accurately centroid the line_7: nucleus. line_8: However, if FOS Onboard Acq. fails, then we must devise an line_9: alternate strategy. ! question: 8 section: 1 line_1: The comets originally selected as targets in this line_2: program are no longer available due to the HST line_3: launch slip. Thus, we have searched for and have identified line_4: three new comets as possible candidates line_5: in our supplemental observing program (2856): Wirtanen (1985q), line_6: Machholz (1986 VIII), and P/Faye. Wirtanen and Machholz line_7: have similar brightnesses, and each is about a factor of four line_8: brighter than Faye. (Faye was considered because it is the target line_9: of another GO program and we thought that we might be able to provide line_10: some supporting science for that program.) Since Wirtanen has a longer line_11: observability window than Machholz, we are listing Wirtanen as line_12: the target for program 2856. ! !end of general form text general_form_address: lname: WEAVER fname: HAROLD mi: A. title: DR. category: PI inst: SPACE TELESCOPE SCIENCE INSTITUTE addr_1: 3700 SAN MARTIN DR. city: BALTIMORE state: MD zip: 21218 country: USA ! lname: WEAVER fname: HAROLD mi: A title: DR. category: PI inst: SPACE TELESCOPE SCIENCE INSTITUTE addr_1: 3700 SAN MARTIN DRIVE city: BALTIMORE state: MD zip: 21218 phone: (301) 338-4765 telex: 684-9109-STSCI 411 ! ! end of general_form_address records ! No fixed target records found solar_system_targets: targnum: 1 name_1: WIRTANEN descr_1: COMET WIRTANEN lev1_1: STD = WIRTANEN, lev1_2: ACQ = 0.25 wind_1: RANGE WIRTANEN SUN LT 1.1 wind_2: RANGE WIRTANEN EARTH LT 1.4 comment_1: OPTIMUM OBSERVING TIME IS NEAR comment_2: PERIHELION. NOMINAL PERIHELION DATE comment_3: IS 9/21/91 BUT WILL NEED UPDATING comment_4: AFTER THE COMET IS RECOVERED. comment_5: TOTAL COMA VISUAL MAGNITUDE SHOULD comment_6: BE ABOUT 10 DURING THE TIME OF comment_7: OBSERVATIONS. LAST PERIHELION WAS IN comment_8: 1985 (1985 Q). fluxnum_1: 1 fluxval_1: SURF(V) = 15 +/- 1 fluxnum_2: 2 fluxval_2: SURF-LINE(4315) = 2.5 +/- 1.2 E-15 fluxnum_3: 3 fluxval_3: W-LINE(4315) = 0.029 fluxnum_4: 4 fluxval_4: SURF-LINE(5730) = 2 +/- 1 E-15 fluxnum_5: 5 fluxval_5: W-LINE(5730) = 0.038 fluxnum_6: 6 fluxval_6: SURF-LINE(1478) = 2 +/- 1 E-14 fluxnum_7: 7 fluxval_7: W-LINE(1478) = 0.0099 fluxnum_8: 8 fluxval_8: SURF-LINE(2957) = 1.5 +/- 0.7 E-14 fluxnum_9: 9 fluxval_9: W-LINE(2957) = 0.020 fluxnum_10: 10 fluxval_10: SIZE = 1 ! ! end of solar system targets ! No generic target records found exposure_logsheet: linenum: 1.000 sequence_1: DEFINE sequence_2: IMAGE targname: WIRTANEN config: WFC opmode: IMAGE aperture: ALL sp_element: F791W num_exp: 1 time_per_exp: 40 S fluxnum_1: 1 fluxnum_2: 10 comment_1: A WFC IMAGE IS USED TO comment_2: ESTIMATE THE ZERO-PT comment_3: POINTING ERROR. ! linenum: 2.000 sequence_1: DEFINE sequence_2: ACQ-BLUE targname: WIRTANEN config: FOS/BL opmode: ACQ/FIRMWARE aperture: 4.3 sp_element: MIRROR num_exp: 1 time_per_exp: 200 S comment_1: FOS/BL ONBOARD ACQ EXP. comment_2: THE PSEUDO IMAGE WILL BE comment_3: USED TO VERIFY POINTING. ! linenum: 3.000 sequence_1: DEFINE sequence_2: ACQ-RED targname: WIRTANEN config: FOS/RD opmode: ACQ/FIRMWARE aperture: 4.3 sp_element: MIRROR num_exp: 1 time_per_exp: 40 S comment_1: FOS/RD ONBOARD ACQ EXP. comment_2: THE PSEUDO IMAGE WILL BE comment_3: USED TO VERIFY POINTING. ! linenum: 4.000 sequence_1: DEFINE sequence_2: S2 targname: WIRTANEN config: FOS/BL opmode: ACCUM aperture: 1.0-PAIR sp_element: G270H wavelength: 2230-3309 num_exp: 1 time_per_exp: 16 M s_to_n: 6 s_to_n_time: 1 H fluxnum_1: 8 fluxnum_2: 9 fluxnum_3: 10 priority: 1 param_1: STEP-PATT=SINGLE comment_1: ASSUMES NOMINAL VIS WINDOW OF 45M. comment_2: EXP TIME MUST BE SCALED IF WINDOW comment_3: IS LONGER OR SHORTER. IF GS comment_4: PAIR IS LOST DURING WINDOW THEN comment_5: SWITCH TO GYROHOLD FOR REST OF comment_6: WINDOW. ASSUME S2/H2O IS 0.01%. ! linenum: 5.000 sequence_1: DEFINE sequence_2: CH targname: WIRTANEN config: FOS/RD opmode: ACCUM aperture: 1.0-PAIR sp_element: G400H wavelength: 3240-4787 num_exp: 1 time_per_exp: 16 M s_to_n: 4 s_to_n_time: 30 M fluxnum_1: 2 fluxnum_2: 3 fluxnum_3: 10 priority: 2 param_1: STEP-PATT=SINGLE comment_1: ASSUMES NOMINAL VIS WINDOW OF 45M. comment_2: EXP TIME MUST BE SCALED IF WINDOW comment_3: IS LONGER OR SHORTER. IF GS comment_4: PAIR IS LOST DURING WINDOW THEN comment_5: SWITCH TO GYROHOLD FOR REST OF comment_6: WINDOW. ASSUME CH4/H2O IS 1%. ! linenum: 6.000 sequence_1: DEFINE sequence_2: CO targname: WIRTANEN config: FOS/BL opmode: ACCUM aperture: 1.0-PAIR sp_element: G130H wavelength: 1150-1608 num_exp: 1 time_per_exp: 16 M s_to_n: 3 s_to_n_time: 1 H fluxnum_1: 6 fluxnum_2: 7 fluxnum_3: 10 priority: 3 param_1: STEP-PATT=SINGLE comment_1: ASSUMES NOMINAL VIS WINDOW OF 45M. comment_2: EXP TIME MUST BE SCALED IF WINDOW comment_3: IS LONGER OR SHORTER. IF GS comment_4: PAIR IS LOST DURING WINDOW THEN comment_5: SWITCH TO GYROHOLD FOR REST OF comment_6: WINDOW. ASSUME CO/H2O IS 5%. ! linenum: 7.000 sequence_1: DEFINE sequence_2: NH2 targname: WIRTANEN config: FOS/RD opmode: ACCUM aperture: 1.0-PAIR sp_element: G570H wavelength: 4566-6817 num_exp: 1 time_per_exp: 16 M s_to_n: 4 s_to_n_time: 30 M fluxnum_1: 4 fluxnum_2: 5 fluxnum_3: 10 priority: 1 param_1: STEP-PATT=SINGLE comment_1: ASSUMES NOMINAL VIS WINDOW OF 45M. comment_2: EXP TIME MUST BE SCALED IF WINDOW comment_3: IS LONGER OR SHORTER. IF GS comment_4: PAIR IS LOST DURING WINDOW THEN comment_5: SWITCH TO GYROHOLD FOR REST OF comment_6: WINDOW. ASSUME B(NH2)=B(CH). ! linenum: 8.000 sequence_1: USE sequence_2: IMAGE ! linenum: 9.000 sequence_1: USE sequence_2: ACQ-BLUE req_1: ONBOARD ACQ FOR 10; req_2: SEQ 8-10 NON-INT; ! linenum: 10.000 sequence_1: USE sequence_2: S2 ! linenum: 10.100 sequence_1: USE sequence_2: IMAGE ! linenum: 10.200 sequence_1: USE sequence_2: ACQ-BLUE req_1: ONBOARD ACQ FOR 10.3; req_2: SEQ 10.1-10.3 NON-INT; ! linenum: 10.300 sequence_1: USE sequence_2: S2 ! linenum: 11.000 sequence_1: USE sequence_2: IMAGE ! linenum: 12.000 sequence_1: USE sequence_2: ACQ-BLUE req_1: ONBOARD ACQ FOR 13; req_2: SEQ 11-13 NON-INT; ! linenum: 13.000 sequence_1: USE sequence_2: S2 ! linenum: 14.000 sequence_1: USE sequence_2: IMAGE ! linenum: 15.000 sequence_1: USE sequence_2: ACQ-BLUE req_1: ONBOARD ACQ FOR 16; req_2: SEQ 14-16 NON-INT; ! linenum: 16.000 sequence_1: USE sequence_2: S2 ! linenum: 17.000 sequence_1: USE sequence_2: IMAGE ! linenum: 18.000 sequence_1: USE sequence_2: ACQ-BLUE req_1: ONBOARD ACQ FOR 19; req_2: SEQ 17-19 NON-INT; ! linenum: 19.000 sequence_1: USE sequence_2: S2 ! linenum: 20.000 sequence_1: USE sequence_2: IMAGE ! linenum: 21.000 sequence_1: USE sequence_2: ACQ-BLUE req_1: ONBOARD ACQ FOR 22; req_2: SEQ 20-22 NON-INT; ! linenum: 22.000 sequence_1: USE sequence_2: S2 ! ! end of exposure logsheet ! No scan data records found