Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 2657c Report Date: 09-May-96:17:16 Version: ********** Check-in Date: ********** 1.Proposal Title: HIGH RESOLUTION SPECTROSCOPY OF COMETS ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID SOLAR SYSTEM GO Sub Category COMET ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone P.i. Michael F. A'hearn MARYLAND, UNIVERSITY OF USA 301-454-6076 PROFESSOR ------------------------------------------------------------------------------------ 7. Abstract We propose to observe comets at high spectral resolution in order to search for isotopic variants and in order to elucidate the emission mechanism of the various molecular species that are known. This knowledge of the emission mechanism is critical to interpreting observed fluxes from comets in terms of abundances which in turn provide our best clues to the conditions of temperature and pressure in the solar nebula. ------------------------------------------------------------------------------------ 8. Scientific Key Words: COMETS ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 4.75 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 2657c PI: P.i. Michael F. A'hearn Proposal Title: HIGH RESOLUTION SPECTROSCOPY OF COMETS ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Dr. Michael F. A'Hearn MARYLAND, UNIVERSITY OF USA Dr. Claude Arpigny LIEGE UNIVERSITY BELGIUM X Dr. Jean-Loup Bertaux CNRS, DEPARTMENT OF AERONOMY FRANCE X Dr. Paul D. Feldman JOHNS HOPKINS UNIVERSITY USA Dr. Sang J. Kim MARYLAND, UNIVERSITY OF USA Dr. Barry L. Lutz LOWELL OBSERVATORY USA Dr. David G. Schleicher LOWELL OBSERVATORY USA Dr. Harold A. Weaver STSCI USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. Because of uncertainties in the ephemerides of comets as well as uncertainties regarding HST's abilities to track moving targets, we propose to use WF/PC images (WF mode) to locate the photocenter of the comet on the first visit to the comet. Succeding visits can then be handled with the FOS internal acquisition function with a handover to HRS. A WFC image will be taken after each HRS exposure to confirm tracking. Exposure times assume a comet meeting but not exceding the TO criterion. a. Oxygen isotopes in OH: Large science aperture (spatial resolution not important, pointing not critical); echelle-B, order 20 centered near 2830, m*lambda = 56,600. Exposure = 45 min. b. Prompt emission of OH: Large science aperture for maximum sensitivity to weak lines from extended source. G270M centered at 3095A since resolution adequate. Centered on nucleus. Exposure time 10 minutes. This directly detects excited rotational states. Offset by 2 arcsec. Exposure time 15 minutes to measure change in lambda doublet population with distance from nucleus. Offset by 4 arcsec for same goal. Exposure time 20 minutes. Small science aperture centered on nucleus to determine inversion closest to nucleus. Exposure time 100 minutes. c . CS: Small science aperture; grating G270M centered at 2578. Large science aperture, echelle-B, order 22, centered at m*lambda = 56,700. Both exposures on photocenter sample, on average, very different distances from nucleus with maximum sensitivity and comparable (2.5x) resolution. SSA/G270M requires 100 min, LSA/ECH-B requires 40 min. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. This is a target of opportunity program to be activated upon the appearance of a suitable comet. Occasionally periodic comets meet the criterion for our TO. Comet P/Honda-Mrkos-Padjusakova meets the criterion for our TO during the nominal proposal period but will not be available in the 'actual' observing window. Once the actual observing window is known, periodic comets will be searched for a suitable target. Since ephemerides of comets are poorly known and since this proposal requires an accurate centering relative to the photocenter of the comet, WF/PC real time acquisition is needed for the first visit to the comet unless this program is executed immediately following one of the other cometary TO programs. Subsequent visits can be made without real-time acquisition using the FOS internal acquisition mode. Certain aspects of the program (prompt emission of OH) require scheduling at certain heliocentric radial velocities in order that the physically relevant processes can be detected. Page 3 ------------------------------------------------------------------------------------ 8. Additional comments or special requests. Criterion: Q(H2O) > 10**29 * r**2 * delta Our experience with IUE shows that targets of opportunity are frequent. We have averaged approximately 1.5 target of opportunity comets per year over 11 years of work with IUE. The criteria for this HST proposal are much more stringent since we do not propose to do work that can still be done with IUE. In 11 years with IUE, 7 comets satisfied this criterion so we expect a suitable target of opportunity once every year or two. The list of periodic comets will be searched when the actual observing window is known. ------------------------------------------------------------------------------------ 11. Address Information Name: MICHAEL F. A'HEARN Category: PI Institution: UNIVERSITY OF MARYLAND Address: ASTRONOMY PROGRAM BLDG. 224 RM. 1243 City: COLLEGE PARK State: MD Zip Code: 20742 Country: USA Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST c)Generic Targets ID = 2657c [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 7 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Selection Criteria |Acqui|FLX| Flux data No | Name | Description | |Prblm|REF| | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 COMET-TBD COMET TARGET OF THE WATER PRODUCTION RATE > EXT 1 SURF(V) = 12 +/- 1 OPPORTUNITY R=HELIOCENTRIC DISTANCE AND 2 SURF-LINE(3095) = 2.5 +/- 1.5 E-14 SOLAR ELONGATION > 50 DEGREES 3 W-LINE(3095) = 1.0 +/- 0.2 4 SURF-LINE(3085) = 1.3 +/- 0.3 E-12 5 W-LINE(3085) = 1.0 +/- 0.2 6 SURF-LINE(2830) = 1.3 +/- .3 E-15 7 W-LINE(2830) = 1.0 +/- 0.2 8 SURF-LINE(2578) = 2.0 +/- 0.5 E-13 9 W-LINE(2578) = 1.0 +/- 0.2 Comments: FLUX ESTIMATES FOR COMET BARELY MEETING TO CRITERION. FLUXES BASED ON PREVIOUS IUE MEASUREMENTS. THESE EMISSIONS ARE VARIABLE FROM COMET TO COMET AND WITH HELIO- CENTRIC AND GEOCENTRIC DISTANCES. ------------------------------------------------------------------------------------------------------------------------------------ 2 COMET-TBD- COMET TARGET OF ^ ^ 1 SURF(V) = 12 +/- 1 2ARCSEC OPPORTUNITY 2 SURF-LINE(3095) = 1.5 +/- 0.5 E-14 OFFSET FROM NUCLEUS 2 3 W-LINE(3095) = 1.0 +/- 0.2 ARCSEC TOWARD SUN 4 SURF-LINE(3085) = 1.3 +/- 0.3 E-12 5 W-LINE(3085) = 1.0 +/- 0.2 6 SURF-LINE(2830) = 1.3 +/- .3 E-15 7 W-LINE(2830) = 1.0 +/- 0.2 8 SURF-LINE(2578) = 0.5 +/- 0.2 E-13 9 W-LINE(2578) = 1.0 +/- 0.2 Comments: ^ ------------------------------------------------------------------------------------------------------------------------------------ 3 COMET-TBD- COMET TARGET OF ^ ^ 1 SURF(V) = 12 +/- 1 4ARCSEC OPPORTUNITY 2 SURF-LINE(3095) = 0.5 +/- 0.2 E-14 OFFSET FROM NUCLEUS 4 3 W-LINE(3095) = 1.0 +/- 0.2 ARC-SEC TO SUN 4 SURF-LINE(3085) = 1.3 +/- 0.3 E-12 5 W-LINE(3085) = 1.0 +/- 0.2 6 SURF-LINE(2830) = 1.3 +/- .3 E-15 7 W-LINE(2830) = 1.0 +/- 0.2 8 SURF-LINE(2578) = 0.2 +/- 0.05 E-13 9 W-LINE(2578) = 1.0 +/- 0.2 Comments: ^ ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2657c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 COMET-TBD WFC IMAGE ALL F791W 1 1S 1 1 INT ACQ FOR 2 SEQ 1-12 NO GAP TARG OF OPP / 1-12 Comments: THIS EXPOSURE OMITTED IF IMMEDIATELY PRECEDING EXPOSURE WAS FROM P2442 OR P2483 SEQ 1- 12 CAN BE INTERLEAVED WITH EXPOSURES FROM P2442 AND P2483 ------------------------------------------------------------------------------------------------------------------------------------ 2 ^ HRS ACCUM 2.0 G270M 3095 1 8M 10 2 2 SEQ 2-5 NON-INT 5M Comments: ADJUST TIME_PER_EXP FOR SEQ 2-5 TO FILL ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 3 COMET-TBD- HRS ACCUM 2.0 G270M 3095 1 10M 10 2 2 NON-INT / 2-5 2ARCSEC 8M Comments: OFFSET 2 ARCSEC FROM NUCLEUS TO SUN ------------------------------------------------------------------------------------------------------------------------------------ 4 COMET-TBD- HRS ACCUM 2.0 G270M 3095 1 15M 10 2 2 NON-INT / 2-5 4ARCSEC 12M Comments: OFFSET 4 ARCSEC FROM NUCLEUS TO SUN ------------------------------------------------------------------------------------------------------------------------------------ 5 ^ WFC IMAGE ALL F791W 1 1S 1 4 NON-INT / 2-5 Comments: MANEUVER UNDER GYROHOLD AFTER HRS EXPOSURE TO VERIFY POINTING ------------------------------------------------------------------------------------------------------------------------------------ 6 COMET-TBD HRS ACCUM 2.0 ECH-B 2830 1 35M 3 6 1 22M Comments: USE GYROHOLD TO FINISH EXPOSURE WHEN GUIDE STARS ARE LOST ------------------------------------------------------------------------------------------------------------------------------------ 7 ^ WFC IMAGE ALL F791W 1 1S 1 4 SEQ 6-7 NON-INT Comments: MANEUVER UNDER GYROHOLD AFTER HRS EXPOSURE TO VERIFY POINTING ------------------------------------------------------------------------------------------------------------------------------------ 8 ^ HRS ACCUM 2.0 G270M 2578 1 32M 10 8 3 20M Comments: USE GYROHOLD TO FINISH EXPOSURE WHEN GUIDE STARS ARE LOST ------------------------------------------------------------------------------------------------------------------------------------ 9 ^ WFC IMAGE ALL F791W 1 1S 1 4 SEQ 8-9 NON-INT Comments: MANEUVER UNDER GYROHOLD AFTER HRS EXPOSURE TO VERIFY POINTING ------------------------------------------------------------------------------------------------------------------------------------ 10 COMET-TBD FOS/RD ACQ/ 4.3 MIRROR MAP=BOTH 1 1.4S 3 ONBOARD ACQ FOR 11 FIRMWAR BRIGHT=480000 E FAINT=4800 ------------------------------------------------------------------------------------------------------------------------------------ 11 ^ HRS ACCUM 0.25 G270M 2578 1 50M 10 8 3 50M ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2657c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 12 ^ WFC IMAGE ALL F791W 1 1S 1 4 SEQ 11-12 NON-INT Comments: MANEUVER UNDER GYROHOLD AFTER HRS EXPOSURE TO VERIFY POINTING ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 2657c [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC HRS FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACCUM ACQ/FIRMWARE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters MAP=BOTH BRIGHT=480000 FAINT=4800 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 4.75 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category COMET ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements INT ACQ FOR 2; SEQ 1-12 NO GAP; TARG OF OPP / 1-12 SEQ 2-5 NON-INT NON-INT / 2-5 SEQ 6-7 NON-INT SEQ 8-9 NON-INT ONBOARD ACQ FOR 11 SEQ 11-12 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F791W G270M ECH-B MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names COMET-TBD COMET-TBD-2ARCSEC COMET-TBD-4ARCSEC ------------------------------------------------------------------------------------------------------------------------------------