6591( 6) - 04/25/96 13:52 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6591 Version: 6 Check-in Date: 25-Apr-1996 13:42:27 1.Proposal Title: A Campaign to Determine the CO and \\cotwo\\ Abundances in Cometary Nuclei ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle SOLAR SYSTEM GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Paul D. Feldman The Johns Hopkins University CoI: Michael F. A'Hearn University of Maryland N CoI: Michel C. Festou Observatoire Midi-Pyr'e n'e es N CoI: Gian Paolo Tozzi Osservatorio Astrofisico di Arcetri N CoI: Harold A. Weaver Applied Research Corporation N ------------------------------------------------------------------------------------ 6. Abstract We propose a campaign to determine the abundances of CO and \cotwo , relative to H IIo , in a significant sample of comets, both targets of opportunity and periodic comets, over the next three years to address fundamental issues in the composition of cometary nuclei. In particular, we seek to reconcile an analysis based on recent HST\ and archival IUE\ data that suggest that the relative abundance of CO and the overall activity of a comet are correlated. The relative \cotwo\ abundance does not seem to be similarly correlated. To address the focussed objective, we require only 5 orbits per comet to obtain the required spectroscopic information. We anticipate that there may be two or three suitable candidates each year. ------------------------------------------------------------------------------------ 6591( 6) - 04/25/96 13:52 - [ 2] Observations Description ------------------------ To span a significant range of cometary activity, we desire to observe any comet available to observation with HST\\ with a production rate of \\qhtwoo\\ = 2 * 10^28 \\mols\\ or greater and within ~1 AU of the sun. Our experience with comets Hartley 2 and Shoemaker-Levy (not to be confused with Shoemaker- Levy 9) discussed above demonstrate that sufficient signal-to-noise is obtainable with one hour of integration time using the G190H grating of FOS to achieve detection of or significant upper limits to the CO and \\cotwo\\ column abundances in the comae of such comets. One other comet was observed by HST , 24P/Schaumasse, in March 1993 when it was at a heliocentric distance of 1.2 AU. The derived H IIo\\ production rate of this comet was 1.5 * 10^28 \\mols , and an upper limit of 5 Rayleighs emission in the strongest Cameron bands was obtained with 44 minutes of exposure. This serves as a good constraint for future observations. The PI and co- Is have been involved in the observation of over 50 comets, both targets-of-opportunity and periodic comets (some at more than one apparition), by IUE\\ over the past 15 years. IUE\\ is subject to similar solar avoidance constraints as HST , and the threshold for detectability (of longer wavelength features such as CS, \\cotwop , and OH) with the IUE\\ spectrographs was similarly of the order of 1 * 10^28 \\mols , so that we may expect 2 or 3 comets suitable for observation each year. Our orbit request is based on two targets, each requiring 5 orbits. We also indicate that a similar number of orbits will be required in each of cycles 7 and 8, but this number is subject to change when the STIS instrument sensitivity is properly taken into account. One of our requested targets is the periodic comet 22P/Kopff, which will reach perihelion of 1.58 AU in early July 1996. The water production rate of this comet near perihelion, determined from IUE\\ observations made in 1983, is ~ 5 * 10^28 \\mols\\ (Feldman and Festou 1992). However, since the brightness of the ultraviolet emissions of interest varies as r^-2Delta^-1, where r and Delta are the heliocentric and geocentric distances, respectively, and the viewing geometry in July 1996 will be ideal with Delta = 0.57 AU, our selection criterion is easily satisfied. For each comet to be observed we require five contiguous orbits to obtain the spectra needed to reliably determine the production rates of CO, \\cotwo , and H IIo , with minimal effect of cometary variability, if there is any. The first orbit will be a WFPC2 image with the comet located on the PC chip through a wide band red filter (F675W), in order to update the cometary ephemeris on the spacecraft. The last four orbits will utilize the FOS blue side with the 4.\\.''3 aperture to maximize the throughput from an extended source. While the red digicon has roughly twice the sensitivity than the blue digicon in the critical region of the G190H grating, the lower dark background and susceptibility to long-wavelength grating scattered light make the blue side preferable. The second orbit will use the FOS with G270H to obtain the OH brightness needed to determine \\qhtwoo . An acquisition image will be taken to verify the pointing and any correction, if necessary, will be made if an uplink to the spacecraft is available. The G270H spectrum will also provide a measure of the dust scattered sunlight and the \\cotwop\\ emission at 2890 Angstrom . The latter may be useful in tying these observations to the IUE\\ comet database, although Feldman Etal\\ (1996) demonstrate that the \\cotwo\\ and \\cotwop\\ abundances in the field of view are not trivially related. The remaining three orbits will be used to acquire approximately one hour of integration time with G190H, to address our objectives of determining the abundances of CO, \\cotwo , and C in the coma. Real Time Justification ----------------------- As noted above, some of the comets to be observed may be targets of opportunity and need to be scheduled on relatively short notice following the discovery. Since the ephemerides of such comets is often not well known (uncertainties of a few arc-seconds are not uncommon), it is necessary to use an interactive acquisition and the ability to uplink the position changes before any of the spectroscopic measurements are made. Comet 22P/Kopff reaches perihelion on 2 July 1996 and remains near minimum geocentric distance for the following three weeks. The observations of this comet must be scheduled during this period. Ground-based monitoring of the activity of any of the comets to be observed will be provided by co-I A'Hearn and his collaborators at Lowell Observatory and at Perth, Australia. Co-I Festou will coordinate our program with European millimeter-wave astronomers at SEST or IRAM. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6591( 6) - 04/25/96 13:52 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6591( 6) - 04/25/96 13:52 - [ 4] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: KOPFF ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: COMET 22P/KOPFF ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | TYPE=COMET,Q=1.5795617,E=0.5440739,I=4.7 | 2143,O=120.91329,W=162.83487,T = 02-Jul- | 1996:04:47:42.0,EQUINOX=J2000,EPOCH=16- | Jul-1996 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | RANGE KOPFF EARTH LT 0.6 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 7.0+/-0.5 | Requires ephemeris correction. B-V = 0.65 | | Ephemeris Uncertainty: 50000 KM | Acquisition Uncertainty: 10 " | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: HYAKUTAKE ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: COMET HYAKUTAKE ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | TYPE=COMET,Q=0.230200536,E=0.999887068,I | =124.9229369,O=188.0453468,W=130.1786541 | ,T = 01-May- | 1996:09:26:55.0,EQUINOX=J2000,EPOCH=03- | May-1996 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 13 | V-mag is for 0.7 arcsec diameter B-V = 0.8 | aperture. Elements are from Yeomans V-R = 0.4 | ref solution 34 and must be updated | prior to final scheduling. | Ephemeris Uncertainty: 50000 KM | Acquisition Uncertainty: 30 " | ------------------------------------------------------------------------------------------------------------------------------------ 6591( 6) - 04/25/96 13:52 - [ 5] Visit: 01 Visit Requirements: BETWEEN 18-JUN-96 AND 28-JUL-96 SEQ 1-3 WITHIN 24H GUID TOL 0.2" On Hold Comments: Additional Comments: Visit should be completed in one orbit. Uplink offset correction to comet ephemeris before Visit 2. RANGE and BETWEEN requirements define same window. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 KOPFF WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 10S SAVE OFFSET KOPFF REQ EPHEM CORR KOPFA Comments: Determines ephemeris correction for visits 2- 3. ------------------------------------------------------------------------------------------------------------------------------------ 12 KOPFF WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 40S REQ EPHEM CORR KOPFA ------------------------------------------------------------------------------------------------------------------------------------ 13 KOPFF WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 180S REQ EPHEM CORR KOPFA ------------------------------------------------------------------------------------------------------------------------------------ 14 KOPFF WFPC2 IMAGE PC1-FIX F439W CR-SPLIT = NO 2 400S REQ EPHEM CORR KOPFA ------------------------------------------------------------------------------------------------------------------------------------ 6591( 6) - 04/25/96 13:52 - [ 6] Visit: 02 Visit Requirements: BETWEEN 18-JUN-96 AND 28-JUL-96 GUID TOL 0.2" On Hold Comments: Additional Comments: Uplink required for ephemeris offset after visit 1. Use "use offset" for all exposures this visit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 21 KOPFF FOS/RD ACQ 4.3 MIRROR 1 40S USE OFFSET KOPFF REQ EPHEM CORR KOPFA ------------------------------------------------------------------------------------------------------------------------------------ 22 KOPFF FOS/RD ACCUM 4.3 G270H 1 24M USE OFFSET KOPFF REQ EPHEM CORR KOPFA EXPAND NO SPLIT END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 6591( 6) - 04/25/96 13:52 - [ 7] Visit: 03 Visit Requirements: BETWEEN 18-JUN-96 AND 28-JUL-96 GUID TOL 0.2" On Hold Comments: Additional Comments: Uplink required for ephemeris offset after visit 1. Use "use offset" for all exposures this visit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 31 KOPFF FOS/BL ACQ 4.3 MIRROR 1 200S USE OFFSET KOPFF REQ EPHEM CORR KOPFA ------------------------------------------------------------------------------------------------------------------------------------ 32 KOPFF FOS/BL ACCUM 4.3 G190H 1 24M USE OFFSET KOPFF REQ EPHEM CORR KOPFA EXPAND NO SPLIT END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 33 KOPFF FOS/BL ACCUM 4.3 G190H 1 15M USE OFFSET KOPFF REQ EPHEM CORR KOPFA EXPAND NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 34 KOPFF FOS/BL ACCUM 4.3 G190H 1 18M USE OFFSET KOPFF REQ EPHEM CORR KOPFA EXPAND NO SPLIT END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 6591( 6) - 04/25/96 13:52 - [ 8] Visit: 04 Visit Requirements: BETWEEN 02-JUN-96 AND 09-JUN-96 SEQ 4-6 WITHIN 24H SCHED 100% GUID TOL 0.2" On Hold Comments: Additional Comments: Visit should be completed in one orbit. Uplink offset correction to comet ephemeris before Visit 5. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 41 HYAKUTAKE WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 1S SAVE OFFSET HY2 REQ EPHEM CORR HY1 Comments: Determines ephemeris correction for visits 5- 6. ------------------------------------------------------------------------------------------------------------------------------------ 42 HYAKUTAKE WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 5S REQ EPHEM CORR HY1 ------------------------------------------------------------------------------------------------------------------------------------ 43 HYAKUTAKE WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 25S REQ EPHEM CORR HY1 ------------------------------------------------------------------------------------------------------------------------------------ 44 HYAKUTAKE WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 100S REQ EPHEM CORR HY1 ------------------------------------------------------------------------------------------------------------------------------------ 45 HYAKUTAKE WFPC2 IMAGE PC1-FIX F439W CR-SPLIT = NO 2 40S REQ EPHEM CORR HY1 ------------------------------------------------------------------------------------------------------------------------------------ 46 HYAKUTAKE WFPC2 IMAGE PC1-FIX F439W CR-SPLIT = NO 2 200S REQ EPHEM CORR HY1 ------------------------------------------------------------------------------------------------------------------------------------ 6591( 6) - 04/25/96 13:52 - [ 9] Visit: 05 Visit Requirements: BETWEEN 02-JUN-96 AND 09-JUN-96 SCHED 100% GUID TOL 0.2" On Hold Comments: Additional Comments: Uplink required for ephemeris offset after visit 4. Use "use offset" for all exposures this visit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 51 HYAKUTAKE FOS/RD IMAGE 4.3 G270H Y-SIZE=5,Y- 1 300S USE OFFSET HY2 REQ EPHEM CORR HY1 SEQ 51-52 SPACE=128,COMB= NON-INT YES,SUB-STEP=4 ------------------------------------------------------------------------------------------------------------------------------------ 52 HYAKUTAKE FOS/RD ACCUM 1.0 G270H 1 24M EXPAND NO SPLIT END ORBIT USE OFFSET HY2 REQ EPHEM CORR HY1 ------------------------------------------------------------------------------------------------------------------------------------ 6591( 6) - 04/25/96 13:52 - [ 10] Visit: 06 Visit Requirements: BETWEEN 02-JUN-96 AND 09-JUN-96 SCHED 100% GUID TOL 0.2" On Hold Comments: Additional Comments: Uplink required for ephemeris offset after visit 4. Use "use offset" for all exposures this visit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 61 HYAKUTAKE FOS/BL IMAGE 4.3 G270H Y-SIZE=5,Y- 1 300S USE OFFSET HY2 REQ EPHEM CORR HY1 SEQ 61-62 SPACE=128,COMB= NON-INT YES,SUB-STEP=4 ------------------------------------------------------------------------------------------------------------------------------------ 62 HYAKUTAKE FOS/BL ACCUM 1.0 G190H 1 24M EXPAND NO SPLIT END ORBIT USE OFFSET HY2 REQ EPHEM CORR HY1 ------------------------------------------------------------------------------------------------------------------------------------ 63 HYAKUTAKE FOS/BL ACCUM 1.0 G190H 1 15M EXPAND NO SPLIT USE OFFSET HY2 REQ EPHEM CORR HY1 ------------------------------------------------------------------------------------------------------------------------------------ 64 HYAKUTAKE FOS/BL ACCUM 1.0 G190H 1 18M EXPAND NO SPLIT END ORBIT USE OFFSET HY2 REQ EPHEM CORR HY1 ------------------------------------------------------------------------------------------------------------------------------------ 6591( 6) - 04/25/96 13:52 - [ 11] Summary Form for Proposal 6591 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 FOS/RD FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT = NO SUB-STEP=4 COMB=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 18-JUN-96 AND 28-JUL-96 SEQ 1-3 WITHIN 24H GUID TOL 0.2" SAVE OFFSET KOPFF REQ EPHEM CORR KOPFA BETWEEN 18-JUN-96 AND 28-JUL-96 GUID TOL 0.2" USE OFFSET KOPFF REQ EPHEM CORR KOPFA USE OFFSET KOPFF REQ EPHEM CORR KOPFA EXPAND NO SPLIT END ORBIT USE OFFSET KOPFF REQ EPHEM CORR KOPFA EXPAND NO SPLIT BETWEEN 02-JUN-96 AND 09-JUN-96 SEQ 4-6 WITHIN 24H SCHED 100% GUID TOL 0.2" SAVE OFFSET HY2 REQ EPHEM CORR HY1 BETWEEN 02-JUN-96 AND 09-JUN-96 SCHED 100% GUID TOL 0.2" USE OFFSET HY2 REQ EPHEM CORR HY1 SEQ 51-52 NON-INT EXPAND NO SPLIT END ORBIT USE OFFSET HY2 REQ EPHEM CORR HY1 USE OFFSET HY2 REQ EPHEM CORR HY1 SEQ 61-62 NON-INT EXPAND NO SPLIT USE OFFSET HY2 REQ EPHEM CORR HY1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F675W F439W MIRROR G270H G190H ------------------------------------------------------------------------------------------------------------------------------------ Target Names KOPFF HYAKUTAKE ------------------------------------------------------------------------------------------------------------------------------------