7312( 7) - 11/17/97 15:18 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7312 Version: 7 Check-in Date: 17-Nov-1997 15:16:17 1.Proposal Title: Investigating Volatile Depletion in Two Periodic Comets: 2P/Encke and 103P/Hartley 2 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: HAROLD WEAVER THE JOHNS HOPKINS UNIVERSITY CoI: Michael A'Hearn University of Maryland, College Park N CoI: Claude Arpigny Universite de Liege N CoI: Paul Feldman Johns Hopkins University N ------------------------------------------------------------------------------------ 5. Abstract Current theories predict that the near-surface regions of cometary nuclei should become increasingly devolatilized during successive passages through the inner solar system. We propose to investigate this hypothesis by performing ``deep'' searches for three important cometary volatiles, CO, CO2, and S2 in comet 2P/Encke, which has the shortest period and one of the smallest perihelion distances of any known comet. Encke makes a particularly close approach to the Earth in July 1997 mbox(Delta_min~0.2 AU), and this significantly enhances the sensitivity limits that can be achieved on this intrinsically faint object. We expect to probe CO and CO2 to abundance levels of <=2% relative to H2O. S2 should be detectable if its abundance in Encke is comparable to that observed in comets mboxIRAS- Araki-Alcock and Hyakutake. We also propose to observe comet 103P/Hartley 2, which is the brightest short period comet accessible to HST in Cycle 7. The principal scientific objective in this case is to establish definitively that the CO abundance is significantly depleted in Hartley 2, as was indicated by previous HST observations in 1991. The above program is uniquely suited to the capabilities of HST and cannot be accomplished with the same sensitivity from any other observatory. ------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 2] Observations Description ------------------------ This program contains two targets: comet 2P/Encke and comet 103P/Hartley 2. 4 orbits are devoted to Encke and 4 orbits are devoted to Hartley 2. ENCKE: The WINDOW for these observations is only 8 days long: from 29-JUNE-1997 to 07-JUL- 1997, inclusive. The former date is the first day that the comet exits the SEZ following its perihelion. The comet's brightness is a strong function of heliocentric distance, which is why we need to observe as close to perihelion as possible. Each orbit is a different visit, so there are 4 visits total. If possible, the orbits should be scheduled consecutively. Only CCD observations are performed (i.e., there are no MAMA observations). Each of the 4 visits contains an identical set of operations consisting of the following: GS ACQ ONBOARD ACQ using STIS/CCD (texp=0.1 sec) STIS/CCD ACCUM using G230LB with CR- SPLIT=4 and 52X0.5 aperture STIS/CCD ACCUM with MIRROR (texp=1 sec) STIS/CCD ACCUM with MIRROR (texp=5 sec) The CCD images are used for both target acquisition and imaging. The images use different exp times to ensure that we have at least one that does not saturate the peak pixel. At the time of these observations, 1 CCD pixel projects to 7.25 km at the comet. Since the comet nucleus is thought to be about 5 km in diameter, we will be very close to resolving the nucleus. The geocentric distance of the comet will be 0.2 AU and the apparent motion will be 0.2"/sec. Thus, we expect that these observations will be executed under GYRO control. This is another reason why we are spending a fair amount of time on imaging; the images will allow us to figure out where we were pointed. Although the observations will be executed under GYRO control, it is very important that a GS ACQ be executed at the start of each orbit to get the comet within the 5" x 5" FOV of the CCD TA subarray. HARTLEY 2: This comet has a very long observing WINDOW: anytime between 01-DEC-1997 and 20-JAN- 1998 is OK. Thus, the time having the least SAA impact and the best GS coverage should be selected. Each orbit is a different visit, so there are 4 visits total. If possible, all 4 orbits should be scheduled consecutively. Target acquisition is done with the CCD and all spectroscopy is done with the MAMAs. The apparent motion of the comet is 0.05"/sec, which means that most, if not all, of a single orbit can be supported by a single pair of GSs. However, different orbits will almost certainly require different GSs, which is why we are calling out the 4 orbits as 4 different visits. If GS HANDOFF allows for a more efficient program, then we would be willing to try that. Two of the visits contain identical operations and are referred to as the NUV group and the remaining two visits are also identical to each other and are referred to as the EUV group. Their activities are: NUV orbit (there are 2 orbits of these): GS ACQ ONBOARD ACQ using STIS/CCD (texp=10 sec) STIS/NUV-MAMA ACCUM using G230L with the 52X0.5 aperture STIS/CCD ACCUM with MIRROR (texp=30 sec) EUV orbit (there are 2 orbits of these): GS ACQ ONBOARD ACQ using STIS/CCD (texp=10 sec) STIS/EUV-MAMA ACCUM using G140L with the 52x2 aperture STIS/CCD ACCUM with MIRROR (texp=30 sec) Real Time Justification ----------------------- For maximum sensitivity, the Encke observations should be done sometime during the first two weeks in July 1997, which makes them TIME-CRITICAL. We will probably attempt to make coordinated infrared observations, but that will not drive the scheduling of the HST observations. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 3] Data Distribution Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 4] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: ENCKE ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: COMET Encke ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | TYPE=COMET,Q=0.331395403,E=0.85001298,I= | 11.929611,O=334.721716,W=186.271735,T = | 23-May- | 1997:14:18:19.2,EQUINOX=J2000,EPOCH=01- | Jun-1997 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 15+/-2 | V-mag is for the nucleus. The coma B-V = 0.8 | will contribute very little flux to V-R = 0.4 | the peak pixel. These elements are | from JPL27 and might need an update | prior to final scheduling. | Ephemeris Uncertainty: 725 KM | Acquisition Uncertainty: 5 " | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: HARTLEY2 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: COMET Hartley2 ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | TYPE=COMET,Q=1.0317265,E=0.7003833,I=13. | 61904,O=219.95470,W=180.72319,T = 22-Dec | -1997:00:31:56.4,EQUINOX=J2000,EPOCH=18- | Dec-1997,A1=-1.59609227109E- | 09,A2=4.2861807789E-10 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 15+/-2 | V-mag is for the nucleus. The coma B-V = 0.8 | will contribute very little flux to V-R = 0.4 | the peak pixel. These elements are | from JPL5 and will need an update | prior to final scheduling. | Ephemeris Uncertainty: 2900 KM | Acquisition Uncertainty: 5 " | 7312( 7) - 11/17/97 15:18 - [ 5] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 6] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 29-JUN-97 AND 7-JUL-97 SEQ 1-4 WITHIN 10H SCHED 100% DROP TO GYRO IF NECESSARY On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 ENCKE STIS/C ACQ F28X50L MIRROR 1 0.1 S REQ EPHEM CORR ENCKE1 CD P ONBOARD ACQ FOR 12-14 SEQ 11-14 NON-INT Comments: TA sequence ------------------------------------------------------------------------------------------------------------------------------------ 12 ENCKE STIS/C ACCUM 52X0.5 G230LB 2375 CR-SPLIT=4 1 24 M REQ EPHEM CORR ENCKE1 CD EXPAND Comments: Spectroscopic exposures. ------------------------------------------------------------------------------------------------------------------------------------ 13 ENCKE STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 1 S REQ EPHEM CORR ENCKE1 MAX CD P DUR 100% Comments: First image at end to check pointing. ------------------------------------------------------------------------------------------------------------------------------------ 14 ENCKE STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 5 S REQ EPHEM CORR ENCKE1 MAX CD P DUR 100% END ORBIT Comments: Second image at end to check pointing. ------------------------------------------------------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 7] Visit: 02 Visit Priority: Visit Requirements: SCHED 100% DROP TO GYRO IF NECESSARY On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 21 ENCKE STIS/C ACQ F28X50L MIRROR 1 0.1 S REQ EPHEM CORR ENCKE1 CD P ONBOARD ACQ FOR 22-24 SEQ 21-24 NON-INT Comments: TA sequence ------------------------------------------------------------------------------------------------------------------------------------ 22 ENCKE STIS/C ACCUM 52X0.5 G230LB 2375 CR-SPLIT=4 1 24 M REQ EPHEM CORR ENCKE1 CD EXPAND Comments: Spectroscopic exposures. ------------------------------------------------------------------------------------------------------------------------------------ 23 ENCKE STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 1 S REQ EPHEM CORR ENCKE1 MAX CD P DUR 100% Comments: First image at end to check pointing. ------------------------------------------------------------------------------------------------------------------------------------ 24 ENCKE STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 5 S REQ EPHEM CORR ENCKE1 MAX CD P DUR 100% END ORBIT Comments: Second image at end to check pointing. ------------------------------------------------------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 8] Visit: 03 Visit Priority: Visit Requirements: SCHED 100% DROP TO GYRO IF NECESSARY On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 31 ENCKE STIS/C ACQ F28X50L MIRROR 1 0.1 S REQ EPHEM CORR ENCKE1 CD P ONBOARD ACQ FOR 32-34 SEQ 31-34 NON-INT Comments: TA sequence ------------------------------------------------------------------------------------------------------------------------------------ 32 ENCKE STIS/C ACCUM 52X0.5 G230LB 2375 CR-SPLIT=4 1 24 M REQ EPHEM CORR ENCKE1 CD EXPAND Comments: Spectroscopic exposures. ------------------------------------------------------------------------------------------------------------------------------------ 33 ENCKE STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 1 S REQ EPHEM CORR ENCKE1 MAX CD P DUR 100% Comments: First image at end to check pointing. ------------------------------------------------------------------------------------------------------------------------------------ 34 ENCKE STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 5 S REQ EPHEM CORR ENCKE1 MAX CD P DUR 100% END ORBIT Comments: Second image at end to check pointing. ------------------------------------------------------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 9] Visit: 04 Visit Priority: Visit Requirements: SCHED 100% DROP TO GYRO IF NECESSARY On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 41 ENCKE STIS/C ACQ F28X50L MIRROR 1 0.1 S REQ EPHEM CORR ENCKE1 CD P ONBOARD ACQ FOR 42-44 SEQ 41-44 NON-INT Comments: TA sequence ------------------------------------------------------------------------------------------------------------------------------------ 42 ENCKE STIS/C ACCUM 52X0.5 G230LB 2375 CR-SPLIT=4 1 24 M REQ EPHEM CORR ENCKE1 CD EXPAND Comments: Spectroscopic exposures. ------------------------------------------------------------------------------------------------------------------------------------ 43 ENCKE STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 1 S REQ EPHEM CORR ENCKE1 MAX CD P DUR 100% Comments: First image at end to check pointing. ------------------------------------------------------------------------------------------------------------------------------------ 44 ENCKE STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 5 S REQ EPHEM CORR ENCKE1 MAX CD P DUR 100% END ORBIT Comments: Second image at end to check pointing. ------------------------------------------------------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 10] Visit: 05 Visit Priority: Visit Requirements: BETWEEN 01-DEC-97 AND 20-JAN-98 SEQ 5-8 WITHIN 10H SCHED 100% On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 51 HARTLEY2 STIS/C ACQ F28X50L MIRROR 1 10 S REQ EPHEM CORR HART1 CD P ONBOARD ACQ FOR 52-53 SEQ 51-53 NON-INT Comments: TA sequence ------------------------------------------------------------------------------------------------------------------------------------ 52 HARTLEY2 STIS/N ACCUM 52X0.5 G230L 2376 2 12 M REQ EPHEM CORR HART1 UV-MAM EXPAND A Comments: Spectroscopic exposures. ------------------------------------------------------------------------------------------------------------------------------------ 53 HARTLEY2 STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 30 S REQ EPHEM CORR HART1 MAX CD P DUR 100% END ORBIT Comments: Verification image. ------------------------------------------------------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 11] Visit: 06 Visit Priority: Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 61 HARTLEY2 STIS/C ACQ F28X50L MIRROR 1 10 S REQ EPHEM CORR HART2 CD P ONBOARD ACQ FOR 62-63 SEQ 61-63 NON-INT Comments: TA sequence ------------------------------------------------------------------------------------------------------------------------------------ 62 HARTLEY2 STIS/N ACCUM 52X0.5 G230L 2376 2 12 M REQ EPHEM CORR HART2 UV-MAM EXPAND A Comments: Spectroscopic exposures. ------------------------------------------------------------------------------------------------------------------------------------ 63 HARTLEY2 STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 30 S REQ EPHEM CORR HART2 MAX CD P DUR 100% END ORBIT Comments: Verification image. ------------------------------------------------------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 12] Visit: 07 Visit Priority: Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 71 HARTLEY2 STIS/C ACQ F28X50L MIRROR 1 10 S REQ EPHEM CORR HART3 CD P ONBOARD ACQ FOR 72-73 SEQ 71-73 NON-INT Comments: TA sequence ------------------------------------------------------------------------------------------------------------------------------------ 72 HARTLEY2 STIS/F ACCUM 52X2 G140L 1425 2 12 M REQ EPHEM CORR HART3 UV-MAM EXPAND A Comments: Spectroscopic exposures. ------------------------------------------------------------------------------------------------------------------------------------ 73 HARTLEY2 STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 30 S REQ EPHEM CORR HART3 MAX CD P DUR 100% END ORBIT Comments: Verification image. ------------------------------------------------------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 13] Visit: 08 Visit Priority: Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 81 HARTLEY2 STIS/C ACQ F28X50L MIRROR 1 10 S REQ EPHEM CORR HART4 CD P ONBOARD ACQ FOR 82-83 SEQ 81-83 NON-INT Comments: TA sequence ------------------------------------------------------------------------------------------------------------------------------------ 82 HARTLEY2 STIS/F ACCUM 52X2 G140L 1425 2 12 M REQ EPHEM CORR HART4 UV-MAM EXPAND A Comments: Spectroscopic exposures. ------------------------------------------------------------------------------------------------------------------------------------ 83 HARTLEY2 STIS/C ACCUM F28X50L MIRROR CR-SPLIT=NO,GAIN=4 1 30 S REQ EPHEM CORR HART4 MAX CD P DUR 100% END ORBIT Comments: Verification image. ------------------------------------------------------------------------------------------------------------------------------------ 7312( 7) - 11/17/97 15:18 - [ 14] Summary Form for Proposal 7312 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=4 GAIN=4 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 29-JUN-97 AND 7-JUL-97 SEQ 1-4 WITHIN 10H SCHED 100% DROP TO GYRO IF NECESSARY REQ EPHEM CORR ENCKE1 ONBOARD ACQ FOR 12-14 SEQ 11-14 NON-INT REQ EPHEM CORR ENCKE1 EXPAND REQ EPHEM CORR ENCKE1 MAX DUR 100% REQ EPHEM CORR ENCKE1 MAX DUR 100% END ORBIT REQ EPHEM CORR ENCKE1 ONBOARD ACQ FOR 22-24 SEQ 21-24 NON-INT REQ EPHEM CORR ENCKE1 ONBOARD ACQ FOR 32-34 SEQ 31-34 NON-INT REQ EPHEM CORR ENCKE1 ONBOARD ACQ FOR 42-44 SEQ 41-44 NON-INT BETWEEN 01-DEC-97 AND 20-JAN-98 SEQ 5-8 WITHIN 10H SCHED 100% REQ EPHEM CORR HART1 ONBOARD ACQ FOR 52-53 SEQ 51-53 NON-INT REQ EPHEM CORR HART1 EXPAND REQ EPHEM CORR HART1 MAX DUR 100% END ORBIT REQ EPHEM CORR HART2 ONBOARD ACQ FOR 62-63 SEQ 61-63 NON-INT REQ EPHEM CORR HART2 EXPAND REQ EPHEM CORR HART2 MAX DUR 100% END ORBIT REQ EPHEM CORR HART3 ONBOARD ACQ FOR 72-73 SEQ 71-73 NON-INT REQ EPHEM CORR HART3 EXPAND REQ EPHEM CORR HART3 MAX DUR 100% END ORBIT REQ EPHEM CORR HART4 ONBOARD ACQ FOR 82-83 SEQ 81-83 NON-INT REQ EPHEM CORR HART4 EXPAND REQ EPHEM CORR HART4 MAX DUR 100% END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G230LB G230L G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names ENCKE HARTLEY2 ------------------------------------------------------------------------------------------------------------------------------------