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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
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2. Scientific Category 3. Proposal For 4. Cycle
SOLAR SYSTEM GO 6
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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
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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.
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Observations Description
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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
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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
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Additional Comments
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Data Distribution
Media: 8MM
Blocking Factor: 10
Ship To: PI_Address
Ship Via: UPS
Email: ,
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TARGET LIST b)Solar System Targets
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TARGET NUMBER: 1 | TARGET NAME: KOPFF
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TARGET DESCRIPTION: COMET 22P/KOPFF
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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 |
|
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TARGET POSITION LEVEL 3 | WINDOWS
|
| RANGE KOPFF EARTH LT 0.6
|
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DATA | COMMENTS
|
V = 7.0+/-0.5 | Requires ephemeris correction.
B-V = 0.65 |
|
Ephemeris Uncertainty: 50000 KM |
Acquisition Uncertainty: 10 " |
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TARGET NUMBER: 2 | TARGET NAME: HYAKUTAKE
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TARGET DESCRIPTION: COMET HYAKUTAKE
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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 |
|
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TARGET POSITION LEVEL 3 | WINDOWS
|
|
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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 " |
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Visit: 01
Visit Requirements: BETWEEN 18-JUN-96 AND 28-JUL-96 SEQ 1-3 WITHIN 24H GUID TOL 0.2"
On Hold Comments: <none>
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
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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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.
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12 KOPFF WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 40S REQ EPHEM CORR KOPFA
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13 KOPFF WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 180S REQ EPHEM CORR KOPFA
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14 KOPFF WFPC2 IMAGE PC1-FIX F439W CR-SPLIT = NO 2 400S REQ EPHEM CORR KOPFA
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Visit: 02
Visit Requirements: BETWEEN 18-JUN-96 AND 28-JUL-96 GUID TOL 0.2"
On Hold Comments: <none>
Additional Comments: Uplink required for ephemeris offset after visit 1. Use "use offset" for
all exposures this visit.
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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21 KOPFF FOS/RD ACQ 4.3 MIRROR 1 40S USE OFFSET KOPFF REQ EPHEM CORR KOPFA
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22 KOPFF FOS/RD ACCUM 4.3 G270H 1 24M USE OFFSET KOPFF REQ EPHEM CORR KOPFA
EXPAND NO SPLIT END ORBIT
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Visit: 03
Visit Requirements: BETWEEN 18-JUN-96 AND 28-JUL-96 GUID TOL 0.2"
On Hold Comments: <none>
Additional Comments: Uplink required for ephemeris offset after visit 1. Use "use offset" for
all exposures this visit.
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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31 KOPFF FOS/BL ACQ 4.3 MIRROR 1 200S USE OFFSET KOPFF REQ EPHEM CORR KOPFA
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32 KOPFF FOS/BL ACCUM 4.3 G190H 1 24M USE OFFSET KOPFF REQ EPHEM CORR KOPFA
EXPAND NO SPLIT END ORBIT
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33 KOPFF FOS/BL ACCUM 4.3 G190H 1 15M USE OFFSET KOPFF REQ EPHEM CORR KOPFA
EXPAND NO SPLIT
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34 KOPFF FOS/BL ACCUM 4.3 G190H 1 18M USE OFFSET KOPFF REQ EPHEM CORR KOPFA
EXPAND NO SPLIT END ORBIT
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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: <none>
Additional Comments: Visit should be completed in one orbit. Uplink offset correction to comet
ephemeris before Visit 5.
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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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.
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42 HYAKUTAKE WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 5S REQ EPHEM CORR HY1
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43 HYAKUTAKE WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 25S REQ EPHEM CORR HY1
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44 HYAKUTAKE WFPC2 IMAGE PC1-FIX F675W CR-SPLIT = NO 2 100S REQ EPHEM CORR HY1
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45 HYAKUTAKE WFPC2 IMAGE PC1-FIX F439W CR-SPLIT = NO 2 40S REQ EPHEM CORR HY1
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46 HYAKUTAKE WFPC2 IMAGE PC1-FIX F439W CR-SPLIT = NO 2 200S REQ EPHEM CORR HY1
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Visit: 05
Visit Requirements: BETWEEN 02-JUN-96 AND 09-JUN-96 SCHED 100% GUID TOL 0.2"
On Hold Comments: <none>
Additional Comments: Uplink required for ephemeris offset after visit 4. Use "use offset" for
all exposures this visit.
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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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
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52 HYAKUTAKE FOS/RD ACCUM 1.0 G270H 1 24M EXPAND NO SPLIT END ORBIT USE OFFSET HY2
REQ EPHEM CORR HY1
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Visit: 06
Visit Requirements: BETWEEN 02-JUN-96 AND 09-JUN-96 SCHED 100% GUID TOL 0.2"
On Hold Comments: <none>
Additional Comments: Uplink required for ephemeris offset after visit 4. Use "use offset" for
all exposures this visit.
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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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
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62 HYAKUTAKE FOS/BL ACCUM 1.0 G190H 1 24M EXPAND NO SPLIT END ORBIT USE OFFSET HY2
REQ EPHEM CORR HY1
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63 HYAKUTAKE FOS/BL ACCUM 1.0 G190H 1 15M EXPAND NO SPLIT USE OFFSET HY2 REQ EPHEM
CORR HY1
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64 HYAKUTAKE FOS/BL ACCUM 1.0 G190H 1 18M EXPAND NO SPLIT END ORBIT USE OFFSET HY2
REQ EPHEM CORR HY1
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Summary Form for Proposal 6591
Item Used in this proposal
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Configurations WFPC2 FOS/RD FOS/BL
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Opmodes IMAGE ACQ ACCUM
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Optional Parameters CR-SPLIT = NO SUB-STEP=4 COMB=YES
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Proposal Category GO
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Scientific Category SOLAR SYSTEM
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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
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Spectral Elements F675W F439W MIRROR G270H G190H
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Target Names KOPFF HYAKUTAKE
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