7494( 6) - 03/12/98 15:38 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7494 Version: 6 Check-in Date: 12-Mar-1998 15:36:17 1.Proposal Title: The mass ratio of Charon to Pluto ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: CATHERINE OLKIN LOWELL OBSERVATORY CoI: Otto Franz Lowell Observatory N CoI: Larry Wasserman Lowell Observatory N ------------------------------------------------------------------------------------ 5. Abstract We propose to determine the mass ratio of Charon to Pluto from astrometric measurements of Pluto, its satellite and at least two reference stars with the Fine Guidance Sensors. The mass ratio is a basic parameter describing the binary system and is critical to determine the individual densities of Pluto and Charon. The density is diagnostic of the interiors of Pluto and Charon and the origin of the binary system. There have been previous attempts both from the ground and HST (with WFPC) to determine this ratio and only two of the solutions agree within their errors. The ground-based observations are complicated by the overlap of Pluto and Charon images due to their small separation. The previous HST observations (before the servicing mission) had significant field distortions to remove and PSF overlap between Pluto and Charon. The FGS has been calibrated to understand systematic effects in astrometric observations and has demonstrated its capabilities by determining the orbits of faint nearby M-dwarf binary systems with similar separations and magnitude differences. The proposed observations would use a proven method to provide a precise estimate of the mass ratio of Charon to Pluto. This should settle the debate over the value of the Pluto-Charon mass ratio that began when the previous determinations disagreed. ------------------------------------------------------------------------------------ 7494( 6) - 03/12/98 15:38 - [ 2] Observations Description ------------------------ For five orbits, we will have the following sequence of observations (i) the Pluto-Charon system in POS mode (ii) Pluto-Charon in TRANS mode, (iii) four (or five) reference stars in the same pickle as Pluto-Charon observed in POS mode, (iv) revisit the first reference star in POS mode. Orbit 1 will observe four reference stars (fixed target numbers: 10, 6, 7, and 9). Orbit 2 will observe five reference stars (fixed target numbers: 10, 6, 7, 8, and 9). Orbits three, four and five will observe the same four reference stars (fixed target numbers: 6, 7, 8, and 9). With this plan for reference stars, we are maximizing the number of reference stars common to all orbits. For each orbit, we have given a reference position for the Pluto-Charon system as a fixed target because Pluto does not move enough to be considered a moving target during the requested window of observation. We will use FGS3 and filter F583W since they have been extensively calibrated for precise astrometry. Real Time Justification ----------------------- We do not require real-time observations, but we do have some special scheduling requirements. We require that the observations occur when Pluto, Charon and at least four field stars are observable in the field of view of FGS3 over a five day period. This requirement limits the window of opportunity to times when Pluto is near its stationary point. During cycle 7, this occurs in August 1997 and March 1998. The August 1997 opportunity does not have a favorable distribution of reference stars; therefore, we request observations in March 1998 when we can observe Pluto and four (or five) field stars over a five day period. The time constraints on each visit ensure good orbital phase coverage of the Pluto-Charon system and that Pluto and Charon are in a favorable orientation for scanning. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Otto Franz*Lowell Observatory*1400 W. Mars Hill Rd.*Flagstaff, AZ 86001 Ship Via: Email: ogf@lowell.edu ------------------------------------------------------------------------------------ 7494( 6) - 03/12/98 15:38 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PLUTO-1 STAR RA = 16H 33M 9.891S +/- 0.5", J2000 V = 13.00+/-0.05 DEC =-9D 35' 14.20" +/- 0.5" Comments: Pluto at 12h 3/12/98 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 0.0 0.0 0.0 0.0 2 PLUTO-2 STAR RA = 16H 33M 9.890S +/- 0.5", J2000 V = 13.00+/-0.05 DEC =-9D 35' 4.36" +/- 0.5" Comments: Pluto at 12h 3/13/98 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 0.0 0.0 0.0 0.0 3 PLUTO-3 STAR RA = 16H 33M 9.380S +/- 0.5", J2000 V = 13.00+/-0.05 DEC =-9D 34' 14.33" +/- 0.5" Comments: Pluto at 12h 3/14/98 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 0.0 0.0 0.0 0.0 4 PLUTO-4 STAR RA = 16H 33M 9.121S +/- 0.5", J2000 V = 13.00+/-0.05 DEC =-9D 34' 1.63" +/- 0.5" Comments: Pluto at 12h 3/15/98 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 0.0 0.0 0.0 0.0 5 PLUTO-5 STAR RA = 16H 33M 8.810S +/- 0.5", J2000 V = 13.00+/-0.05 DEC =-9D 33' 48.85" +/- 0.5" Comments: Pluto at 12h 3/16/98 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 0.0 0.0 0.0 0.0 6 PLUTO-1-REF CALIBRATION,ASTROMETRIC RA = 248.27998D +/- 0.00014D, J2000 V = 15.35+/-0.2 DEC = -9.58348D +/- 0.00014D Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 0.0 0.0 0.0 0.0 7 PLUTO-2-REF CALIBRATION,ASTROMETRIC RA = 248.19700D +/- 0.00014D, J2000 V = 12.76+/-0.2 DEC = -9.58104D +/- 0.00014D Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 0.0 0.0 0.0 0.0 8 PLUTO-3-REF CALIBRATION,ASTROMETRIC RA = 248.27513D +/- 0.00014D, J2000 V = 14.28+/-0.2 DEC = -9.55919D +/- 0.00014D Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 0.0 0.0 0.0 0.0 9 PLUTO-4-REF CALIBRATION,ASTROMETRIC RA = 248.33270D +/- 0.00014D, J2000 V = 14.69+/-0.2 DEC = -9.57326D +/- 0.00014D Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 0.0 0.0 0.0 0.0 10 PLUTO-5-REF CALIBRATION,ASTROMETRIC RA = 248.37731D +/- 0.00014D, J2000 V = 14.92+/-0.2 DEC = -9.63179D +/- 0.00014D 7494( 6) - 03/12/98 15:38 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 0.0 0.0 0.0 0.0 7494( 6) - 03/12/98 15:38 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PCS MODE Fine ORIENTation 274D TO 276D BETWEEN 12-MAR-98:4:00:00 AND 12-MAR -98:8:00:00 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 ------------------------------------------------------------------------------------------------------------------------------------ 5 PLUTO-2-REF FGS POS 3 F583W 1 20 S SAME POS AS 10; SEQ 05-70 NON-INT; MAX DUR 20S; GS ACQ SCENARIO SINGLE Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 10 PLUTO-1 FGS POS 3 F583W 1 20 S POS TARG 0.0,0.0; MAX DUR 20S Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 20 PLUTO-1 FGS TRANS 3 F583W SCANS=20,STEP-SIZE=1 1 1200 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 30 PLUTO-2-REF FGS POS 3 F583W 1 15 S MAX DUR 15S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 40 PLUTO-1-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 50 PLUTO-4-REF FGS POS 3 F583W 1 40 S MAX DUR 40S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 60 PLUTO-5-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 70 PLUTO-2-REF FGS POS 3 F583W 1 15 S MAX DUR 15S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 7494( 6) - 03/12/98 15:38 - [ 6] Visit: 02 Visit Priority: Visit Requirements: PCS MODE Fine ORIENTation 277D TO 279D BETWEEN 12-MAR-98:16:00:00 AND 12- MAR-98:20:00:00 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 ------------------------------------------------------------------------------------------------------------------------------------ 5 PLUTO-2-REF FGS POS 3 F583W 1 20 S MAX DUR 20S;SEQ 05-80 NON-INT;SAME POS AS 10 GS ACQ SCENARIO SINGLE Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 10 PLUTO-2 FGS POS 3 F583W 1 20 S POS TARG 0.0, 0.0;MAX DUR 20S Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 20 PLUTO-2 FGS TRANS 3 F583W SCANS=18,STEP-SIZE=1 1 1080 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 30 PLUTO-2-REF FGS POS 3 F583W 1 15 S MAX DUR 15S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 40 PLUTO-1-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 50 PLUTO-3-REF FGS POS 3 F583W 1 40 S MAX DUR 40S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 60 PLUTO-4-REF FGS POS 3 F583W 1 45 S MAX DUR 45S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 70 PLUTO-5-REF FGS POS 3 F583W 1 45 S MAX DUR 45S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 80 PLUTO-2-REF FGS POS 3 F583W 1 15 S MAX DUR 15S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 7494( 6) - 03/12/98 15:38 - [ 7] Visit: 03 Visit Priority: Visit Requirements: PCS MODE Fine ORIENTation 274D TO 276D SCHEDulability 40% BETWEEN 15-MAR- 98:4:00:00 AND 15-MAR-98:8:00:00 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 ------------------------------------------------------------------------------------------------------------------------------------ 5 PLUTO-2-REF FGS POS 3 F583W 1 20 S MAX DUR 20S;SEQ 05-70 NON-INT;SAME POS AS 10 GS ACQ SCENARIO SINGLE Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 10 PLUTO-3 FGS POS 3 F583W 1 30 S POS TARG 0.0, 0.0;MAX DUR 30S Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 20 PLUTO-3 FGS TRANS 3 F583W SCANS=20,STEP-SIZE=1 1 1200 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 30 PLUTO-2-REF FGS POS 3 F583W 1 20 S MAX DUR 20S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 40 PLUTO-1-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 50 PLUTO-3-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 60 PLUTO-4-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 70 PLUTO-2-REF FGS POS 3 F583W 1 20 S MAX DUR 20S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 7494( 6) - 03/12/98 15:38 - [ 8] Visit: 04 Visit Priority: Visit Requirements: PCS MODE Fine ORIENTation 273D TO 275D SCHEDulability 40% BETWEEN 15-MAR- 98:19:00:00 AND 15-MAR-98:23:00:00 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 ------------------------------------------------------------------------------------------------------------------------------------ 5 PLUTO-2-REF FGS POS 3 F583W 1 20 S MAX DUR 20S;SEQ 05-70 NON-INT;SAME POS AS 10 GS ACQ SCENARIO SINGLE Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 10 PLUTO-4 FGS POS 3 F583W 1 30 S POS TARG 0.0, 0.0;MAX DUR 30S Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 20 PLUTO-4 FGS TRANS 3 F583W SCANS=20,STEP-SIZE=1 1 1200 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 30 PLUTO-2-REF FGS POS 3 F583W 1 20 S MAX DUR 20S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 40 PLUTO-1-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 50 PLUTO-3-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 60 PLUTO-4-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 70 PLUTO-2-REF FGS POS 3 F583W 1 20 S MAX DUR 20S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 7494( 6) - 03/12/98 15:38 - [ 9] Visit: 05 Visit Priority: Visit Requirements: PCS MODE Fine ORIENTation 272D TO 274D SCHEDulability 40% BETWEEN 16-MAR- 98:15:30:00 AND 16-MAR-98:20:00:00 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 ------------------------------------------------------------------------------------------------------------------------------------ 5 PLUTO-2-REF FGS POS 3 F583W 1 20 S MAX DUR 20S;SEQ 05-70 NON-INT;SAME POS AS 10 GS ACQ SCENARIO SINGLE Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 10 PLUTO-5 FGS POS 3 F583W 1 30 S POS TARG 0.0, 0.0;MAX DUR 30S Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 20 PLUTO-5 FGS TRANS 3 F583W SCANS=20,STEP-SIZE=1 1 1200 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 30 PLUTO-2-REF FGS POS 3 F583W 1 20 S MAX DUR 20S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 40 PLUTO-1-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 50 PLUTO-3-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 60 PLUTO-4-REF FGS POS 3 F583W 1 50 S MAX DUR 50S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 70 PLUTO-2-REF FGS POS 3 F583W 1 20 S MAX DUR 20S; SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 7494( 6) - 03/12/98 15:38 - [ 10] Summary Form for Proposal 7494 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FGS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes POS TRANS ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCANS=20 STEP-SIZE=1 SCANS=18 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE Fine ORIENTation 274D TO 276D BETWEEN 12-MAR-98 4 00 00 AND 12-MAR-98 8 00 00 SAME POS AS 10; SEQ 05-70 NON-INT; MAX DUR 20S; GS ACQ SCENARIO SINGLE POS TARG 0.0,0.0; MAX DUR 20S SAME POS AS 10 MAX DUR 15S; SAME POS AS 10 MAX DUR 50S; SAME POS AS 10 MAX DUR 40S; SAME POS AS 10 PCS MODE Fine ORIENTation 277D TO 279D BETWEEN 12-MAR-98 16 00 00 AND 12-MAR-98 20 00 00 MAX DUR 20S;SEQ 05-80 NON-INT;SAME POS AS 10 GS ACQ SCENARIO SINGLE POS TARG 0.0, 0.0;MAX DUR 20S MAX DUR 45S; SAME POS AS 10 PCS MODE Fine ORIENTation 274D TO 276D SCHEDulability 40% BETWEEN 15-MAR-98 4 00 00 AND 15-MAR-98 8 00 00 MAX DUR 20S;SEQ 05-70 NON-INT;SAME POS AS 10 GS ACQ SCENARIO SINGLE POS TARG 0.0, 0.0;MAX DUR 30S MAX DUR 20S; SAME POS AS 10 PCS MODE Fine ORIENTation 273D TO 275D SCHEDulability 40% BETWEEN 15-MAR-98 19 00 00 AND 15-MAR-98 23 00 00 PCS MODE Fine ORIENTation 272D TO 274D SCHEDulability 40% BETWEEN 16-MAR-98 15 30 00 AND 16-MAR-98 20 00 00 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F583W ------------------------------------------------------------------------------------------------------------------------------------ Target Names PLUTO-2-REF PLUTO-1 PLUTO-1-REF PLUTO-4-REF PLUTO-5-REF PLUTO-2 PLUTO-3-REF PLUTO-3 PLUTO-4 PLUTO-5 ------------------------------------------------------------------------------------------------------------------------------------