7490( 4) - 05/29/97 16:35 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7490 Version: 4 Check-in Date: 29-May-1997 16:33:23 1.Proposal Title: Triton's Distorted Atmosphere ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle SOLAR SYSTEM GO 7 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: JAMES L. ELLIOT MIT CoI: Catherine B. Olkin Lowell Observatory N CoI: Otto G. Franz Lowell Observatory Y CoI: Mary A. Agner Massachusetts Institute of Technology N ------------------------------------------------------------------------------------ 6. Abstract The asymmetry of a stellar-occultation light curve for Triton observed in 1995 can be readily explained if Triton's middle atmosphere is distorted from spherical symmetry. The data require only a portion of the atmosphere near the northern or southern limbs to be flattened, but a global oblate model has an atmospheric flattening of 0.027 +/- 0.005, with a symmetry axis consistent with Triton's rotation axis. This large flattening would be totally unexpected from Triton's slow rotation (5.877 day period), but might be explained by a combination of high zonal winds (less than the sonic velocity, 140 m s^-1) and gravitational anomalies. Such winds would be consistent with the observed thermal structure, which is consistent with an adiabatic profile. More information about the figure of Triton's atmosphere can be learned by modeling the atmospheric figure with the six occultation chords, but three correspond to one component of the double star, Tr148A, and three to the other component, Tr148B. Hence current solutions use their separation and position angle as a free parameters. An accurate, independent measurement of the relative position of the two stars is necessary to use these data to establish Triton's atmospheric figure. The HST is essential for this double-star measurement because the double is too difficult for ground-based techniques of interferometry and active optics. ------------------------------------------------------------------------------------ 7490( 4) - 05/29/97 16:35 - [ 2] Observations Description ------------------------ Three observations, each requiring one orbit, will be carried out with FGS-3 and filter F583W. This will permit us to use optical field angle distortion calibrations (OFAD) and single-star transfer function calibrations available from previous cycles. Each of three visits will begin with a POS mode observation of the prime target (TR 148), followed by one POS mode observation for each of the four reference stars. We will then observe the prime target in TRANS mode, making 24 scans for a total exposure of 720 seconds (1.2 arcsec length per FGS axis). These scan parameters will produce Transfer Functions of S/N sufficient to obtain astrometry of 1-mas accuracy. The TRANS observation will be followed by another POS-mode observation of the prime target, by reobservation of the reference stars, and by one more observation of the prime target in POS-mode only. Real Time Justification ----------------------- The range of dates and spacecraft orientations specified under Special Requirements for each visit is determined by the availability of reference stars at epochs needed to determine proper motion and possible orbital motion of the prime target's components with the required accuracy. Adherence to these special scheduling requirements is therefore essential for achieving the scientific objectives of this project. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Otto Franz*1400 W. Mars Hill Rd.*Flagstaff, AZ 86001 Ship Via: Email: ogf@lowell.edu ------------------------------------------------------------------------------------ 7490( 4) - 05/29/97 16:35 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 TR148 STAR RA = 295.25160D +/- 0.00014D, J2000 V = 12.96+/-0.05 DEC = -20.86141D +/- 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 2 TR148-1-REF CALIBRATION,ASTROMETRIC RA = 295.20988D +/- 0.00014D, J2000 V = 14.24+/-0.2 DEC = -20.84834D +/- 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 3 TR148-2-REF CALIBRATION,ASTROMETRIC RA = 295.13817D +/- 0.00014D, J2000 V = 12.49+/-0.05 DEC = -20.85503D +/- 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 4 TR148-3-REF CALIBRATION,ASTROMETRIC RA = 295.31148D +/- 0.00014D, J2000 V = 13.60+/-0.05 DEC = -20.85674D +/- 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 5 TR148-4-REF CALIBRATION,ASTROMETRIC RA = 295.33411D +/- 0.00014D, J2000 V = 12.33+/-0.05 DEC = -20.85704D +/- 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 7490( 4) - 05/29/97 16:35 - [ 4] Visit: 01 Visit Requirements: PCS MODE Fine ORIENTation 82D TO 87D SCHEDulability 70% BETWEEN 19-JUL- 97:12:00:00 AND 6-AUG-97 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 ------------------------------------------------------------------------------------------------------------------------------------ 6 TR148 FGS TRANS 3 F583W SCANS=26,STEP-SIZE=1 1 780 S POS TARG 0.0,0.0;SEQ 6-120 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 10 TR148 FGS POS 3 F583W 1 25 S SAME POS AS 6 Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 20 TR148-1-REF FGS POS 3 F583W 1 35 S MAX DUR 35S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 30 TR148-2-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 40 TR148-3-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 50 TR148-4-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 70 TR148 FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 80 TR148-1-REF FGS POS 3 F583W 1 35 S MAX DUR 35S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 90 TR148-2-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 100 TR148-3-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 110 TR148-4-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 120 TR148-2-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 7490( 4) - 05/29/97 16:35 - [ 5] Visit: 02 Visit Requirements: ORIENTation 79D TO 81D BETWEEN 1-NOV-97 AND 24-NOV-97 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 ------------------------------------------------------------------------------------------------------------------------------------ 6 TR148 FGS TRANS 3 F583W SCANS=24,STEP-SIZE=1 1 720 S POS TARG 0.0,0.0;SEQ 6-120 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 10 TR148 FGS POS 3 F583W 1 25 S SAME POS AS 6 Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 20 TR148-1-REF FGS POS 3 F583W 1 35 S MAX DUR 35S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 30 TR148-2-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 40 TR148-3-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 50 TR148-4-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 70 TR148 FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 80 TR148-1-REF FGS POS 3 F583W 1 35 S MAX DUR 35S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 90 TR148-2-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 100 TR148-3-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 110 TR148-4-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 120 TR148-2-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 7490( 4) - 05/29/97 16:35 - [ 6] Visit: 03 Visit Requirements: ORIENTation 80D TO 81D BETWEEN 1-OCT-98 AND 31-OCT-98 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 ------------------------------------------------------------------------------------------------------------------------------------ 6 TR148 FGS TRANS 3 F583W SCANS=24,STEP-SIZE=1 1 720 S POS TARG 0.0,0.0;SEQ 6-120 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 10 TR148 FGS POS 3 F583W 1 25 S SAME POS AS 6 Comments: OBSERVATION MAY BE TRUNCATED TO SATISFY MONITORING SPACING REQUIREMENTS ------------------------------------------------------------------------------------------------------------------------------------ 20 TR148-1-REF FGS POS 3 F583W 1 35 S MAX DUR 35S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 30 TR148-2-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 40 TR148-3-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 50 TR148-4-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 70 TR148 FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 80 TR148-1-REF FGS POS 3 F583W 1 35 S MAX DUR 35S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 90 TR148-2-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 100 TR148-3-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 110 TR148-4-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 120 TR148-2-REF FGS POS 3 F583W 1 10 S MAX DUR 10S; SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 7490( 4) - 05/29/97 16:35 - [ 7] Summary Form for Proposal 7490 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FGS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TRANS POS ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCANS=26 STEP-SIZE=1 SCANS=24 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE Fine ORIENTation 82D TO 87D SCHEDulability 70% BETWEEN 19-JUL-97 12 00 00 AND 6-AUG-97 POS TARG 0.0,0.0;SEQ 6-120 NON-INT SAME POS AS 6 MAX DUR 35S; SAME POS AS 6 MAX DUR 10S; SAME POS AS 6 ORIENTation 79D TO 81D BETWEEN 1-NOV-97 AND 24-NOV-97 ORIENTation 80D TO 81D BETWEEN 1-OCT-98 AND 31-OCT-98 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F583W ------------------------------------------------------------------------------------------------------------------------------------ Target Names TR148 TR148-1-REF TR148-2-REF TR148-3-REF TR148-4-REF ------------------------------------------------------------------------------------------------------------------------------------