6753( 5) - 02/17/97 10:21 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6753 Version: 5 Check-in Date: 17-Feb-1997 10:14:50 1.Proposal Title: Recovery of Inner Satellites of Neptune ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle SOLAR SYSTEM GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: P. Kenneth Seidelmann US Naval Observatory CoI: James Rohde United States Naval Observatory N CoI: Alex Storrs Space Telescope Science Institute N CoI: Eddie Wells Computer Sciences Corporation N CoI: Ben Zellner Georgia Southern University N CoI: Amanda Bosh Lowell Observatory N CoI: Douglas Currie University of Maryland N CoI: Dan Pascu United States Naval Observatory N ------------------------------------------------------------------------------------ 6. Abstract Six small inner satellites of Neptune were discovered by Voyager 2 in 1989, and none of them have been observed since. The orbital positions of these inner satellites are currently uncertain by up to 27 degrees. Color measurements over a very limited wavelength range were obtained only for Proteus. We propose to recover these satellites using the strategy that we used successfully in recovering the inner satellites of Uranus in Cycle 4 Program GO-5321. Deep WFPC2 exposures with wide filters that allow Neptune to saturate, but not bloom significantly, allow detection and, most importantly, precise measurement of positions for calculating accurate mean motions and improved orbital elements. The accurate mean motions and ephemerides will allow the study of dynamical relationships between the satellites and rings and, in future HST cycles, observations of the satellites with NICMOS or other HST instruments. By scheduling the maximum number of exposures in each orbit, B-V and V-I colors can be measured for most of the satellites and supply new information about their compositions. Although not our main objective, the ring arcs of Neptune may be visible on our deeper exposures, as was true for Uranian rings in Program GO-5321. If so, they could finally establish whether the ring arcs are stable over long periods and offer some clues to the composition of the constituent particles. ------------------------------------------------------------------------------------ 6753( 5) - 02/17/97 10:21 - [ 2] Observations Description ------------------------ We propose to use three HST orbits to take three identical series of 13 images with the Planetary Camera centered on Neptune. There would be 3 exposures using filter F439W (80, 100 and 160 S), 5 exposures using filter F555W (10, 20, 40, 40 and 40 S), and 5 exposures using F791W (16, 35, 160, 160, and 160S). The filters are transformable to standard B, V, and I and, except for dropping the R filter, are similar to the set used to image the inner satellites of Uranus in Cycle 4. RPS2 was used to confirm that the exposures are possible in a 53 minute visibility period. For each filter two short exposures will be taken to obtain unsaturated images of Neptune, Triton and Proteus for determination of the scale and orientation of the images and for photometric calibration. A third exposure for filter F555W will be the deepest possible without allowing the image of Neptune to bloom and obscure close satellites. The count rates for F439W are too low for blooming to be an issue. The time required for the innermost satellites to move a distance of one PC pixel while tracking on Neptune (80 seconds) provides a limit on the longest useful exposure times. In order to reach the faintest inner satellites and the rings, our longest exposures will be 100 or 160 seconds, during which the inner satellites will move 1.5 or 2 pixels. Real Time Justification ----------------------- Visits 2 and 3 should follow visit 1 by 6.4 and 73.9 hours, which will allow unambiguous identification of the satellites and will ensure that each satellite be imaged at an advantageous position in its orbit and with respect to the diffraction pattern of the HST spiders. Moving-target tracking of Neptune near the center of the field will be required. We will require that Triton (maximum elongation 17") be always visible on the PC image and not too near the edge, which will be true over about 80 percent of its 6-day orbit. Nereid will also be near conjunction with the planet near the beginning and end of Cycle 6. Its presence in the image would be advantageous but not strictly necessary. Otherwise the system can be imaged at any time when it is not in the solar avoidance zone. However, Neptune is at opposition on 21 July 1997 and is a good candidate for early scheduling. The best results would be obtained from observations within a few weeks of opposition. No supporting observations are required. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: STSCI Ship Via: Email: wells@stsci.edu ------------------------------------------------------------------------------------ 6753( 5) - 02/17/97 10:21 - [ 3] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: NEPTUNE-W ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET NEPTUNE ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=NEPTUNE | TYPE=POS_ANGLE,RAD=5,ANG=180,REF=SUN,EPO | CH=01-Jan-1997 | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | OLG OF TRITON FROM EARTH BETWEEN 45 135 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | TYPE=G2V | Target is Neptune with Triton near V = 7.9+/-0.1 | western elongation Triton must be in | the PC for all images and should be | at least 5 arcsec from the edge. | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: NEPTUNE-E ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET NEPTUNE ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=NEPTUNE | TYPE=POS_ANGLE,RAD=5,ANG=0,REF=SUN,EPOCH | =01-Jan-1997 | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | OLG OF TRITON FROM EARTH BETWEEN 225 315 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | TYPE=G2V | Target is Neptune with Triton near V = 7.9+/-0.1 | eastern elongation. Triton must be | in PC for all exposures. | ------------------------------------------------------------------------------------------------------------------------------------ 6753( 5) - 02/17/97 10:21 - [ 4] Visit: 01 Visit Requirements: BETWEEN 21-Jun-1997 AND 21-Jul-1997 SCHED 60% ORIENT -5D TO 5D FROM NOMINAL On Hold Comments: Additional Comments: Please manually merge this visit to force the moving target track change to occur between Exposures 75 and 80. These visits are set up to be scheduled between June 21, 1977 and July 21, 1997 when Neptune is at opposition. The 4 week period after July 21 would be equally good, but we were not able to define the pointing in a way that worked for both periods. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 NEPTUNE-W WFPC2 IMAGE PC1-FIX F439W ATD-GAIN=15 1 80 S SEQ 10-120 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 20 NEPTUNE-W WFPC2 IMAGE PC1-FIX F439W ATD-GAIN=15 1 100 S ------------------------------------------------------------------------------------------------------------------------------------ 30 NEPTUNE-W WFPC2 IMAGE PC1-FIX F439W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 40 NEPTUNE-W WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 10 S ------------------------------------------------------------------------------------------------------------------------------------ 50 NEPTUNE-W WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 20 S ------------------------------------------------------------------------------------------------------------------------------------ 60 NEPTUNE-W WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=7 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 70 NEPTUNE-W WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=7 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 75 NEPTUNE-W WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=7 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 80 NEPTUNE-W WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=15 1 16 S ------------------------------------------------------------------------------------------------------------------------------------ 90 NEPTUNE-W WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=15 1 35 S ------------------------------------------------------------------------------------------------------------------------------------ 100 NEPTUNE-W WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 110 NEPTUNE-W WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 120 NEPTUNE-W WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 6753( 5) - 02/17/97 10:21 - [ 5] Visit: 02 Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 370 M TO 400 M SCHED 60% On Hold Comments: Additional Comments: Please manually merge this visit to force the moving target track change to occur between Exposures 275 and 280. This visit should be scheduled 4 orbits after visit 01. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 210 NEPTUNE-W WFPC2 IMAGE PC1-FIX F439W ATD-GAIN=15 1 80 S SEQ 210-320 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 220 NEPTUNE-W WFPC2 IMAGE PC1-FIX F439W ATD-GAIN=15 1 100 S ------------------------------------------------------------------------------------------------------------------------------------ 230 NEPTUNE-W WFPC2 IMAGE PC1-FIX F439W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 240 NEPTUNE-W WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 10 S ------------------------------------------------------------------------------------------------------------------------------------ 250 NEPTUNE-W WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 20 S ------------------------------------------------------------------------------------------------------------------------------------ 260 NEPTUNE-W WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=7 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 270 NEPTUNE-W WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=7 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 275 NEPTUNE-W WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=7 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 280 NEPTUNE-W WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=15 1 16 S ------------------------------------------------------------------------------------------------------------------------------------ 290 NEPTUNE-W WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=15 1 35 S ------------------------------------------------------------------------------------------------------------------------------------ 300 NEPTUNE-W WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 310 NEPTUNE-W WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 320 NEPTUNE-W WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 6753( 5) - 02/17/97 10:21 - [ 6] Visit: 03 Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 73.6 H TO 74.2 H SCHED 60% On Hold Comments: Additional Comments: Please manually merge this to force the moving target track change to occur between Exposures 475 and 480. Visit should be scheduled 46 orbits after visit 01. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 410 NEPTUNE-E WFPC2 IMAGE PC1-FIX F439W ATD-GAIN=15 1 80 S SEQ 410-520 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 420 NEPTUNE-E WFPC2 IMAGE PC1-FIX F439W ATD-GAIN=15 1 100 S ------------------------------------------------------------------------------------------------------------------------------------ 430 NEPTUNE-E WFPC2 IMAGE PC1-FIX F439W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 440 NEPTUNE-E WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 10 S ------------------------------------------------------------------------------------------------------------------------------------ 450 NEPTUNE-E WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15 1 20 S ------------------------------------------------------------------------------------------------------------------------------------ 460 NEPTUNE-E WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=7 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 470 NEPTUNE-E WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=7 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 475 NEPTUNE-E WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=7 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 480 NEPTUNE-E WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=15 1 16 S ------------------------------------------------------------------------------------------------------------------------------------ 490 NEPTUNE-E WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=15 1 35 S ------------------------------------------------------------------------------------------------------------------------------------ 500 NEPTUNE-E WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 510 NEPTUNE-E WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 520 NEPTUNE-E WFPC2 IMAGE PC1-FIX F791W ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 6753( 5) - 02/17/97 10:21 - [ 7] Summary Form for Proposal 6753 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ATD-GAIN=15 ATD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 21-Jun-1997 AND 21-Jul-1997 SCHED 60% ORIENT -5D TO 5D FROM NOMINAL SEQ 10-120 NON-INT SAME ORIENT AS 01 AFTER 01 BY 370 M TO 400 M SCHED 60% SEQ 210-320 NON-INT SAME ORIENT AS 01 AFTER 01 BY 73.6 H TO 74.2 H SCHED 60% SEQ 410-520 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F439W F555W F791W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NEPTUNE-W NEPTUNE-E ------------------------------------------------------------------------------------------------------------------------------------