Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 1080c Report Date: 09-May-96:16:07 Version: ********** Check-in Date: ********** 1.Proposal Title: THE SIZE AND COMPOSITION OF PLANETARY RING PARTICLES ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID SOLAR SYSTEM GTO/HSP 1080 Sub Category ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Robert C. Bless WISCONSIN, UNIVERSITY OF USA 608-262-1715 ------------------------------------------------------------------------------------ 7. Abstract The size and composition of planetary ring particles are of interest for two reasons. First, these parameters provide important clues as to the age and source of the particles. The second reason for the interest in the size and composition of ring particles is that these quantities determine the fate of the particles in their present environment. In this regard, the size of the particles tells us the relative importance of gravitational forces (resonances with satellites, gravitational interaction with other ring particles, and the planetary gravity potential) and non- gravitational forces (particle collisions, radiation drag, and electromagnetic forces) in the present dynamical evolution. Clearly, the sizes and compositions of ring particles are central to our understanding of ring systems. Using the unique capabilities of ST, we propose to make major advances in knowledge of the size and composition of planetary ring particles through a combination of spectral and occultation ------------------------------------------------------------------------------------ 8. Scientific Key Words: PLANETARY RINGS, RING PARTICLES, OCCULTATIONS, RINGS SPECTRA, RING COMPOSITION ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 4.07 par: 0 10. Num targs pri: 8 par: 0 ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 1080c PI: Robert C. Bless Proposal Title: THE SIZE AND COMPOSITION OF PLANETARY RING PARTICLES ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Edward L. Robinson TEXAS, UNIVERSITY OF USA Robert C. Bless WISCONSIN, UNIVERSITY OF USA G. W. Van Citters NATIONAL SCIENCE FOUNDATION USA Joseph F. Dolan NASA, GODDARD SPACE FLIGHT USA CENTER Richard L. White SPACE TELESCOPE SCIENCE USA INSTITUTE James L. Elliot MASSACHUSETTS INSTITUTE OF USA TECHNOLOGY ------------------------------------------------------------------------------------ 3. Description of proposed observations. The observing program for this project consists of two parts: occultation observations and spectral observations. For the occultations, we plan to use the ST orbit parameters and the ephemerides of the known ringed planets to identify those occultations of sufficient signal-to-noise ratio to achieve the goals outlined in Section 2. Each observation will require (i) an acquisition to verify the guide stars; (ii) a scan of about 50 arc-seconds along the track that the object will follow relative to the planet to determine the planetary contribution to the background; and (iii) a time series run on the object with whatever filter -aperture conbination (or the FOS, if that would prove to be the more appropriate instrument) that is chosen for the observation. For some occultations to be observed in the far UV, prior multi-filter photometry of the object will be necessary in order to determine the most appropriate filter (and instrument, the HSP or FOS) to use for the occultation. For now, we shall For the Jovian and Uranian rings, we are proposing to obtain a spectrum at each of two locations in the ring system at five different phase angles. Three of the phase angles would be selected near opposition to define the opposition surge, and the other two would be selected to uniformly cover the range of phase angles accessible with the ST. To facilitate a direct comparison of our results with Saturn's rings, we are proposing to obtain spectra at seven locations (the A, B, C, D, E, F, and G rings) at a single phase angle. Uranian and Jovian exposures: 20 minutes each; Saturnian exposures: about five minutes. occultations in any cycle; spectra after cycle 1. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. We can achieve a much better signal-to-noise ratio for determining the optical depths of the ring systems by observing these occultations with the ST than would be possible from the ground for the following reasons: (i) the lower level of background scattered light seen by the ST; (ii) our ability to reject background light by employing small focal plane apertures; (iii) the absence of scintillation noise, which has strong components at frequencies comparable to the occultation timescale; and (iv) the much greater span of wavelengths that can be covered--well into the UV for occultations of stars of early spectral type. High- quality spectra of the Uranian rings, Jovian rigns, and the D, E, F, and G rings of Saturn are not obtainable with ground-based ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. For occultations, acquisition of the star near the planet may be difficult. Page 3 ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. For occultations, an early acquisition to verify the guide stars and a prior scan over ten arc-seconds is needed to map the scattered light field (needed for the data reduction). ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. Data will be reduced and analyzed at MIT with the VAX 11-750 belonging to the planetary astronomy group. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). TBD ------------------------------------------------------------------------------------ 13. Information about the size distribution, shape, and composition of ring particles can be obtained from observations of stellar occultations by planetary rings with the HSP and spectral imaging with the FOS, over the range of solar phase angles accessible from earth. These quantities provide information about the ages and sources of the particles and the interaction of the particles with the present dynamical state. ------------------------------------------------------------------------------------ 11. Address Information Name: ROBERT C. BLESS Category: PI Institution: UNIVERSITY OF WISCONSIN Address: DEPT. OF ASTRONOMY City: MADISON State: WI Zip Code: 53706 Country: USA Telephone: 608-262-1715 Telex (or e-mail): ------------------------------------------------------------------------------------ Name: JAMES L. ELLIOT Category: CON Institution: MASSACHUSETTS INSTITUTE OF TECHNO Address: BLDG. 54-422 City: CAMBRIDGE State: MA Zip Code: 02139 Country: USA Telephone: 617-253-6308 Telex (or e-mail): 921473 MIT CAM ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 1080c [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 20 AGK+08D1425 A,140 PLATE-ID = 0258, J2000 BKG 1 V = 9.7 +/- 0.1 GSC846-01172 RA = 10H 51M 54.901S +/- 2 B = 10.2 +/- 0.1 0.08", 3 R = 9.5 +/- 0.1 DEC = 8D 26' 5.56" +/- 0.1", 4 I = 9.3 +/- 0.3 Comments: SOLAR ELONG 54D STAR TO BE OCCULTED BY JUPITER CLOSE APPROACH AT 8-JUL-92:22:10 ------------------------------------------------------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 1080c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 10 | TARGET NAME: AGK+08D1425-BACKGROUND ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: OFFSET JUPITER ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = JUPITER | TYPE = POS_ANGLE, | RAD = 53.1, | ANG = 114, | REF = NORTH | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | | | FOR USE IN A SCAN OF BACKGROUND | | LEVELS ALONG THE PATH OF THE | | OCCULTED STAR | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 12 | TARGET NAME: AGK-BKG2 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: OFFSET JUPITER ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = JUPITER, ACQ = 0.1 | TYPE=POS_ANGLE, | RAD=68.0, | ANG=114, | REF=NORTH | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |SURF(V) = 5.4 +/- 0.5 | FOR USE IN A SCAN OF BACKGROUND | | LEVELS ALONG THE PATH OF THE | | OCCULTED STAR | ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 1080c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 4 DEFINE # FOS/RD ACQ/ 4.3 G650L 1 0.1S 1 ONBOARD ACQ FOR FOS-ACQ PEAK 4.100 SPATIAL SCAN ------------------------------------------------------------------------------------------------------------------------------------ 4.1 DEFINE # FOS/RD ACQ/ 1.0 G650L 1 0.1S 1 ONBOARD ACQ FOR FOS-ACQ PEAK 4.200 SPATIAL SCAN ------------------------------------------------------------------------------------------------------------------------------------ 4.2 DEFINE # FOS/RD ACQ/ 0.5 G650L SCAN-STEP=0.35 1 0.1S 1 FOS-ACQ PEAK SEARCH-SIZE=3 ------------------------------------------------------------------------------------------------------------------------------------ 6 DEFINE # FOS/RD RAPID 1.0 G650L 3750- READ-TIME=1.0 1 1M 1 SPATIAL SCAN FOS- 8715 SUB-STEP=1 SCAN COMB=NO Comments: USE FINE LOCK FOR OFFSET TARGET ACQ IF BRIGHT ENOUGH GUIDE STARS CAN BE FOUND. IF NOT, COARSE TRACK IS ACCEPTABLE. ------------------------------------------------------------------------------------------------------------------------------------ 110.04 USE FOS AGK+08D1425 X5 ONBOARD ACQ FOR -ACQ 110.09 SEQ 110.04 - 110.09 NO GAP CYCLE 2 / 110.04 - 110.18 ------------------------------------------------------------------------------------------------------------------------------------ 110.09 AGK+08D1425 FOS/RD RAPID 1.0 G650L 3750- READ-TIME=1.0 1 34M 1 1 CRIT OBS 8715 SUB-STEP=1 PCS MODE F COMB=NO AT 8-JUL-92:20:51 +/- 1M SEQ 110.09 - 110.18 NO GAP Comments: USE FINE LOCK FOR OFFSET TARGET ACQ IF BRIGHT ENOUGH GUIDE STARS CAN BE FOUND. IF NOT, COARSE TRACK IS ACCEPTABLE. ------------------------------------------------------------------------------------------------------------------------------------ 110.1 AGK+08D1425 FOS/RD RAPID 1.0 G650L 3750- READ-TIME=1.0 1 38M 1 1 CRIT OBS 8715 SUB-STEP=1 PCS MODE F COMB=NO Comments: END EXPOSURE AT 8-JUL-92:23:30 ------------------------------------------------------------------------------------------------------------------------------------ 110.16 USE FOS AGK+08D1425 X13 SEQ 110.16 - -SCAN -BACKGROUND 110.18 GROUP 110.09 - 110.18 WITHIN 9H ------------------------------------------------------------------------------------------------------------------------------------ 110.17 USE FOS AGK-BKG2 X13 -SCAN ------------------------------------------------------------------------------------------------------------------------------------ 110.18 USE FOS AGK-BKG2 X13 -SCAN ------------------------------------------------------------------------------------------------------------------------------------ Scan Paramters Form Proposal ID: 1080c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 1 Exposure Logsheet lines: 4.00 FGS Scan: DWELL Dwell Only: dwell points/line: 3 Seconds per dwell: 1.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 2.8000 Angle between sides (degrees) 90.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 0.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 1.4000 Width Offset (arc-sec): 0.00 ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 2 Exposure Logsheet lines: 4.1 FGS Scan: DWELL Dwell Only: dwell points/line: 6 Seconds per dwell: 1.00 Scan width (arc-secs): 0.7000 Scan length (arc-secs): 3.5000 Angle between sides (degrees) 90.00 Number of lines: 2 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 90.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 1.7500 Width Offset (arc-sec): 0.3500 ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 3 Exposure Logsheet lines: 110.16 FGS Scan: CONTINUOUS Dwell Only: dwell points/line: 0 Seconds per dwell: 0.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 84.2000 Angle between sides (degrees) 90.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0750 PA of first scan line (degrees) 293.000 Scan frame (CEL or S/C): CEL Length Offset (arc-sec): 0. Width Offset (arc-sec): 0. ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 4 Exposure Logsheet lines: 110.17 FGS Scan: CONTINUOUS Dwell Only: dwell points/line: 0 Seconds per dwell: 0.00 Scan width (arc-secs): 3.0000 Scan length (arc-secs): 69.1000 Angle between sides (degrees) 90.00 Number of lines: 5 Scan rate (arc-sec/sec): 0.0750 PA of first scan line (degrees) 293.000 Scan frame (CEL or S/C): CEL Length Offset (arc-sec): 0. Width Offset (arc-sec): 1.5000 ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 5 Exposure Logsheet lines: 110.18 FGS Scan: CONTINUOUS Dwell Only: dwell points/line: 0 Seconds per dwell: 0.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 69.1000 Angle between sides (degrees) 90.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0750 PA of first scan line (degrees) 293.000 Scan frame (CEL or S/C): CEL Length Offset (arc-sec): 0 Width Offset (arc-sec): 0 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 1080c [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK RAPID ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP=0.35 SEARCH-SIZE=3 READ-TIME=1.0 SUB-STEP=1 COMB=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GTO/HSP ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 4.07 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 4.100; SPATIAL SCAN; ONBOARD ACQ FOR 4.200; ONBOARD ACQ FOR 110.09; SEQ 110.04 - 110.09 NO GAP; CYCLE 2 / 110.04 - 110.18; CRIT OBS; PCS MODE F; AT 8-JUL-92 20 51 +/- 1M; SEQ 110.09 - 110.18 NO GAP; SEQ 110.16 - 110.18; GROUP 110.09 - 110.18 WITHIN 9H; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G650L ------------------------------------------------------------------------------------------------------------------------------------ Target Names AGK+08D1425 GSC846-01172 AGK+08D1425-BACKGROUND AGK-BKG2 ------------------------------------------------------------------------------------------------------------------------------------