Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 3373c Report Date: 09-May-96:18:33 Version: ********** Check-in Date: ********** 1.Proposal Title: THE SIZE AND COMPOSITION OF PLANETARY RING PARTICLES - CYC2HIGH ------------------------------------------------------------------------------------ 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: 3.97 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 3373c PI: Robert C. Bless Proposal Title: THE SIZE AND COMPOSITION OF PLANETARY RING PARTICLES - CYC2HIGH ------------------------------------------------------------------------------------ 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 onboard acquisition to verify the guide stars; (ii) a scan of about ten 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 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 telescopes. ------------------------------------------------------------------------------------ 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, a prior scan over 10 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 DEC 5000 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 = 3373c [ 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| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 10 GSC5800- A,126 PLATE-ID = 00WO, J2000 BKG 1 B = 12.5 +/- 0.5 00460 RA = 21H 47M 02.947S +/- 0.01", DEC = -14D 58' 58.18" +/- 0.03", Comments: STAR TO BE OCCULTED BY SATURN. CLOSE APPROACH AT 12-OCT-93:07:39 SOLAR ELONG 125D ------------------------------------------------------------------------------------------------------------------------------------ 11 00460-OFFSET A,126 RA = 21H 47M 05.430S +/- J2000 1 B = 17.0 +/- 0.2 STAR-2147- 0.04", 1500 DEC = -14D 59' 53.23" +/- 0.04", Comments: OFFSET TARGET FOR GSC5800-00460 ------------------------------------------------------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 3373c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 14 | TARGET NAME: 00460-BACKGROUND ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: OFFSET SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = SATURN | TYPE = POS_ANGLE, | RAD = 19.67, | ANG = 78.5, | 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 | ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 3373c [ 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 # HSP/ ACQ 1 1S 1 1 ONBRD- VIS ACQ ------------------------------------------------------------------------------------------------------------------------------------ 6 DEFINE # HSP/ SPLIT 1.0 F750W/ # 1 1S 1 1 SPATIAL SCAN BACK- PMT/ F320N SCAN VIS ------------------------------------------------------------------------------------------------------------------------------------ 7 DEFINE # HSP/ SPLIT 1.0 F750W/ # 1 1M 1 1 RING- PMT/ F320N OCC VIS ------------------------------------------------------------------------------------------------------------------------------------ 7.5 DEFINE ^ S/C DATA NONE FORMAT=FN 1 0M 1 PAR WITH 7.0 RING- OCC Comments: CAPTURE FGS TLM DURING OCCULTATION. ------------------------------------------------------------------------------------------------------------------------------------ 10.01 USE 00460- SAMPLE- X454 SEQ 10.01 - 10.07 BACK- BACKGROUND TIME=0.01 GROUP 10.01 - SCAN DATA-FORMAT=ALL 10.09 WITHIN 9H PMT-ANALOG=1000 CYCLE 2/10.01 - VIS-ANALOG=100 10.32 ------------------------------------------------------------------------------------------------------------------------------------ 10.03 USE 00460- SAMPLE- X454 BACK- BACKGROUND TIME=0.01 SCAN DATA-FORMAT=ALL PMT-ANALOG=1000 VIS-ANALOG=100 ------------------------------------------------------------------------------------------------------------------------------------ 10.07 USE 00460- SAMPLE- X454 BACK- BACKGROUND TIME=0.01 SCAN DATA-FORMAT=ALL PMT-ANALOG=1000 VIS-ANALOG=100 ------------------------------------------------------------------------------------------------------------------------------------ 10.09 USE 00460- X240 ONBOARD ACQ FOR ONBRD- OFFSET 10.100-10.102 ACQ PCS MODE F / 10.09 - 10.102 Comments: USE FINE LOCK ONLY. IF BRIGHT ENOUGH GUIDE STARS CANNOT BE FOUND, CANCEL OBSERVATION. ------------------------------------------------------------------------------------------------------------------------------------ 10.1 USE GSC5800- SAMPLE- X36 AT 12-OCT-93:09:31 RING- 00460 TIME=0.01 +/- 1M OCC DATA-FORMAT=ALL SEQ 10.100-10.102 PMT-ANALOG=1000 NO GAP VIS-ANALOG=100 RT ANALYSIS SEQ 10.09 - 10.10 NO GAP ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 3373c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10.1 USE GSC5800- SAMPLE- X36 RT ANALYSIS RING- 00460 TIME=0.01 OCC DATA-FORMAT=ALL PMT-ANALOG=1000 VIS-ANALOG=100 ------------------------------------------------------------------------------------------------------------------------------------ 10.1 USE GSC5800- SAMPLE- X36 GROUP 10.102 - RING- 00460 TIME=0.01 10.32 WITHIN 9H OCC DATA-FORMAT=ALL RT ANALYSIS PMT-ANALOG=1000 VIS-ANALOG=100 Comments: END EXPOSURE AT 12-OCT- 93:11:20. ------------------------------------------------------------------------------------------------------------------------------------ 10.26 USE 00460- SAMPLE- X454 SEQ 10.26 - 10.32 BACK- BACKGROUND TIME=0.01 SCAN DATA-FORMAT=ALL PMT-ANALOG=1000 VIS-ANALOG=100 ------------------------------------------------------------------------------------------------------------------------------------ 10.28 USE 00460- SAMPLE- X454 BACK- BACKGROUND TIME=0.01 SCAN DATA-FORMAT=ALL PMT-ANALOG=1000 VIS-ANALOG=100 ------------------------------------------------------------------------------------------------------------------------------------ 10.32 USE 00460- SAMPLE- X454 BACK- BACKGROUND TIME=0.01 SCAN DATA-FORMAT=ALL PMT-ANALOG=1000 VIS-ANALOG=100 ------------------------------------------------------------------------------------------------------------------------------------ Scan Paramters Form Proposal ID: 3373c [ 8] ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 1 Exposure Logsheet lines: 10.01, 10.07, 10.26, FGS Scan: CONTINUOUS Dwell Only: dwell points/line: 0 Seconds per dwell: 0.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 34.0000 Angle between sides (degrees) 90.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0750 PA of first scan line (degrees) 253.300 Scan frame (CEL or S/C): CEL Length Offset (arc-sec): 0. Width Offset (arc-sec): 0 ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 2 Exposure Logsheet lines: 10.03, 10.28 FGS Scan: CONTINUOUS Dwell Only: dwell points/line: 0 Seconds per dwell: 0.00 Scan width (arc-secs): 2.0000 Scan length (arc-secs): 34.0000 Angle between sides (degrees) 90.00 Number of lines: 5 Scan rate (arc-sec/sec): 0.0750 PA of first scan line (degrees) 253.300 Scan frame (CEL or S/C): CEL Length Offset (arc-sec): 0. Width Offset (arc-sec): 1.0000 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 3373c [ 9] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HSP/VIS HSP/PMT/VIS S/C ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ SPLIT DATA ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FORMAT=FN SAMPLE-TIME DATA-FORMAT PMT-ANALOG VIS-ANALOG ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GTO/HSP ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 3.97 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SPATIAL SCAN; PAR WITH 7.0; SEQ 10.01 - 10.07; GROUP 10.01 - 10.09 WITHIN 9H; CYCLE 2/10.01 - 10.32; ONBOARD ACQ FOR 10.100-10.102; PCS MODE F / 10.09 - 10.102; AT 12-OCT-93 09 31 +/- 1M; SEQ 10.100-10.102 NO GAP; RT ANALYSIS; SEQ 10.09 - 10.10 NO GAP; GROUP 10.102 - 10.32 WITHIN 9H; SEQ 10.26 - 10.32; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F750W/F320N ------------------------------------------------------------------------------------------------------------------------------------ Target Names GSC5800-00460 00460-OFFSET STAR-2147-1500 00460-BACKGROUND ------------------------------------------------------------------------------------------------------------------------------------