! File: 4949C.PROP ! Database: PEPDB ! Date: 23-FEB-1994:11:58:04 coverpage: title_1: THE SIZE AND COMPOSITION OF PLANETARY RING PARTICLES - CYC2HIGH sci_cat: SOLAR SYSTEM proposal_for: GTO/HSP cont_id: 1080 pi_fname: ROBERT pi_mi: C. pi_lname: BLESS pi_inst: WISCONSIN, UNIVERSITY OF pi_country: USA pi_phone: 608-262-1715 keywords_1: PLANETARY RINGS, RING PARTICLES, OCCULTATIONS, RINGS keywords_2: SPECTRA, RING COMPOSITION hours_pri: 3.97 num_pri: 1 realtime: X time_crit: Y ! end of coverpage abstract: line_1: The size and composition of planetary ring particles line_2: are of interest for two reasons. First, these line_3: parameters provide important clues as to the age and line_4: source of the particles. The second reason for the line_5: interest in the size and composition of ring line_6: particles is that these quantities determine the line_7: fate of the particles in their present environment. line_8: In this regard, the size of the particles tells us line_9: the relative importance of gravitational forces line_10: (resonances with satellites, gravitational line_11: interaction with other ring particles, and the line_12: planetary gravity potential) and non-gravitational line_13: forces (particle collisions, radiation drag, and line_14: electromagnetic forces) in the present dynamical line_15: evolution. Clearly, the sizes and compositions of line_16: ring particles are central to our understanding of line_17: ring systems. Using the unique capabilities of ST, line_18: we propose to make major advances in knowledge of line_19: the size and composition of planetary ring particles line_20: through a combination of spectral and occultation ! ! end of abstract general_form_proposers: lname: ROBINSON fname: EDWARD mi: L. inst: TEXAS, UNIVERSITY OF country: USA ! lname: BLESS fname: ROBERT mi: C. inst: WISCONSIN, UNIVERSITY OF country: USA ! lname: VAN CITTERS fname: G. mi: W. inst: NATIONAL SCIENCE FOUNDATION country: USA ! lname: DOLAN fname: JOSEPH mi: F. inst: NASA, GODDARD SPACE FLIGHT CENTER country: USA ! lname: WHITE fname: RICHARD mi: L. inst: SPACE TELESCOPE SCIENCE INSTITUTE country: USA ! lname: ELLIOT fname: JAMES mi: L. inst: MASSACHUSETTS INSTITUTE OF TECHNOLOGY country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: The observing program for this project consists of line_2: two parts: occultation observations and spectral line_3: observations. For the occultations, we plan to use line_4: the ST orbit parameters and the ephemerides of the line_5: known ringed planets to identify those occultations line_6: of sufficient signal-to-noise ratio to achieve the line_7: goals outlined in Section 2. Each observation will line_8: require (i) an onboard acquisition to verify the line_9: guide stars; (ii) a scan of about ten arc-seconds line_10: along the track that the object will follow relative line_11: to the planet to determine the planetary line_12: contribution to the background; and (iii) a time line_13: series run on the object with whatever line_14: filter-aperture conbination (or the FOS, if that line_15: would prove to be the more appropriate instrument) line_16: that is chosen for the observation. For some line_17: occultations to be observed in the far UV, prior line_18: multi-filter photometry of the object will be line_19: necessary in order to determine the most appropriate line_20: filter (and instrument, the HSP or FOS) to use for ! question: 3 section: 2 line_1: For the Jovian and Uranian rings, we are proposing line_2: to obtain a spectrum at each of two locations in the line_3: ring system at five different phase angles. Three of line_4: the phase angles would be selected near opposition line_5: to define the opposition surge, and the other two line_6: would be selected to uniformly cover the range of line_7: phase angles accessible with the ST. To facilitate a line_8: direct comparison of our results with Saturn's line_9: rings, we are proposing to obtain spectra at seven line_10: locations (the A, B, C, D, E, F, and G rings) at a line_11: single phase angle. Uranian and Jovian exposures: 20 line_12: minutes each; Saturnian exposures: about five line_13: minutes. occultations in any cycle; spectra after line_14: cycle 1. ! question: 4 section: 1 line_1: We can achieve a much better signal-to-noise ratio line_2: for determining the optical depths of the ring line_3: systems by observing these occultations with the ST line_4: than would be possible from the ground for the line_5: following reasons: (i) the lower level of background line_6: scattered light seen by the ST; (ii) our ability to line_7: reject background light by employing small focal line_8: plane apertures; (iii) the absence of scintillation line_9: noise, which has strong components at frequencies line_10: comparable to the occultation timescale; and (iv) line_11: the much greater span of wavelengths that can be line_12: covered--well into the UV for occultations of stars line_13: of early spectral type. High-quality spectra of the line_14: Uranian rings, Jovian rigns, and the D, E, F, and G line_15: rings of Saturn are not obtainable with ground-based line_16: telescopes. ! question: 5 section: 1 line_1: For occultations, acquisition of the star near the line_2: planet may be difficult. ! question: 6 section: 1 line_1: For occultations, a prior scan over 10 arc-seconds line_2: is needed to map the scattered light field (needed line_3: for the data reduction). ! question: 7 section: 1 line_1: Data will be reduced and analyzed at MIT with the line_2: DEC 5000 belonging to the planetary astronomy line_3: group. ! question: 10 section: 1 line_1: TBD ! question: 13 section: 1 line_1: Information about the size distribution, shape, and line_2: composition of ring particles can be obtained from line_3: observations of stellar occultations by planetary line_4: rings with the HSP and spectral imaging with the line_5: FOS, over the range of solar phase angles accessible line_6: from earth. These quantities provide information line_7: about the ages and sources of the particles and the line_8: interaction of the particles with the present line_9: dynamical state. ! !end of general form text general_form_address: lname: BLESS fname: ROBERT mi: C. category: PI inst: UNIVERSITY OF WISCONSIN addr_1: DEPT. OF ASTRONOMY city: MADISON state: WI zip: 53706 country: USA phone: 608-262-1715 ! lname: ELLIOT fname: JAMES mi: L. category: CON inst: MASSACHUSETTS INSTITUTE OF TECHNOLOGY addr_1: BLDG. 54-422 city: CAMBRIDGE state: MA zip: 02139 country: USA phone: 617-253-6308 telex: 921473 MIT CAM ! ! end of general_form_address records fixed_targets: targnum: 10 name_1: GSC5800-00460 descr_1: STAR TO BE OCCULTED BY SATURN. descr_2: CLOSE APPROACH AT 12-OCT-93:07:39 pos_1: PLATE-ID = 00WO, pos_2: RA = 21H 47M 02.947S +/- 0.01", pos_3: DEC = -14D 58' 58.18" +/- 0.03", equinox: J2000 acqpr_1: BKG comment_1: SOLAR ELONG 125D fluxnum_1: 1 fluxval_1: B = 12.5 +/- 0.5 ! targnum: 11 name_1: 00460-OFFSET name_2: STAR-2147-1500 descr_1: OFFSET TARGET FOR GSC5800-00460 pos_1: RA = 21H 47M 05.430S +/- 0.04", pos_2: DEC = -14D 59' 53.23" +/- 0.04", equinox: J2000 fluxnum_1: 1 fluxval_1: B = 17.0 +/- 0.2 ! ! end of fixed targets solar_system_targets: targnum: 14 name_1: 00460-BACKGROUND descr_1: OFFSET SATURN lev1_1: STD = SATURN lev2_1: TYPE = POS_ANGLE, lev2_2: RAD = 19.67, lev2_3: ANG = 78.5, lev2_4: REF = NORTH comment_1: FOR USE IN A SCAN OF comment_2: BACKGROUND LEVELS ALONG comment_3: THE PATH OF THE OCCULTED STAR ! ! end of solar system targets ! No generic target records found exposure_logsheet: linenum: 4.000 sequence_1: DEFINE sequence_2: ONBRD-ACQ targname: # config: HSP/VIS opmode: ACQ num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 ! linenum: 6.000 sequence_1: DEFINE sequence_2: BACK-SCAN targname: # config: HSP/PMT/VIS opmode: SPLIT aperture: 1.0 sp_element: F750W/F320N num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: # req_1: SPATIAL SCAN; ! linenum: 7.000 sequence_1: DEFINE sequence_2: RING-OCC targname: # config: HSP/PMT/VIS opmode: SPLIT aperture: 1.0 sp_element: F750W/F320N num_exp: 1 time_per_exp: 1M fluxnum_1: 1 priority: 1 param_1: # ! linenum: 7.500 sequence_1: DEFINE sequence_2: RING-OCC targname: ^ config: S/C opmode: DATA aperture: NONE num_exp: 1 time_per_exp: ^ priority: 1 param_1: FORMAT=FN, req_1: PAR WITH 7.0; comment_1: CAPTURE FGS TLM DURING OCCULTATION. ! linenum: 10.010 sequence_1: USE sequence_2: BACK-SCAN targname: 00460-BACKGROUND time_per_exp: X454 param_1: SAMPLE-TIME = 0.01, param_2: DATA-FORMAT = ALL, param_3: PMT-ANALOG = 1000, param_4: VIS-ANALOG = 100, req_1: SEQ 10.01 - 10.07; req_2: GROUP 10.01 - 10.09 WITHIN 9H; req_3: CYCLE 2/10.01 - 10.32; ! linenum: 10.030 sequence_1: USE sequence_2: BACK-SCAN targname: 00460-BACKGROUND time_per_exp: X454 param_1: SAMPLE-TIME = 0.01, param_2: DATA-FORMAT = ALL, param_3: PMT-ANALOG = 1000, param_4: VIS-ANALOG = 100, ! linenum: 10.070 sequence_1: USE sequence_2: BACK-SCAN targname: 00460-BACKGROUND time_per_exp: X454 param_1: SAMPLE-TIME = 0.01, param_2: DATA-FORMAT = ALL, param_3: PMT-ANALOG = 1000, param_4: VIS-ANALOG = 100, ! linenum: 10.090 sequence_1: USE sequence_2: ONBRD-ACQ targname: 00460-OFFSET time_per_exp: X240 req_1: ONBOARD ACQ FOR 10.10; req_2: SEQ 10.09 - 10.10 NO GAP; req_3: PCS MODE F / 10.09 - 10.10; comment_1: USE FINE LOCK ONLY. IF comment_2: BRIGHT ENOUGH GUIDE STARS comment_3: CANNOT BE FOUND, CANCEL comment_4: OBSERVATION. ! linenum: 10.100 sequence_1: USE sequence_2: RING-OCC targname: GSC5800-00460 time_per_exp: X110 param_1: SAMPLE-TIME = 0.01, param_2: DATA-FORMAT = ALL, param_3: PMT-ANALOG = 1000, param_4: VIS-ANALOG = 100, req_1: AT 12-OCT-93:09:31 +/- 1M; req_2: CRIT OBS; comment_1: END EXPOSURE AT 12-OCT-93:11:20. ! linenum: 10.260 sequence_1: USE sequence_2: BACK-SCAN targname: 00460-BACKGROUND time_per_exp: X454 param_1: SAMPLE-TIME = 0.01, param_2: DATA-FORMAT = ALL, param_3: PMT-ANALOG = 1000, param_4: VIS-ANALOG = 100, req_1: SEQ 10.26 - 10.32; req_2: GROUP 10.10 - 10.32 WITHIN 9H; ! linenum: 10.280 sequence_1: USE sequence_2: BACK-SCAN targname: 00460-BACKGROUND time_per_exp: X454 param_1: SAMPLE-TIME = 0.01, param_2: DATA-FORMAT = ALL, param_3: PMT-ANALOG = 1000, param_4: VIS-ANALOG = 100, ! linenum: 10.320 sequence_1: USE sequence_2: BACK-SCAN targname: 00460-BACKGROUND time_per_exp: X454 param_1: SAMPLE-TIME = 0.01, param_2: DATA-FORMAT = ALL, param_3: PMT-ANALOG = 1000, param_4: VIS-ANALOG = 100, ! ! end of exposure logsheet scan_data: line_list: 10.01, 10.07, 10.26, 10.32 fgs_scan: cont_dwell: C dwell_pnts: 0 dwell_secs: 0.00 scan_width: 0.0000 scan_length: 34.0000 sides_angle: 90.0000 number_lines: 1 scan_rate: 0.0750 first_line_pa: 253.3000 scan_frame: CEL len_offset: 0. wid_offset: 0 ! line_list: 10.03, 10.28 fgs_scan: cont_dwell: C dwell_pnts: 0 dwell_secs: 0.00 scan_width: 2.0000 scan_length: 34.0000 sides_angle: 90.0000 number_lines: 5 scan_rate: 0.0750 first_line_pa: 253.3000 scan_frame: CEL len_offset: 0. wid_offset: 1.0 ! ! end of scan data