! File: 1080C.PROP ! Database: PEPDB ! Date: 16-FEB-1994:00:54:04 coverpage: title_1: THE SIZE AND COMPOSITION OF PLANETARY RING PARTICLES 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: 4.07 num_pri: 8 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 acquisition to verify the guide line_9: stars; (ii) a scan of about 50 arc-seconds along the line_10: track that the object will follow relative to the line_11: planet to determine the planetary contribution to line_12: the background; and (iii) a time series run on the line_13: object with whatever filter-aperture conbination (or line_14: the FOS, if that would prove to be the more line_15: appropriate instrument) that is chosen for the line_16: observation. For some occultations to be observed in line_17: the far UV, prior multi-filter photometry of the line_18: object will be necessary in order to determine the line_19: most appropriate filter (and instrument, the HSP or line_20: FOS) to use for the occultation. For now, we shall ! 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 ! 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, an early acquisition to verify the line_2: guide stars and a prior scan over ten arc-seconds is line_3: needed to map the scattered light field (needed for line_4: the data reduction). ! question: 7 section: 1 line_1: Data will be reduced and analyzed at MIT with the line_2: VAX 11-750 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: 20 name_1: AGK+08D1425 name_2: GSC846-01172 descr_1: A,140 pos_1: PLATE-ID = 0258, pos_2: RA = 10H 51M 54.901S +/- 0.08", pos_3: DEC = 8D 26' 5.56" +/- 0.1", equinox: J2000 acqpr_1: BKG comment_1: SOLAR ELONG 54D comment_2: STAR TO BE OCCULTED BY JUPITER comment_3: CLOSE APPROACH AT 8-JUL-92:22:10 fluxnum_1: 1 fluxval_1: V = 9.7 +/- 0.1 fluxnum_2: 2 fluxval_2: B = 10.2 +/- 0.1 fluxnum_3: 3 fluxval_3: R = 9.5 +/- 0.1 fluxnum_4: 4 fluxval_4: I = 9.3 +/- 0.3 ! ! end of fixed targets solar_system_targets: targnum: 10 name_1: AGK+08D1425-BACKGROUND descr_1: OFFSET JUPITER lev1_1: STD = JUPITER lev2_1: TYPE = POS_ANGLE, lev2_2: RAD = 53.1, lev2_3: ANG = 114, 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 ! targnum: 12 name_1: AGK-BKG2 descr_1: OFFSET JUPITER lev1_1: STD = JUPITER, ACQ = 0.1 lev2_1: TYPE=POS_ANGLE, lev2_2: RAD=68.0, lev2_3: ANG=114, 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 fluxnum_1: 1 fluxval_1: SURF(V) = 5.4 +/- 0.5 ! ! end of solar system targets ! No generic target records found exposure_logsheet: linenum: 4.000 sequence_1: DEFINE sequence_2: FOS-ACQ targname: # config: FOS/RD opmode: ACQ/PEAK aperture: 4.3 sp_element: G650L num_exp: 1 time_per_exp: 0.1S priority: 1 req_1: ONBOARD ACQ FOR 4.100; req_2: SPATIAL SCAN; ! linenum: 4.100 sequence_1: DEFINE sequence_2: FOS-ACQ targname: # config: FOS/RD opmode: ACQ/PEAK aperture: 1.0 sp_element: G650L num_exp: 1 time_per_exp: 0.1S priority: 1 req_1: ONBOARD ACQ FOR 4.200; req_2: SPATIAL SCAN; ! linenum: 4.200 sequence_1: DEFINE sequence_2: FOS-ACQ targname: # config: FOS/RD opmode: ACQ/PEAK aperture: 0.5 sp_element: G650L num_exp: 1 time_per_exp: 0.1S priority: 1 param_1: SCAN-STEP=0.35, param_2: SEARCH-SIZE=3 ! linenum: 6.000 sequence_1: DEFINE sequence_2: FOS-SCAN targname: # config: FOS/RD opmode: RAPID aperture: 1.0 sp_element: G650L wavelength: 3750-8715 num_exp: 1 time_per_exp: 1M priority: 1 param_1: READ-TIME=1.0 param_2: SUB-STEP=1 param_3: COMB=NO req_1: SPATIAL SCAN; comment_1: USE FINE LOCK FOR OFFSET TARGET ACQ comment_2: IF BRIGHT ENOUGH GUIDE STARS CAN BE comment_3: FOUND. IF NOT, COARSE TRACK IS comment_4: ACCEPTABLE. ! linenum: 110.040 sequence_1: USE sequence_2: FOS-ACQ targname: AGK+08D1425 time_per_exp: X5 req_1: ONBOARD ACQ FOR 110.09; req_2: SEQ 110.04 - 110.09 NO GAP; req_3: CYCLE 2 / 110.04 - 110.18; ! linenum: 110.090 targname: AGK+08D1425 config: FOS/RD opmode: RAPID aperture: 1.0 sp_element: G650L wavelength: 3750-8715 num_exp: 1 time_per_exp: 34M fluxnum_1: 1 priority: 1 param_1: READ-TIME=1.0 param_2: SUB-STEP=1 param_3: COMB=NO req_1: CRIT OBS; req_2: PCS MODE F; req_3: AT 8-JUL-92:20:51 +/- 1M; req_4: SEQ 110.09 - 110.18 NO GAP; comment_1: USE FINE LOCK FOR OFFSET TARGET ACQ comment_2: IF BRIGHT ENOUGH GUIDE STARS CAN BE comment_3: FOUND. IF NOT, COARSE TRACK IS comment_4: ACCEPTABLE. ! linenum: 110.100 targname: AGK+08D1425 config: FOS/RD opmode: RAPID aperture: 1.0 sp_element: G650L wavelength: 3750-8715 num_exp: 1 time_per_exp: 38M fluxnum_1: 1 priority: 1 param_1: READ-TIME=1.0 param_2: SUB-STEP=1 param_3: COMB=NO req_1: CRIT OBS; req_2: PCS MODE F; comment_1: END EXPOSURE AT 8-JUL-92:23:30 ! linenum: 110.160 sequence_1: USE sequence_2: FOS-SCAN targname: AGK+08D1425-BACKGROUND time_per_exp: X13 req_1: SEQ 110.16 - 110.18; req_2: GROUP 110.09 - 110.18 WITHIN 9H; ! linenum: 110.170 sequence_1: USE sequence_2: FOS-SCAN targname: AGK-BKG2 time_per_exp: X13 ! linenum: 110.180 sequence_1: USE sequence_2: FOS-SCAN targname: AGK-BKG2 time_per_exp: X13 ! ! end of exposure logsheet scan_data: line_list: 4.00 fgs_scan: cont_dwell: D dwell_pnts: 3 dwell_secs: 1.00 scan_width: 0.0000 scan_length: 2.8000 sides_angle: 90.0000 number_lines: 1 scan_rate: 0.0000 first_line_pa: 0.0000 scan_frame: S/C len_offset: 1.4 wid_offset: 0.00 ! line_list: 4.1 fgs_scan: cont_dwell: D dwell_pnts: 6 dwell_secs: 1.00 scan_width: 0.7000 scan_length: 3.5000 sides_angle: 90.0000 number_lines: 2 scan_rate: 0.0000 first_line_pa: 90.0000 scan_frame: S/C len_offset: 1.75 wid_offset: 0.35 ! line_list: 110.16 fgs_scan: cont_dwell: C dwell_pnts: 0 dwell_secs: 0.00 scan_width: 0.0000 scan_length: 84.2000 sides_angle: 90.0000 number_lines: 1 scan_rate: 0.0750 first_line_pa: 293.0000 scan_frame: CEL len_offset: 0. wid_offset: 0. ! line_list: 110.17 fgs_scan: cont_dwell: C dwell_pnts: 0 dwell_secs: 0.00 scan_width: 3.0000 scan_length: 69.1000 sides_angle: 90.0000 number_lines: 5 scan_rate: 0.0750 first_line_pa: 293.0000 scan_frame: CEL len_offset: 0. wid_offset: 1.5 ! line_list: 110.18 fgs_scan: cont_dwell: C dwell_pnts: 0 dwell_secs: 0.00 scan_width: 0.0000 scan_length: 69.1000 sides_angle: 90.0000 number_lines: 1 scan_rate: 0.0750 first_line_pa: 293.0000 scan_frame: CEL len_offset: 0 wid_offset: 0 ! ! end of scan data