! $Id: 5489,v 4.1 1994/07/27 18:34:47 pepsa Exp $ coverpage: title_1: MULTI-SPECTRAL IMAGES OF VESTA: title_2: CYCLE 4 MEDIUM sci_cat: SOLAR SYSTEM sci_subcat: MINOR PLANETS proposal_for: GO pi_fname: BENJAMIN pi_mi: H. pi_lname: ZELLNER pi_inst: COMPUTER SCIENCES CORPORATION pi_country: USA pi_phone: 410-338-4729 num_pri: 1 wf_pc: Y time_crit: Y ! end of coverpage abstract: line_1: Asteroid 4 Vesta is one of two solar system bodies beyond the line_2: terrestrial planets known to have a highly variegated surface line_3: resulting from surface lava flows. Unlike Io, Vesta's surface line_4: remains insufficiently resolved for the purpose of geologic mapping. line_5: We propose to use the Planetary Camera of the WFPC2 for global imaging line_6: of asteroid 4 Vesta in late 1994. At that geocentric distance, line_7: we expect to resolve more than 140 pixels covering 96% of Vesta's line_8: surface. Images during eight HST orbits are requested for good line_9: spatial coverage of the rotating planet. Four filter passbands line_10: ranging from 0.44 to 1.04 microns wavelength are chosen to provide line_11: mineralogical diagnosticity and to maximize the expected albedo line_12: contrast. Interpretative techniques are described which will lead line_13: to recognition and mapping of pyroxene/feldspar domains indicative line_14: of surface lava flows and olivine-rich regions exposed by impact line_15: of geologic units originally below Vesta's basaltic crust. Also we line_16: anticipate that this program will greatly enhance the interpretability line_17: of a small number of monochromatic images of Vesta to be obtained line_18: at the highest possible pixel resolution by the FOC GTO team. ! ! end of abstract general_form_proposers: lname: ZELLNER fname: BENJAMIN mi: H. inst: 1780 country: USA ! lname: WELLS fname: EDDIE mi: N. inst: 1780 country: USA ! lname: STORRS fname: ALEX inst: 3470 country: USA ! lname: BINZEL fname: RICHARD mi: P. inst: 2630 country: USA ! lname: GAFFEY fname: MICHAEL inst: 3220 country: USA ! lname: ALBRECHT fname: RUDOLPH inst: 5555 country: GERMANY esa: Y ! lname: THOMAS fname: PETER inst: 1810 country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: We want to image asteroid 4 Vesta with the Planetary Camera of the line_2: WFPC2 near its December 1994 opposition. We would prefer that line_3: the solar phase angle be less than 12 degrees (15 degrees OK) line_4: but larger than 2 degrees. line_6: We are using a standard sequence of 7 short exposures in four line_7: filters that should be made contiguously and in a single orbit line_8: of HST. Note Science Tape Recorder management may present a line_9: problem; we would be happy to have PC1 only read out, but there line_10: appears to be no way for the GO to specify that. line_12: We want the sequence to be run 8 times, to map Vesta at about line_13: 45-degree intervals in the longitude of its central meridian. line_14: (Its rotation period is 5.34213 hours.) The eight longitudes line_15: can be be imaged in any order, but should all be done within line_16: a two-week period to minimize aspect changes. It would be most line_17: efficient (but not necessary) for all the observations to be line_18: taken in eight consecutive orbits of HST. line_20: We request fine lock with a guiding tolerance of 0.02 arcsec line_21: during the longest (20 seconds) exposures. Actually gyro line_22: tracking might suffice and can be discussed if necessary. ! question: 4 section: 1 line_1: Groundbased speckle imaging of Vesta has succeeded only in line_2: showing large but poorly defined regions of differing albedo. line_3: Imaging with sufficient resolution for geological interpretations line_4: in mineralogically diagnostic wavelength bands can only be line_5: done with HST or rendezvous spacecraft. ! question: 5 section: 1 line_1: As noted above we want to get Vesta between 2 and 12 degrees line_2: solar phase angle, and at eight different rotational aspects, line_3: more or less equally spaced in longitude. We have used the line_4: PHASE requirement in the exposure logsheet, but the same line_5: results could be accomplished in other ways. ! question: 6 section: 1 line_1: No special calibrations are required. ! ! question: 8 section: 1 line_1: None. ! question: 9 section: 1 line_1: See Phase 1 proposal. ! question: 10 section: 1 line_1: See Phase 1 proposal. ! !end of general form text general_form_address: lname: ZELLNER fname: BENJAMIN mi: H. category: PI inst: 1780 phone: 410-338-4729 telex: zellner@stsci.edu ! lname: category: CON ! ! end of general_form_address records ! No fixed target records found solar_system_targets: targnum: 1 name_1: VESTA descr_1: ASTEROID 4 lev1_1: STD = 4(VESTA) wind_1: SEP OF SUN EARTH FROM VESTA GT 2 D wind_2: SEP OF SUN EARTH FROM VESTA LT 12 D comment_1: ASTEROID 4 VESTA, SOLAR PHASE comment_2: ANGLE > 2 DEG BUT < 12 DEGREES. comment_3: OPPOSITION IS 26 DEC 1994. fluxnum_1: 1 fluxval_1: V = 6.9 +/- 0.2 fluxnum_2: 2 fluxval_2: SIZE = 0.43 +/- 0.02 ! ! end of solar system targets ! No generic target records found exposure_logsheet: linenum: 1.000 sequence_1: DEFINE sequence_2: VESTA-SEQ targname: VESTA config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F673N wavelength: 6732 num_exp: 1 time_per_exp: 2.0 S s_to_n: 100 s_to_n_time: 2.0 S fluxnum_1: 1 priority: 1 req_1: CYCLE 4; req_2: SEQ 1-7 NON-INT; req_3: PCS MODE F / 1-7; req_4: PERIOD 5.34213H +/- 0.00001H; req_5: ZERO-PHASE 25-DEC-1994 +/- 0D comment_1: FIRST OF SEVEN EXPOSURES TO comment_2: BE MADE IN ONE ORBIT; REPEAT 8 comment_3: TIMES TO GET COMPLETE LONGITUDE comment_4: COVERAGE OF ROTATING ASTEROID. comment_5: ZERO-PHASE EPOCH IS ARBITRARY. ! linenum: 2.000 sequence_1: DEFINE sequence_2: VESTA-SEQ targname: VESTA config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F953N wavelength: 9534 num_exp: 1 time_per_exp: 20.0 S s_to_n: 100 s_to_n_time: 20.0 S fluxnum_1: 1 priority: 1 req_1: CYCLE 4; comment_1: SECOND OF SEVEN EXPOSURES TO comment_2: BE MADE IN ONE ORBIT; REPEAT 8 comment_3: TIMES TO GET COMPLETE LONGITUDE comment_4: COVERAGE OF ROTATING ASTEROID ! linenum: 3.000 sequence_1: DEFINE sequence_2: VESTA-SEQ targname: VESTA config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F1042M wavelength: 10201 num_exp: 1 time_per_exp: 10.0 S s_to_n: 100 s_to_n_time: 10.0 S fluxnum_1: 1 priority: 1 req_1: CYCLE 4; comment_1: THIRD OF SEVEN EXPOSURES TO comment_2: BE MADE IN ONE ORBIT; REPEAT 8 comment_3: TIMES TO GET COMPLETE LONGITUDE comment_4: COVERAGE OF ROTATING ASTEROID ! linenum: 4.000 sequence_1: DEFINE sequence_2: VESTA-SEQ targname: VESTA config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F673N wavelength: 6732 num_exp: 1 time_per_exp: 2.0 S s_to_n: 100 s_to_n_time: 2.0 S fluxnum_1: 1 priority: 1 req_1: CYCLE 4; comment_1: FOURTH OF SEVEN EXPOSURES TO comment_2: BE MADE IN ONE ORBIT; REPEAT 8 comment_3: TIMES TO GET COMPLETE LONGITUDE comment_4: COVERAGE OF ROTATING ASTEROID ! linenum: 5.000 sequence_1: DEFINE sequence_2: VESTA-SEQ targname: VESTA config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F953N wavelength: 9534 num_exp: 1 time_per_exp: 20.0 S s_to_n: 100 s_to_n_time: 20.0 S fluxnum_1: 1 priority: 1 req_1: CYCLE 4; comment_1: FIFTH OF SEVEN EXPOSURES TO comment_2: BE MADE IN ONE ORBIT; REPEAT 8 comment_3: TIMES TO GET COMPLETE LONGITUDE comment_4: COVERAGE OF ROTATING ASTEROID ! linenum: 6.000 sequence_1: DEFINE sequence_2: VESTA-SEQ targname: VESTA config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F439W wavelength: 4300 num_exp: 1 time_per_exp: 1.0 S s_to_n: 100 s_to_n_time: 1.0 S fluxnum_1: 1 priority: 1 req_1: CYCLE 4; comment_1: SIXTH OF SEVEN EXPOSURES TO comment_2: BE MADE IN ONE ORBIT; REPEAT 8 comment_3: TIMES TO GET COMPLETE LONGITUDE comment_4: COVERAGE OF ROTATING ASTEROID ! linenum: 7.000 sequence_1: DEFINE sequence_2: VESTA-SEQ targname: VESTA config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F673N wavelength: 6732 num_exp: 1 time_per_exp: 2.0 S s_to_n: 100 s_to_n_time: 2.0 S fluxnum_1: 1 priority: 1 req_1: CYCLE 4; comment_1: SEVENTH OF SEVEN EXPOSURES TO comment_2: BE MADE IN ONE ORBIT; REPEAT 8 comment_3: TIMES TO GET COMPLETE LONGITUDE comment_4: COVERAGE OF ROTATING ASTEROID ! linenum: 101.000 sequence_1: USE sequence_2: VESTA-SEQ req_1: PHASE 0.00 +/- 0.04 OF REF 1.0; req_2: GROUP 101-108 WITHIN 14D comment_1: SINGLE-CCD (PC1) READOUT OK. ! linenum: 102.000 sequence_1: USE sequence_2: VESTA-SEQ req_1: PHASE 0.125 +/- 0.04 OF REF 1.0 comment_1: SINGLE-CCD (PC1) READOUT OK. ! linenum: 103.000 sequence_1: USE sequence_2: VESTA-SEQ req_1: PHASE 0.250 +/- 0.04 OF REF 1.0 comment_1: SINGLE-CCD (PC1) READOUT OK. ! linenum: 104.000 sequence_1: USE sequence_2: VESTA-SEQ req_1: PHASE 0.375 +/- 0.04 OF REF 1.0 comment_1: SINGLE-CCD (PC1) READOUT OK. ! linenum: 105.000 sequence_1: USE sequence_2: VESTA-SEQ req_1: PHASE 0.500 +/- 0.04 OF REF 1.0 comment_1: SINGLE-CCD (PC1) READOUT OK. ! linenum: 106.000 sequence_1: USE sequence_2: VESTA-SEQ req_1: PHASE 0.625 +/- 0.04 OF REF 1.0 comment_1: SINGLE-CCD (PC1) READOUT OK. ! linenum: 107.000 sequence_1: USE sequence_2: VESTA-SEQ req_1: PHASE 0.750 +/- 0.04 OF REF 1.0 comment_1: SINGLE-CCD (PC1) READOUT OK. ! linenum: 108.000 sequence_1: USE sequence_2: VESTA-SEQ req_1: PHASE 0.875 +/- 0.04 OF REF 1.0 comment_1: SINGLE-CCD (PC1) READOUT OK. ! ! end of exposure logsheet ! No scan data records found