! File: 4545C.PROP ! Database: PEPDB ! Date: 22-FEB-1994:17:03:27 coverpage: title_1: OUTGASSING FROM CERES -- CYCLE 3 HIGH sci_cat: SOLAR SYSTEM sci_subcat: MINOR PLANETS proposal_for: GO pi_fname: MICHAEL pi_mi: F. pi_lname: A'HEARN pi_inst: UNIVERSITY OF MARYLAND pi_country: USA hours_pri: 4.07 num_pri: 1 fos: Y time_crit: Y funds_length: 12 off_fname: VICTOR off_mi: E. off_lname: MEDINA off_title: DIRECTOR, ORAA off_inst: 2620 off_addr_1: OFFICE OF RESEARCH ADMINISTRATION AND ADVANCEMENT off_addr_2: UNIVERSITY OF MARYLAND off_city: COLLEGE PARK off_state: MD off_zip: 207422421 off_country: USA off_phone: 301-405-6269 ! end of coverpage abstract: line_1: We propose to search for outgassing from Ceres by searching for line_2: emission by OH as recently reported by A'Hearn and Feldman using data line_3: data taken with IUE (1992 Icarus 98,54-60). If this emission can be line_4: confirmed with the higher sensitivity of HST, our picture of Ceres line_5: will have to be fundamentally changed. ! ! end of abstract general_form_proposers: lname: A'HEARN fname: MICHAEL title: PI mi: F. inst: UNIVERSITY OF MARYLAND country: USA ! lname: FELDMAN fname: PAUL mi: D. inst: JOHNS HOPKINS UNIVERSITY country: USA ! lname: MCFADDEN fname: LUCY mi: A. inst: UNIVERSITY OF MARYLAND country: USA ! lname: WEAVER fname: HAROLD mi: A. inst: STSCI country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: We will use FOS red side with grating G270H. We will use the line_2: 4.3 arcsec aperture to maximize signal. This will yield a line_3: resolution of 1.4 arcsec perpendicular to the dispersion before line_4: convolution with the PSF, significantly higher than available with line_5: IUE which has a PSF of at least 3 arcsec and for which we must line_6: integrate a slit length of at least 10 arcsec in order to obtain line_7: a significant detection. We propose to observe adjacent to two line_8: opposite limbs of Ceres to explore the spatial variability and at line_9: two distances both to explore the radial distribution and to line_10: adequately deal with scattered light from Ceres. We propose to use line_11: the acquisition spectra of Ceres, obtained in the 'Hartig maneuver' line_12: to provide a spectrum of Ceres itself with high S/N and identical line_13: spectral resolution. This will be scaled and fit to the scattered line_14: light in the offset exposures to provide proper subtraction of the line_15: scattered light. In addition, we will use this spectrum to search line_16: for geologically significant spectral features. line_17: At each limb, we will position Ceres just outside the 4.3-arcsec line_18: aperture (top and bottom edges) and obtain spectra through both line_19: the 'top' and 'bottom' 1.4x4.3 strips of the 4.3 arcsec aperture of line_20: FOS. The aperture closer to Ceres will be somewhat contaminated by line_21: light from the PSF of Ceres but will enable us to explore a spatial line_22: region not accessible with IUE. The aperture further from Ceres line_23: will be positioned at the distance at which we previously detected ! question: 3 section: 2 line_1: OH using IUE. The IUE observation was severely contaminated with line_2: scattered light at this larger distance. With HST, the scattered line_3: light should be very small for the more distant position. On one line_4: side of Ceres we will obtain data at 3 radial distances line_5: corresponding to the 3 strips in the 4.3 arcsec aperture in an line_6: to better define the radial profile of OH. ! question: 4 section: 1 line_1: This proposal is for a followup to a dramatic discovery made with line_2: IUE and which requires far higher sensitivity than achievable with line_3: IUE. Further IUE observations are planned but they will only have line_4: sufficient sensitivity if the OH is brighter than for our one line_5: positive detection. Ground-based observations are also planned line_6: (already scheduled with the NTT at ESO) but, due in part to the line_7: huge atmospheric attenuation at these wavelengths, the estimated line_8: limit to our sensitivity is only comparable to that with IUE. ! question: 4 section: 2 line_1: Our recent observations of comet Shoemaker-Levy have shown that we line_2: can reach surface brightnesses of about 4 Rayleighs (S/N~2.5) with line_3: exposure times of order 1/2 hour using the 4.3 arcsec aperture of line_4: FOS. This is consistent with the following calculation: The OH line_5: band, with natural width about 20-25 Angstroms, is convolved with a line_6: rectangular slit of width roughly 25 Angstroms. We assume a line_7: trapezoidal profile with base 50 Angstroms and top 10 Angstroms. A line_8: total brightness of 1 Rayleigh yields a peak count rate at the line_9: center of the band ~0.0023 counts per second per diode whereas the line_10: dark current should be 0.010 counts per sec per diode. If we ignore line_11: the scattered light from Ceres, a surface brightness of 3 Rayleighs line_12: should yield S/N~3 in one hour for the peak pixel. Integration over line_13: a range of wavelenghts will increase the S/N to 10 for the whole line_14: band although this ignores the noise induced by subtracting the line_15: baseline. We should be able to detect a brightness of 1-2 Rayleighs line_16: with a one-hour exposure and resolve the band for a brightness of 3 line_17: Rayleighs. Since Ceres itself is very bright, we propose to obtain line_18: spectra at 2(3) radial distances, the larger of which should be line_19: uncontaminated by scattered light. If we can successfully remove line_20: the scattered light, which will dominate the closer exposure, we may line_21: be able to detect the higher surface brightness that one would line_22: expect to see closer to Ceres. ! question: 5 section: 1 line_1: Since the fluorescence efficiency of OH varies with heliocentric line_2: distance and since the spatial distribution of OH should drop with line_3: distance from Ceres, we need to minimize both geocentric and line_4: heliocentric distances. The geocentric distance is a minimum in line_5: late October 1993 while the heliocentric distance is decreasing line_6: slowly throughout cycle 3. We also require that the offsets be line_7: generally in the direction of the north and south poles of Ceres. line_8: Since the pole of Ceres is certainly generally north-south and, line_9: according to recent measurements by a French group, probably line_10: projected at PA=323 during fall 1993, we are limited to times when line_11: the solar direction is roughly (+/- 30 degrees) orthogonal to this line_12: direction. The combined constraints limit us to a short window in line_13: late summer before opposition and a wider window in late fall after line_14: opposition. All observations must be contiguous in order to line_15: simplify the interpretation. ! question: 7 section: 1 line_1: Preliminary reductions will be carried out at STScI with final line_2: reductions carried out in parallel at JHU and at UMd. Modelling for line_3: a positive detection will be carried out at UMd elaborating on the line_4: very simple exospheric model described by A'Hearn and Feldman. ! question: 8 section: 1 line_1: ! question: 9 section: 1 line_1: P3064:HST Observations of Comet Levy (1990c). No relation. line_2: P2481:HST Observations of Periodic Comets. No relation. line_3: P2442:Cometary Parent Molecules-Target of Opportunity. No relation. line_4: P2483:The Volatile Composition of New Comets-Target of Opportunity. line_5: No relation line_6: P3707:HST Observations of Periodic Comets. No relation. ! question: 9 section: 2 line_1: P3064: We successfully obtained images of comet Levy prior to line_2: implementation of moving target tracking capabilities. We showed line_3: that the photometric variability was correlated with outflow of a line_4: shell of dust at a surprisingly low velocity, of order 0.2 km/s, line_5: thus implying that the particles reflecting the continuum are very line_6: large. We showed that, even at 0.1 arcsec resolution, there were line_7: no jets visible thus showing that the variability is likely to be line_8: due to a quite different source than in the case of comet Halley line_9: where the variability was caused by jets turning on and off. line_10: P2481: We obtained FOS spectra of comet P/Hartley 2. The most line_11: dramatic result was detection of the CO Cameron bands, never before line_12: seen in a comet. These bands are produced when CO2 photodissociates line_13: to form CO in an excited, metastable state. The intensity is line_14: therefore a new tracer of the CO2 abundance, the only tracer line_15: observable from Earth until ISO is launched. line_16: P2442 and 2483: The first data, spectra with HRS and FOS line_17: respectively, were obtained only in the week preceding writing this line_18: proposal. The reductions are not yet complete. line_19: P3707: No data have yet been obtained for this program. ! question: 9 section: 3 line_1: Inner Coma Imaging of Comet Levy (1990c) with the Hubble Space line_2: Telescope. Weaver, H. A., M. F. A'Hearn, P. D. Feldman, C. Arpigny, line_3: W. A. Baum, J. C. Brandt, R. M. Light, and J. A. Westphal (1992). line_4: Icarus, 97, 85-98. (ref:P3064) line_5: The results from P2481 have been presented at meetings and published line_6: as an abstract but a complete paper has not yet been submitted for line_7: publication. line_8: An additional paper discussing models for the data obtained under line_9: P3064 is in manuscript form by Samarasinha et al. but has not yet line_10: been submitted for publication. ! question: 10 section: 1 line_1: The institutions of the investigators will supply all computing line_2: facilities needed for the analysis of the data and for interpretive line_3: modelling. The institutions will also provide the salary costs for line_4: the investigators. All institutions operate networks on which line_5: reduction software, e.g., STSDAS/ IRAF/IDL, is readily available. ! !end of general form text general_form_address: lname: A'Hearn fname: Michael mi: F. category: PI inst: University of Maryland addr_1: Department of Astronomy addr_2: University of Maryland city: College Park state: MD zip: 207422421 country: USA phone: 301-405-6076 ! ! end of general_form_address records ! No fixed target records found solar_system_targets: targnum: 1 name_1: 1-CERES descr_1: ASTEROID 0001 lev1_1: STD = 1(CERES) wind_1: WND1 = 28-AUG-93 TO 10-SEP-93 wind_2: WND2 = 03-NOV-93 TO 22-DEC-93 comment_1: GOAL OF SETTING WINDOW IS TO KEEP comment_2: GOOD SPATIAL RESOLUTION, I.E. TO comment_3: STAY NEAR OPPOSITION, BUT TO ALSO comment_4: FORCE THE +/- Y OFFSETS WITH FOS comment_5: TO BE WITHIN 30 DEGREES OF THE comment_6: PROJECTED ROTATION AXIS OF CERES comment_7: WHICH IS AT TRUE PA = 323 DURING comment_8: THIS PERIOD. THIS ASSUMES THAT comment_9: +/- Y IS PERPENDICULAR TO THE comment_10: SUN-COMET LINE. fluxnum_1: 1 fluxval_1: V = 8.0 +/- .5 ! targnum: 2 name_1: CERES-OFF-1 descr_1: OFFSET CERES lev1_1: STD = 1(CERES), lev1_2: ACQ = 0.3 lev2_1: TYPE = POS_ANGLE, lev2_2: RAD = 3.7, lev2_3: ANG = 90., lev2_4: REF = SUN wind_1: WND1 = 28-AUG-93 TO 10-SEP-93 wind_2: WND2 = 03-NOV-93 TO 22-DEC-93 comment_1: FLUXNUM_1 IS CERES FOR ACQUISITION. comment_2: FLUXNUM_2 IS AT OFFSET FOR SPECTRAL comment_3: EXPOSURE. comment_4: OFFSET IS IN FOS -Y DIRECTION fluxnum_1: 1 fluxval_1: V = 8.0 +/- .5 fluxnum_2: 2 fluxval_2: SURF-LINE(3085) = 4.E-17 fluxnum_3: 3 fluxval_3: W-LINE(3085) = 20. ! targnum: 3 name_1: CERES-OFF-2 descr_1: OFFSET CERES lev1_1: STD = 1(CERES), lev1_2: ACQ = 0.3 lev2_1: TYPE = POS_ANGLE, lev2_2: RAD = 3.7, lev2_3: ANG = 270., lev2_4: REF = SUN wind_1: WND1 = 28-AUG-93 TO 10-SEP-93 wind_2: WND2 = 03-NOV-93 TO 22-DEC-93 comment_1: FLUXNUM_1 IS CERES FOR ACQUISITION. comment_2: FLUXNUM_2 IS AT OFFSET FOR SPECTRAL comment_3: EXPOSURE. comment_4: OFFSET IS IN FOS -Y DIRECTION fluxnum_1: 1 fluxval_1: V = 8.0 +/- .5 fluxnum_2: 2 fluxval_2: SURF-LINE(3085) = 4.E-17 fluxnum_3: 3 fluxval_3: W-LINE(3085) = 20. ! ! end of solar system targets ! No generic target records found exposure_logsheet: linenum: 1.000 targname: 1-CERES config: FOS/RD opmode: IMAGE aperture: 4.3 sp_element: G270H wavelength: 3090 num_exp: 1 time_per_exp: 15M s_to_n: 30 s_to_n_time: 3M fluxnum_1: 1 priority: 1 param_1: Y-SIZE = 5 param_2: Y-SPACE = 128 param_3: COMB = YES param_4: SUB-STEP = 4 req_1: SEQ 1-3 NOGAP; req_2: RT ANALYSIS FOR 2; req_3: CYCLE 3; comment_1: GET FIVE FOS SPECTRA AT comment_2: DIFFERENT Y DEFLECTIONS TO FIND comment_3: POSITION OF CERES. comment_4: THESE SPECTRA WILL ALSO BE USED comment_5: TO FIT SCATTERED LIGHT OF CERES. ! linenum: 2.000 targname: CERES-OFF-1 config: FOS/RD opmode: IMAGE aperture: 4.3 sp_element: G270H wavelength: 3090 num_exp: 8 time_per_exp: 15M s_to_n: 5 s_to_n_time: 1H fluxnum_1: 2 priority: 1 param_1: Y-SIZE = 2 param_2: Y-SPACE = 512 param_3: COMB = YES param_4: SUB-STEP = 4 req_2: CYCLE 3; comment_1: TWO FOS SPECTRA WILL BE OBTAINED comment_2: WITH 1.4X4.3 APER. CENTERED 2.6 comment_3: AND 4.8 ARCSEC FROM CERES. comment_4: ADJUST EXPOSURE TO FILL ORBIT. comment_5: MAY NEED TO SWITCH TO ACCUM MODE comment_6: PENDING INFO FROM FOS SCIENTISTS. ! linenum: 2.900 targname: 1-CERES config: FOS/RD opmode: IMAGE aperture: 4.3 sp_element: G270H wavelength: 3090 num_exp: 1 time_per_exp: 15M s_to_n: 30 s_to_n_time: 3M fluxnum_1: 1 priority: 1 param_1: Y-SIZE = 5 param_2: Y-SPACE = 128 param_3: COMB = YES param_4: SUB-STEP = 4 req_2: RT ANALYSIS FOR 3; req_3: CYCLE 3; comment_1: GET FIVE FOS SPECTRA AT comment_2: DIFFERENT Y DEFLECTIONS TO FIND comment_3: POSITION OF CERES. comment_4: THESE SPECTRA WILL ALSO BE USED comment_5: TO FIT SCATTERED LIGHT OF CERES. ! linenum: 3.000 targname: CERES-OFF-2 config: FOS/RD opmode: IMAGE aperture: 4.3 sp_element: G270H wavelength: 3090 num_exp: 8 time_per_exp: 15M s_to_n: 5 s_to_n_time: 1H fluxnum_1: 2 priority: 1 param_1: Y-SIZE = 2 param_2: Y-SPACE = 512 param_3: COMB = YES param_4: SUB-STEP = 4 req_2: CYCLE 3; comment_1: TWO FOS SPECTRA WILL BE OBTAINED comment_2: WITH 1.4X4.3 APER. CENTERED 2.6, 3.7 comment_3: AND 4.8 ARCSEC FROM CERES. comment_4: ADJUST EXPOSURE TO FILL ORBIT. comment_5: MAY NEED TO SWITCH TO ACCUM MODE comment_6: PENDING INFO FROM FOS SCIENTISTS. ! ! end of exposure logsheet ! No scan data records found