! $Id: 5330,v 5.1 1994/07/27 16:38:32 pepsa Exp $ coverpage: title_1: HIGH RESOLUTION MAPPING OF PLUTO'S ALBEDO DISTRIBUTION sci_cat: SOLAR SYSTEM sci_subcat: SATELLITES proposal_for: GO pi_fname: ALAN pi_lname: STERN pi_inst: SOUTHWEST RESEARCH INSTITUTE pi_country: USA pi_phone: [210]-522-5127 hours_pri: 5.87 num_pri: 1 foc: Y off_fname: ROBERT off_lname: CHATTEN off_title: DIRECTOR, CONTRACTS off_inst: 3440 off_addr_1: SOUTHWEST RESEARCH INTSTITUE off_addr_2: 6220 CULEBRA ROAD off_city: SAN ANTONIO off_state: TX off_zip: 78238 off_country: USA off_phone: [210]-522-2235 ! end of coverpage abstract: line_1: This proposal requests time to map Pluto's albedo distribution, line_2: using the highest possible resolution of the CYCLE 4 HST. Maps will line_3: be made in several key UV and visible bandpasses. Our scientific line_4: objectives are to (a) study the distribution of light and dark areas, line_5: (b) make the first disk-resolved estimates of Pluto's limb darkening, line_6: and (c) compositional discriminate pure from contaminated frost line_7: regions. These objectives have not been previously achievable, line_8: but are essential to understanding the surface morphology, line_9: volatile transport, and the root cause of Pluto's secular lightcurve line_10: variations. It may also be possible to detect evidence of the reported line_11: limb haze layer(s) in Pluto's atmosphere. These maps will also provide line_12: the first direct check on Pluto maps made through indirect techniques. line_13: Owing to Pluto's elliptic orbit, we expect the distribution of albedo line_14: to change (on a years-to-decade timescale) as Pluto draws away from line_15: perihelion and volatile transport proceeds. The proposed observations line_16: will document the albedo state at three rotational epochs near the line_17: time of perihelion. These maps will be obtained in two colors, by line_18: the FOC. No other astronomical instrument has sufficient resolution line_19: to accomplish these important scientific objectives. ! ! end of abstract general_form_proposers: lname: STERN fname: ALAN inst: 3440 country: USA ! lname: TRAFTON fname: LARRY mi: M. inst: 3550 country: USA ! lname: BUIE fname: MARC inst: 2540 country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: We are proposing to obtain FOC images of Pluto using the f/96 chain with line_2: two filter combinations: F278M+F275W, and F410M. The FOC obtains its maximum line_3: spatial resolution near 3000 \AA; this resolution of 0.020-0.034 arcsec line_4: (Paresce, personal communication) is the best obtainable on HST. line_6: To isolate UV light with the F278M bandpass, we will simultaneously employ line_7: F275W to supress red leaks. For both the UV F278M+F275W and blue F410M image line_8: configurations, neutral density filters are required to supress $N_{max}$ line_9: and thus operate the FOC detectors in the linear regime. Each image will be line_10: exposed to obtain a S/N of 20-25 per resolution element. This will permit line_11: the detection of 10\% pixel-to-pixel relative albedo contrasts with line_12: confidence. line_14: Four sets of images are requested. Each set will consist of a UV and a BLUE line_15: image. These image sets will be spaced about eqaully in rotational phase line_16: (Pluto rotates in 6.4 days). line_19: For all of the observations, the 512x512 aperture will be combined with an line_20: FOC IMAGE mode with 0.014 arcsec pixels, to give a field of view (FOV) of line_21: 7x7 arcsec across. This FOV is large compared to both Pluto's diameter line_22: and the Pluto-Charon separation, which never exceeds 0.9 arcsec. ! question: 3 section: 2 line_1: We will acquire Pluto in the FOC FOV using blind pointing, which the Cycle 4 line_2: FOC Handbook describes as the standard acquisition mode for all imaging line_3: observations with a FOV >3 arcsec. During exposures, HST will be held in line_4: Fine Lock mode. Fine Lock provides a pointing stability of 0.005 line_5: arcsec, which is several times smaller than the optical resolution. line_7: The F410M filter will map Pluto at a wavelength where a considerable amount line_8: of photometric lighcurves have been made. line_10: We calculated our exposure times assuming Pluto's radius is 1180 km, Pluto line_11: is 30 AU from both the Earth and the Sun, its visible geometric albedo is 0.55 line_12: (Binzel 1988), and its UV geometric albedo is 0.38 (derived from IUE line_13: low-resolution UV reflectance spectra; Stern et al. 1991). Assuming a line_14: background level of $1x10^{-4}$ counts/sec/pixel, and a resolution element line_15: size of 0.025 arcsec, FOC f/96 images with S/N of 20 or greater should be line_16: obtainable in 44 min at a count rate of 0.14 Hz. This is far below the FOC line_17: $N_{max}$ constraint of 0.6 Hz set by the selected IMAGE observing mode. line_19: Using a target count rate of 0.15 Hz, and the FOC prescription for line_20: count rate estimates given on page 78 of the Cycle 4 FOC Handbook, line_21: we reach the following conclusions: 1) for F410M images, the F4ND filter is line_22: required; for the F278M+F275W images, the F2ND filter is required. ! question: 4 section: 1 line_1: The studies we are proposing rely on UV techniques and spatial resolutions line_2: which only HST can accomplish. Pluto's 0.1 arc-sec diameter is simply too small line_3: to be directly imaged from beneath the terrestrial atmosphere. line_5: No other spacecraft can obtain the resolution or UV performance line_6: required by the scientific objectives of this program. Although a NASA line_7: mission may well be sent to reconnoiter Pluto, the earliest feasible arrival line_8: date is over 11 years hence. ! question: 5 section: 1 line_1: No real-time observations or special calibrations are required. line_3: To achieve the desired goals, each of the 4 requested rotational epochs line_4: must be achieved to within 2% rotational phase (+/- 7 deg). This line_5: corresponds to a 17 hour window centered on each rotational phase. line_6: These observations may be obtained on any apparition of line_7: the specified rotational phases in the Cycle. ! question: 6 section: 1 line_1: None. ! ! ! question: 8 section: 1 line_1: None. ! question: 9 section: 1 line_1: PI Stern: P4024 High Resolution UV Spectroscopy of Triton (as PI); line_2: P2560 UV Rotational Light Curves of Pluto, and Charon's UV Spectrum (as line_3: CoI); P3803 CO Abundance and FUV Survey (as CoI); P4005 Observations of line_4: Jovian Aurora in Support of Ulysses (as PI); P4462 Deep UV Spectroscopy of line_5: Triton (as CoI). line_7: CoI Trafto8: P1202 Lyman-alpha and H2 Survey; P1203 Jovian Auroral line_9: Ly-alpha Profile (as PI); P1204 Io Proton Aurora (as PI); 1206 Sulfur Near line_10: Io (as PI); P1290 Uranus and Neptune below 3000 A (as PI); 2569 UV line_11: Rotational Light Curves for Pluto, & Charon's UV Spectrum (as PI); P2957 line_12: High Resolution UV Spectroscopy of Triton (as CoI); P2560 Integrated line_13: Dynamical and Spectroscopic Observations of Jupiter and Saturn (as CoI); line_14: P3803 Pluto's FUV Spectrum: CO Abundance and FUV Survey (as PI); P4001 H2 line_15: Survey of Jupiter's Northern Aurora During Ulysses Flyby (as PI); P4005 HST line_16: UV Imaging of Jupiter to Support the Interpretation of Ulysses X-ray line_17: Measurements (as CoI). line_19: Buie: Separate Lightcurves of Pluto and Charon; P3848 (as PI). The line_20: Structure of the Inner Coma of Comet Chiron; P3769 (as CoI). ! question: 10 section: 1 line_1: Our proposal team has experience with IUE and HST ultraviolet spectroscopy line_2: (Stern & Trafton) and HST visible photometry (Buie) of Pluto. All three line_3: investigators are well-recognized experts on Pluto. CoI Buie has led one of line_4: the two primary groundbased mapping groups. PI Stern and CoI Trafton have line_5: been involved in atmospheric and volatile transport work for over a decade. line_7: Southwest Research Institute will support this project by providing all line_8: required computing facilities for the PI, and by foregoing overhead on PI line_9: travel and the salary of any postdoc involved in data analysis. The line_10: individual CoI institutions (U.~Texas and Lowell Observatory) will provide line_11: existing workstations for each CoI. A pool of astronomy graduate students is line_12: available at The University of Texas to draw research assistants. ! !end of general form text general_form_address: lname: STERN fname: ALAN category: PI inst: 3440 addr_1: SPACE SCIENCE DEPARTMENT addr_2: SOUTHWEST RESEARCH INSTITUTE addr_3: 6220 CULEBRA ROAD city: SAN ANTONIO state: TX zip: 78238 country: USA phone: [210]522-5127 telex: ALAN@SWRI.SPACE.SWRI.EDU ! lname: category: CON ! ! end of general_form_address records ! No fixed target records found solar_system_targets: targnum: 1 name_1: PLUTO descr_1: PLANET PLUTO lev1_1: STD=PLUTO, ACQ = 0.01 lev2_1: STD=PLUTO lev3_1: STD=PLUTO comment_1: OUR TARGET IS PLUTO. ITS SATELLITE comment_2: CHARON WILL BE IN THE FIELD. comment_3: ACQ=0.01 TO ENSURE FINE LOCK, PER comment_4: ALEX STORRES SUGGESTION. fluxnum_1: 01 fluxval_1: V=13.7 fluxnum_2: 02 fluxval_2: B-V=0.72 ! ! end of solar system targets ! No generic target records found exposure_logsheet: linenum: 1.000 targname: PLUTO config: FOC/96 opmode: IMAGE aperture: 512X512 sp_element: F278M,F275W,F1ND num_exp: 001 time_per_exp: 37M s_to_n: 55 s_to_n_time: 34M fluxnum_1: 001 priority: 01 req_1: CYCLE 4; req_2: PCS MODE F; req_3: SAME ORIENT FOR 1 AS 2; req_4: GROUP 1-2 NO GAP; req_5: REPEAT 1-2 EVERY 38H +/- 3H req_6: FOR 3 MORE TIMES; req_7: AT 15-MAY-94 +/- 85D; req_8: SAME POS FOR 1 AS 2; comment_1: 1) BLIND ACQ; FINE LOCK. 2) EXPOSE comment_2: 2) EXPOSE F275W+F278M+F1ND; comment_3: 3) THEN F410M+F4ND WITH SAME ORIENT. comment_4: REPEAT 3 TIMES AS PLUTO ROTATES (EVERY comment_5: 38+/-3H). GUIDE=FINE MODE. EXPOSE <65D comment_6: FROM OPPOSITION TO MINIMIZE PLUTO DIST ! linenum: 2.000 targname: PLUTO config: FOC/96 opmode: IMAGE aperture: 512X512 sp_element: F410M,F4ND num_exp: 001 time_per_exp: 44M s_to_n: 20 s_to_n_time: 44M fluxnum_1: 001 priority: 01 req_1: CYCLE 4; req_2: PCS MODE F; comment_1: 1) BLIND ACQ; FINE LOCK. comment_2: 2) EXPOSE F275W+F278M+F1ND; comment_3: 3) THEN F410M+F4ND WITH SAME ORIENT. comment_4: REPEAT 3 TIMES AS PLUTO ROTATES (EVERY comment_5: 38+/-3H). GUIDE=FINE MODE. EXPOSE <65D comment_6: FROM OPPOSITION TO MINIMIZE PLUTO DIST ! ! end of exposure logsheet ! No scan data records found