! File: 4662C.PROP ! Database: PEPDB ! Date: 22-FEB-1994:21:37:22 coverpage: title_1: EXPLORING TRITON'S UV SPECTRUM: title_2: THE FIRST 1800-2500 A UV SURVEY-- CYCLE3 HIGH sci_cat: SOLAR SYSTEM sci_subcat: SATELLITES proposal_for: GO pi_fname: S. pi_mi: A. pi_lname: STERN pi_inst: SOUTHWEST RESEARCH INSTITUTE pi_country: USA hours_pri: 8.00 num_pri: 1 fos: Y funds_length: 12 off_fname: ROBERT off_mi: E. off_lname: CHATTEN off_title: DIRECTOR, CONTRACTS off_inst: 3440 off_addr_1: SPACE SCIENCE DEPARTMENT off_addr_2: SOUTHWEST RESEARCH INSTITUTE off_addr_3: 6220 CULEBRA ROAD off_city: SAN ANTONIO off_state: TX off_zip: 78238 off_country: USA off_phone: (210)522-3948 ! end of coverpage abstract: line_1: We propose to make observations of Triton using the FOS/BL with line_2: G190H to survey the 1800-2200 A spectral region, and FOS/BL G270H line_3: to survey the 2200-2500 A region. Neither of these spectral regions line_4: have been observed before. These exposures will exhibit 1.5-2 A line_5: resolution and good S/N. Our objectives are to search for (i) direct line_6: evidence of CO and other O-bearing molecules in Triton's atmosphere, line_7: (ii) evidence of hydrocarbon or nitrile absorptions on Triton's line_8: surface, and (iii) to determine Triton's 1800-2500 A albedo and albedo line_9: slope. These objectives will complete the first-order spectral line_10: characterization of Triton. Only HST has the sensitivity to carry out line_11: these UV studies. As a byproduct of the G270H exposure, the line_12: 2500-3250 A region will also be observed, adding a fifth spectrum to line_13: improve the sparse database on Triton's UV rotational variability. ! ! end of abstract general_form_proposers: lname: STERN fname: S. title: PI mi: A. inst: 3440 country: USA esa: N ! lname: TRAFTON fname: LAURENCE mi: M. inst: 3550 country: USA esa: N ! lname: LUNINE fname: JONATHAN mi: I. inst: 1210 country: USA esa: N ! lname: BURATTI fname: BONNIE mi: J. inst: 2370 country: USA esa: N ! lname: GLADSTONE fname: RANDAL mi: R. inst: 3440 country: USA esa: N ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: We plan to observe Neptune's satellite Triton at a single epoch line_2: in Cycle 3to make FOS/BL spectra with two different gratings: line_3: G190H and G270H. line_5: Our program is is suited to Cycle 3 for several reasons: First, Neptune line_6: and Triton are summer-fall objects, and therefore well-suited to Cycle 3 line_7: observations. Second, we do not require any of the post-repair and reboost line_8: imaging improvements to carry this project out (indeed, we plan to use the line_9: 4.3 arcsec FOS ACQ aperture which admits the entire, aberrated OTA beam). line_10: Finally, the installation of COSTAR will decrease UV through-put by line_11: 1/3, thereby increasing the time-requirement to perform this program line_12: in future cycles. line_14: The G190H observations are our highest priority: they will provide the first line_15: high S/N 1800-2100 A survey spectrum of Triton, and cover a region of prime line_16: interest for CO, NO, and surface contaminant detection. The G270H will line_17: provide a new, rotationally, resolved dimension to augment our Cycle 1 G270H line_18: HST spectra. As in Cycle 1, we plan to employ the ACCUM mode. line_20: We will acquire Triton in the large, 4.3 arcsec square ACQ aperture, as we line_21: did in our successful Cycle 1 effort (P4024). The planned ACQ is BINARY, as line_22: suggested by STScI staff. No BRIGHT or FAINT limits were suggested. Use of the line_23: 4.3 arcsec aperture reduces acquisition time, maximizes signal through-put (our ! question: 3 section: 2 line_1: main objective), and increases program efficiency (i.e., exposure line_2: time/spacecraft time). In this configuration the FOS has good spectral line_3: resolution, and can clearly achieve our objectives. Based on the FOS background line_4: in the Cycle 1 Triton data (and several 14-hour Triton integrations using IUE's line_5: 11x larger LWLA aperture), we are confident that the use of the FOS acquisition line_6: aperture in the Cycle 3 work will not induce any significant background. line_8: The G190H spectra will be integrated for 70 minutes at each rotational epoch line_9: to span the 1800-2310 A region. The G270H spectra will be integrated for 25 line_10: minutes to span the 2220-3278 A region. We prefer these spectra be obtained line_11: consecutively (in either order). A total of 5 such G190H + G270 H observing line_12: sets are planned over a 6 day period to achieve good rotational coverage line_13: over a 5.77 day Triton rotation. The total spacecraft time estimate for this line_14: program is 11.31 hours. line_16: We have requested 5 observations space ~1 day apart. The reason we want to line_17: group the observations in time and not just phase is to get the best possible line_18: data. The time grouping keeps all the observations (i) at essentially the same line_19: solar phase and (ii) minimizes the change in the solar spectrum below 2300 A line_20: due to solar rotation and time variability. Because we are looking for line_21: rotational variations in Triton, the latter is particularly important. ! question: 3 section: 3 line_1: Not aplicable. ! question: 4 section: 1 line_1: This is a proposal to perform UV spectroscopy at wavelengths far below the line_2: atmospheric cutoff. Therefore neither groundbased nor airborne observations line_3: can satisfy our objectives. No accepted GO or GTO program will obtain line_4: spectra of Triton in the critical 1800-2500 A region we are proposing for. line_5: Only the UV offers molecular absorption coefficients large enough to detect line_6: the key O-bearing atmospheric constituents we are searching for. Past UV line_7: work on Triton and Pluto (e.g., Broadfoot, et al. 1989; Stern, et al. 1989, line_8: 1991) has yielded important clues about these bodies. Completing the UV line_9: survey of Triton offers to reveal valuable new information. line_11: As demonstrated by past Triton work (Stern, et al. 1989; Stern, et al. line_12: 1991), IUE does not have the sensitivity to study Triton below 2500 A. line_13: Further, the Voyager UVS had a red-wavelength cutoff of 1800 A (Broadfoot, line_14: et al. 1989), and therefore left unexplored the 1800-2500 A region we want line_15: to study. HST is the only facility capable of completing the Triton UV line_16: survey and making the observations proposed here. ! question: 4 section: 2 line_1: This HST program requests to make new spectra of Triton to achieve sensitive line_2: constraints on the composition and chemistry of Triton's atmosphere, and to line_3: further study Triton's UV reflectance properties as a function of rotational line_4: phase. About 7 hours of exposure time in the 1800-2310 A region will be line_5: obtained with FOS/RD/G190H, at an effective FWHM resolution of 2.18 A. Further, line_6: ~2.5 hours of exposure in the 2220-3278 A region will be obtained using G270H, line_7: at 3.08 A resolution. This is more than 5x the Cycle 1 exposure. line_9: The most challenging part of the proposed experiment involves the search for line_10: the (0-0) CO Cameron band at 2060 A. Based on Triton's UV flux at 2700 A line_11: (Stern, et al. 1989; Stern, et al. 1992) and the declining solar spectrum line_12: (Mount and Rottman 1983), Triton's flux should be 3x10^-17 ergs/cm2/s2/A at line_13: 2060 A. At 2060 A, the FOS Instrument Handbook (V2.0, April 1992) predicts a line_14: FOS/RD+G190H/4.3" acquisition aperture (which has a large throughput factor, line_15: 0.5) count rate of 0.0041 Hz/diode; this compares well to the estimated FOS line_16: dark count rate of 0.0027 Hz/diode. The proposed observations should produce a line_17: S/N of 7-9/diode (1.45 A) on Triton's reflectance spectrum at 2060 A. Since 5-6 line_18: diodes span the 0-0 vibrational band, we expect a band-detection S/N near 20. line_19: This is quite adequate to detect or severely constrain CO in absorption. line_21: For the 1989 A Cameron band, 99 total counts/diode are predicted for a 6.5 hour line_22: exposure, corresponding to a S/N=7/diode, or S/N=16 over the whole band. This line_23: will be useful for confirming the 2060 A (0-0 band) results. ! question: 4 section: 3 line_1: line_2: Similar calculations give S/N estimates of ~12-14/diode around 2200 A, where line_3: the NO and surface contaminant searches will be carried out, and S/N line_4: ~35-40/diode (2.05 A) at 2700 A on Triton's continuum albedo. Clearly HST line_5: is capable of making precise reflectance albedo measurements and searching line_6: for new surface absorption features (cf., Scientific Justification). The line_7: total exposure time requested is 10.0 hours; the total spacecraft time line_8: requirement is 11.31 hours. The program's Phase I Resource Estimator line_9: efficiency is over 70%. ! question: 5 section: 1 line_1: We have no special observing requirements, and can observe line_2: whenever Neptune/Triton is outside the standard HST solar and lunar line_3: avoidance zones. To demonstrate this, we note that our Cycle 1 FOS line_4: observation was made at 11.5 arcsec elongation and showed no evidence of line_5: Neptune-scattered light. In Cycle 1 we observed Triton virtually at its line_6: minimum elongation from Neptune, since the geometry of its orbit as seen line_7: from Earth never allows Triton to appear <11 arcsec from Triton in 1993 line_8: (cf., Astronomical Almanac 1993). line_10: No real-time observations are required. ! question: 6 section: 1 line_1: None. ! question: 7 section: 1 line_1: The PI and CoI Trafton have experience with the HST FOS and GHRS instruments line_2: from Cycles 1 and 2. The PI is also experienced with IUE spectroscopy of icy line_3: satellites, Pluto, and asteroids. Our team has considerable experience with line_4: groundbased observations of planets and icy satellites from major line_5: observatories. line_7: The FOS data will be reduced at STScI using custom processing with line_8: STSDAS. The FOS reductions will include blemish removal, background (i.e., line_9: dark+scattered light) subtraction, flat fielding, wavelength registration, line_10: and conversion to flux units. The latest available HST/FOS calibration line_11: datasets will be used. Special care will be taken to determine and remove line_12: the dark background signal from the FOS observations. The following data line_13: analysis projects will be carried out: (i) Obtain calibrated spectra in flux line_14: vs wavelength for Triton between 1800 and 3278 A; (ii) Survey the Triton line_15: spectra for evidence of CO, NO, and OH in Triton's atmosphere; (iii) Measure line_16: the equivalent widths of detected absorptions in order to establish detected line_17: columns or column upper limits, and compare these to the results of the line_18: P3803 Pluto program. If S/N is available, we will measure the FWHM and line_19: general contours of detected bands. If the data are good enough, we may be line_20: able to derive constraints on the rotational temperature of the CO bands line_21: from laboratory data on their temperature-dependent rotational distribution line_22: (Gero, et al. 1937). (iv) Interpret the derived CO, NO, and OH upper limits line_23: to better understand Triton's atmospheric O-budget (and its cosmogonical ! question: 7 section: 2 line_1: implications), its atmospheric chemistry and thermal structure, its surface line_2: volatile transport rates, and its surface ice radiation processing line_3: (Thompson, et al. 1987; Johnson 1989). (v) Compare the 2500-3278 A albedo line_4: data to the three other rotational epochs previously obtained by IUE and the line_5: single rotational epoch obtained by HST in Cycle 1. (Note: To minimize line_6: observational complexity, we have not specified a preferred rotational epoch line_7: for Cycle 3; the present UV rotational phase coverage is so sparse that it line_8: virtually guarantees we will see new ``terrain''). For the data shortward of line_9: 2500 A, we will be making the first exploration of the surface reflectance. line_10: Our goals will be to determine (i) wavelength-dependent albedo; (ii) the line_11: albedo slope; and (iii) to search for subtle absorption features or edges line_12: diagnostic of Triton's surface constituents (e.g., Lebofsky and Fegley 1976; line_13: Nash and Fanale 1977; Wagner, et al. 1987). line_15: We expect two or three refereed papers to result from these analyses. ! question: 8 section: 1 line_1: Our proposal team has experience with HST (Trafton and Stern), IUE line_2: (Stern, Trafton, Gladstone, and Buratti), Voyager (Buratti and Lunine), and line_3: groundbased spectroscopy of Triton and Pluto (Trafton and Stern). S.A. Stern line_4: initiated and led the IUE studies of Triton, Pluto, and the Uranian line_5: satellites Oberon and Titania (the latter just this year). He has modelled line_6: volatile transport on both Pluto and Triton, and has conducted studies of line_7: planetary and cometary spectra. B.J. Buratti is an expert in the line_8: interpretation of groundbased and UV albedo spectra to understand planetary line_9: surface compositions and physical properties. G.R. Gladstone specializes in line_10: planetary auroral physics and atmospheric photochemistry. J.I. Lunine is a line_11: well-known expert in planetary volatiles, cosmochemistry, and the line_12: interpretation of atmospheric data sets. L.M. Trafton is an accomplished line_13: expert in planetary atmospheres, with particular experience in volatile line_14: transport and atmospheric spectroscopy in the outer solar system. He is an line_15: HST GTO and GO PI with approved spectroscopic programs on Jupiter, Io, and line_16: Pluto. A postdoc, Chan Na, will be involved in the reduction and analysis of line_17: the data. Na received his PhD from the University of Colorado under line_18: L.W. Esposito, and then joined Southwest Research Institute in August 1992. line_19: His dissertation involved the study of sulfur dioxide, sulfur monoxide, and line_20: other UV absorbers in Venus's atmosphere using UV spectra obtained by IUE, line_21: sounding rockets, and Pioneer Venus. He is presently working with PI Stern line_22: on a variety of IUE programs. ! question: 9 section: 1 line_1: P4024 High Resolution UV Spectroscopy of Triton (Stern, Trafton, Gladstone; line_2: P2560 UV Rotational Light Curves of Pluto, and Charon's UV Spectrum line_3: (Trafton, Stern); line_4: P4005 Observations of Jovian Aurora in Support of Ulysses line_5: (Stern, Trafton, Gladstone); line_6: P3803 CO Abundance and FUV Survey (Trafton, Stern); line_7: P1202 Lyman alpha H2 Survey (Trafton); line_8: P1203 Jovian Auroral Lyman alpha Profiles (Trafton); line_9: P1204 Io Proton Aurora (Trafton); line_10: P1205 SO2 on Io (Trafton); line_11: P2569 Integrated Dynamical and Spectroscopic Observations of line_12: Jupiter & Saturn (Trafton). line_15: Related HST Programs: This program is related to the 2500-3200 A Triton FOS line_16: work performed in Cycle 1 program P4024 (Stern, PI); it is broadly related line_17: to the Cycle 2 program P3803 (Trafton, PI), which will study Pluto in the line_18: deep UV. ! question: 9 section: 2 line_1: To date, none of our Pluto programs have been carried out. line_2: However, the Triton Cycle 1 (P4024) program was completed in May 1992. This line_3: single FOS spectrum of Triton is now being analyzed (Stern, et al. 1992; in line_4: preparation). This spectrum was made at a different orbital longitude (and line_5: therefore rotational epoch) than the IUE data, and has been compared to the line_6: reduced IUE spectra. It (i) confirms that Triton's UV lightcurve amplitude line_7: is higher than in any of the Voyager color filters, and (ii) shows that line_8: Triton's UV color slope varies with rotational aspect. line_9: In other programs: Images and spectra of Jupiter's aurora were line_10: taken in conjunction with the flyby of the Ulysses spacecraft (P4005, Stern; line_11: P4001, Trafton); Io's SO2 bands near 2100A were measured under P1205 line_12: (Trafton); and coordinated spectra and images of Jupiter were obtained for line_13: dynamical studies under P1260 (Trafton). The latter revealed a surprising line_14: distribution for Jupiter's aerosol haze. All of these results were presented line_15: in preliminary form at the HST workshop in Sardinia. ! question: 9 section: 3 line_1: First HST Spectroscopy of Triton: Additional Clues to UV Lightcurve line_2: Behavior. S.A. Stern, L.M. Trafton, and E.S. Barker. In preparation for line_3: Icarus, 1992. line_5: Early Results from HST Planetary Observations, L.M. Trafton. Invited paper line_6: presented to HST Workshop in Sardinia, Italy, June 29 -July 7, 1992. line_8: First results from the GHRS: Resolved velocity and density structure in the line_9: beta Pictoris circumstellar gas, A. Boggess, F.C. Bruhweiler, C.A. Grady, line_10: D.C. Ebbets, Y. Kondo, L.M. Trafton, J.C. Brandt, and S.R. Heap, ApJ. Lett., line_11: 376, 1991. ! question: 10 section: 1 line_1: line_2: Southwest Research Institute will support this project by providing line_3: workstation facilities for the PI and postdoc Na, as well as visiting CoIs. line_4: The CoI's already have workstations. The University of Arizona will line_5: contribute 0.5wm supplemental salary support for Co-I Lunine through his line_6: faculty appointment. SwRI is forgoing overhead on the salaries of postdoc Na line_7: and funded CoI Trafton. ! !end of general form text general_form_address: lname: STERN fname: S. mi: A. category: PI inst: SOUTHWEST RESEARCH INSTITUTE addr_2: SPACE SCIENCE DEPARTMENT addr_3: 6220 CULEBRA ROAD city: SAN ANTONIO state: TX zip: 78238 country: USA phone: 210-522-5127 telex: 244-846-SOUTHWESTUR ! ! end of general_form_address records ! No fixed target records found solar_system_targets: targnum: 1 name_1: TRITON descr_1: SATELLITE TRITON lev1_1: STD = NEPTUNE, ACQ = 0.1 lev2_1: STD = TRITON wind_1: WND1 = 12-MAR-93 TO 12-NOV-93, wind_2: SEP OF TRITON NEPTUNE FROM EARTH GT 11" wind_3: WITHIN WND1 comment_1: ACQUIRE TRITON VIA BINARY SEARCH. fluxnum_1: 1 fluxval_1: V = 13.7 +/- 0.2 fluxnum_2: 2 fluxval_2: TYPE = G2V fluxnum_3: 3 fluxval_3: F-CONT(2700) = 1.5 +/- 0.3 E-15 fluxnum_4: 4 fluxval_4: F-CONT(2000) = 1.7 +/- 0.5 E-16 ! targnum: 2 name_1: NEPTUNE descr_1: PLANET NEPTUNE lev1_1: STD = NEPTUNE, ACQ = 0.1 wind_1: WND1 = 12-MAR-93 TO 12-NOV-93, wind_2: SEP OF TRITON NEPTUNE FROM EARTH GT 11" wind_3: WITHIN WND1 fluxnum_1: 1 fluxval_1: V = 7.9 fluxnum_2: 2 fluxval_2: TYPE = G2V fluxnum_3: 3 fluxval_3: F-CONT(2700) = 6.5 +/- 2.6 E-13 fluxnum_4: 4 fluxval_4: F-CONT(2000) = 4.5 +/- 3.5 E-14 ! ! end of solar system targets ! No generic target records found exposure_logsheet: linenum: 1.000 targname: TRITON config: FOS/BL opmode: ACQ/BINARY aperture: 4.3 sp_element: MIRROR num_exp: 1 time_per_exp: 8.5S fluxnum_1: 1 priority: 1 req_1: ONBOARD ACQ FOR 2; req_2: CYCLE 3; req_3: GROUP 1-3 NO GAP; req_4: REPEAT 1-3 EVERY 24H +/- 9H req_5: FOR 3 MORE TIMES; comment_1: ACQ STAGE I. comment_2: LOCATE TRITON IN THE APERTURE. comment_3: EXPECT 1-2 ARCSEC ACQ ERROR. comment_4: BINARY SET UP WITH TONY KEYES comment_5: IF "REPEAT" COMMAND IS TOO comment_6: DIFFICULT TO SCHEDULE, CALL ! linenum: 2.000 targname: TRITON config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G270H wavelength: 2700 num_exp: 1 time_per_exp: 27M s_to_n: 15 s_to_n_time: 30M fluxnum_1: 3 priority: 1 req_1: SEQ 1-3; req_2: CYCLE 3; comment_1: EXPOSE TRITON G270H. comment_2: THROUGH 4.3" APERTURE. comment_3: ACCUM BL ASSUMES GIM 4M DEFAULT. ! linenum: 3.000 targname: TRITON config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G190H wavelength: 1650-2311 num_exp: 1 time_per_exp: 68M s_to_n: 6 s_to_n_time: 30M fluxnum_1: 4 priority: 1 req_1: CYCLE 3; comment_1: EXPOSE TRITON WITH G190H. comment_2: IN 4.3" APERTURE. comment_3: ACCUM BL ASSUMES GIM 4M DEFAULT. ! ! end of exposure logsheet ! No scan data records found