11540( 9) - 14-Sep-2010 13:46:47 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11540 Version: 9 Check-in Time: 14-Sep-2010 13:46:47 STScI Edit Number: 6 Title COS-GTO: Search for Hydrocarbons and Nitriles in Pluto's Atmosphere ------------------------------------------------------------------------------------ Type Cycle GTO/COS 17 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. James C. Green University of Colorado at Boulder CoI: Dr. Cynthia Froning University of Colorado at Boulder N CoI: Dr. S. Alan Stern Southwest Research Institute N CoI: Dr. John R. Spencer Southwest Research Institute Y CoI: Dr. Nathaniel J. Cunningham University of Nebraska - Lincoln N ------------------------------------------------------------------------------------ Abstract Methane is highly abundant in Pluto's atmosphere, and methane photolysis is the starting point for a series of chemical processes that should result in the production of hydrocarbons and nitriles. Photochemical modeling of Pluto's atmosphere has suggested that detectable abundances of various hydrocarbons and nitriles should occur on Pluto. However, past analysis of 40 orbits of archival HST/FOS data in the mid-UV has only produced upper limits on abundances of C4H2, C6H2, HC3N, and C4N2. We will use COS to obtain spectra from 2060-2460A, including absorption bands of the hydrocarbon diacetylene (C4H2) and the nitrile cyanoacetylene (HC3N). Previously-measured 2-sigma upper limits for these compounds are somewhat below the values computed in the poorly-constrained models; the measurement uncertainties themselves are of the same order as the modeled values. By reducing the uncertainties by a factor of a few to several, we aim to detect the presence of these compounds, or to provide more restrictive abundance limits. These measurements will provide valuable new data on the nature and chemistry of the Plutonian atmosphere. ------------------------------------------------------------------------------------ Observations Description ------------------------ COS NUV spectra of Pluto from 2060 to 2460A using G230L at 3360A central wavelength, for a total of 5 orbits. Only one grating position (central wavelength) is required to cover the specified wavelength band. Observations will be divided into two visits: 2 orbits at one central meridional longitude, and 3 orbits at another; in this way, the spectra can be coadded for the greatest signal-to-noise, and compared to look for longitude-specific differences in absorption spectrum. The chosen longitudes (90 and 270 degrees) correspond to greatest angular separation of Charon from Pluto, reaching 0.85"; the position angle (CCW from north) of Charon from Pluto is about 153 and 333 degrees for these cases. ORIENT is specified in order to minimize spectral confusion, by aligning Charon in the cross-dispersion direction. Real Time Justification ----------------------- 11540( 9) - 14-Sep-2010 13:46:47 - [ 2] Calibration Justification ------------------------- Additional Comments ------------------- ORIENT calculation: U3 axis is at 135 degrees from COS +Y (spatial) direction, and at 135+180 = 315 degrees from -Y With Pluto viewed at CML = 90, Charon is near position angle 153 degrees; Pluto-Charon vector can extend along either +Y or -Y. So we have ORIENT near 135+153 = 288 degrees or near 315 + 153 = 468 ==> 108 degrees. With Pluto viewed at CML = 270, Charon is near position angle 333 degrees (180 degrees from above). Same calculation as above -- 135 + 333 ==> 108 degrees orient, 315 + 333 ==> 288 degrees. We've specified the desired CML +/- 15 degrees, which provides ~12 hr obs windows; ORIENT window of +/- 5 degrees keeps 4+ months available. ------------------------------------------------------------------------------------ 11540( 9) - 14-Sep-2010 13:46:47 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: PLUTO-90LONG ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET PLANET PLUTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=PLUTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS CML OF PLUTO FROM EARTH BETWEEN 80 100 ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 14.0 +/- 0.5 about 1 magnitude dimmer in mid-UV relative to visible, F(2400)=1E-16 based on albedo measurements -- 0.2 - 0.25 in mid UV, instead of 0.5 - 0.66 in visible Ephemeris Center: EARTH (used mV = 15 solar-type spectrum for ETC) Specified window -- CML of 90+/-10 degrees -- puts Charon near largest separation from Pluto, and at position angle near 150 degrees. ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 TARGET NAME: PLUTO-270LONG ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET PLANET PLUTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=PLUTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS CML OF PLUTO FROM EARTH BETWEEN 260 280 ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 14.0 +/- 0.5 Specified window -- CML of 270+/-10 degrees -- puts F(2400)=1E-16 Charon near largest separation from Pluto, and at position angle near 330 degrees. Ephemeris Center: EARTH ------------------------------------------------------------------------------------------------------------------------------------ 11540( 9) - 14-Sep-2010 13:46:47 - [ 4] Visit: 01 Visit Requirements: ORIENT 105D TO 110 D; BETWEEN 30-AUG-2010:00:00:00 AND 30-SEP-2010:23:59:59 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PLUTO-90LON COS/NUV ACQ/SEA PSA MIRRORA SCAN-SIZE=2 1 25 S GS ACQ SCENARIO BASE1B3 G RCH ------------------------------------------------------------------------------------------------------------------------------------ 2 PLUTO-90LON COS/NUV ACQ/IMA PSA MIRRORA 1 25 S G GE Comments: COS ETC: COS75940 for estimation of acquisition time. Assumed solar-type Kurucz spectrum with effective m_V=15.0, normal airglow. ------------------------------------------------------------------------------------------------------------------------------------ 3 PLUTO-90LON COS/NUV TIME-TA PSA G230L 3360 BUFFER-TIME=1970, FP-POS=2 1 1970 S G G Comments: ETC: COS75942 gives buffer-time of 2/3 * 10327s ------------------------------------------------------------------------------------------------------------------------------------ 4 PLUTO-90LON COS/NUV TIME-TA PSA G230L 3360 BUFFER-TIME=2971, FP-POS=3 1 2971 S G G ------------------------------------------------------------------------------------------------------------------------------------ 5 PLUTO-90LON COS/NUV TIME-TA PSA G230L 3360 BUFFER-TIME=2971, FP-POS=4 1 2971 S G G ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ PLUTO-90LONG 1 COS/NUV ACQ/SEA PSA MIRRORA none none none none 1 N/A RCH PLUTO-90LONG 2 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE PLUTO-90LONG 3 COS/NUV TIME-TA PSA G230L 3360 none none none none 1 N/A G PLUTO-90LONG 4 COS/NUV TIME-TA PSA G230L 3360 none none none none 2 N/A G PLUTO-90LONG 5 COS/NUV TIME-TA PSA G230L 3360 none none none none 3 N/A G 11540( 9) - 14-Sep-2010 13:46:47 - [ 5] Visit: 02 Visit Requirements: ORIENT 280D TO 290 D; ORIENT 100D TO 110 D; BETWEEN 01-SEP-2010:00:00:00 AND 30-SEP-2010:23:59:59 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PLUTO-270LO COS/NUV ACQ/SEA PSA MIRRORA SCAN-SIZE=2 1 25 S GS ACQ SCENARIO BASE1B3 NG RCH ------------------------------------------------------------------------------------------------------------------------------------ 2 PLUTO-270LO COS/NUV ACQ/IMA PSA MIRRORA 1 25 S NG GE ------------------------------------------------------------------------------------------------------------------------------------ 3 PLUTO-270LO COS/NUV TIME-TA PSA G230L 3360 BUFFER-TIME=1970, FP-POS=2 1 1970 S NG G ------------------------------------------------------------------------------------------------------------------------------------ 4 PLUTO-270LO COS/NUV TIME-TA PSA G230L 3360 BUFFER-TIME=1335, FP-POS=3 1 1445 S NG G ------------------------------------------------------------------------------------------------------------------------------------ 5 PLUTO-270LO COS/NUV TIME-TA PSA G230L 3360 BUFFER-TIME=1445, FP-POS=4 1 1445 S NG G ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ PLUTO-270LONG 1 COS/NUV ACQ/SEA PSA MIRRORA none none none none 1 N/A RCH PLUTO-270LONG 2 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE PLUTO-270LONG 3 COS/NUV TIME-TA PSA G230L 3360 none none none none 1 N/A G PLUTO-270LONG 4 COS/NUV TIME-TA PSA G230L 3360 none none none none 2 N/A G PLUTO-270LONG 5 COS/NUV TIME-TA PSA G230L 3360 none none none none 2 N/A G 11540( 9) - 14-Sep-2010 13:46:47 - [ 6] Visit: 03 Visit Requirements: ORIENT 280D TO 290 D; ORIENT 75D TO 135 D; BETWEEN 01-SEP-2010:00:00:00 AND 31-OCT-2010:23:59:59 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PLUTO-270LO COS/NUV ACQ/SEA PSA MIRRORA SCAN-SIZE=2 1 25 S GS ACQ SCENARIO BASE1B3 NG RCH ------------------------------------------------------------------------------------------------------------------------------------ 2 PLUTO-270LO COS/NUV ACQ/IMA PSA MIRRORA 1 25 S NG GE ------------------------------------------------------------------------------------------------------------------------------------ 3 PLUTO-270LO COS/NUV TIME-TA PSA G230L 3360 BUFFER-TIME=1970, FP-POS=2 1 1970 S NG G ------------------------------------------------------------------------------------------------------------------------------------ 4 PLUTO-270LO COS/NUV TIME-TA PSA G230L 3360 BUFFER-TIME=1335, FP-POS=3 1 1445 S NG G ------------------------------------------------------------------------------------------------------------------------------------ 5 PLUTO-270LO COS/NUV TIME-TA PSA G230L 3360 BUFFER-TIME=1445, FP-POS=4 1 1445 S NG G ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ PLUTO-270LONG 1 COS/NUV ACQ/SEA PSA MIRRORA none none none none 1 N/A RCH PLUTO-270LONG 2 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE PLUTO-270LONG 3 COS/NUV TIME-TA PSA G230L 3360 none none none none 1 N/A G PLUTO-270LONG 4 COS/NUV TIME-TA PSA G230L 3360 none none none none 2 N/A G PLUTO-270LONG 5 COS/NUV TIME-TA PSA G230L 3360 none none none none 2 N/A G 11540( 9) - 14-Sep-2010 13:46:47 - [ 7] Summary Form for Proposal 11540 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, ACQ/SEARCH, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1335, BUFFER-TIME=1445, BUFFER-TIME=1970, BUFFER-TIME=2971, FP-POS=2, FP-POS=3, FP-POS=4, SCAN-SIZE=2 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 01-SEP-2010:00:00:00 AND 30-SEP-2010:23:59:59, BETWEEN 01-SEP-2010:00:00:00 AND 31-OCT-2010:23:59:59, BETWEEN 30-AUG-2010:00:00:00 AND 30-SEP-2010:23:59:59, GS ACQ SCENARIO BASE1B3, ORIENT 100D TO 110 D, ORIENT 105D TO 110 D, ORIENT 280D TO 290 D, ORIENT 75D TO 135 D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G230L, MIRRORA ------------------------------------------------------------------------------------------------------------------------------------ Target Names PLUTO-270LONG, PLUTO-90LONG ------------------------------------------------------------------------------------------------------------------------------------