14106( 13) - 29-Sep-2016 13:18:56 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14106 Version: 13 Check-in Time: 29-Sep-2016 13:18:56 STScI Edit Number: 5 Title Probing Ceres' exosphere and water vapor outgassing ------------------------------------------------------------------------------------ Type Cycle GO 23 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Lorenz Roth Royal Institute of Technology Y CoI: Dr. Kurt David Retherford Southwest Research Institute N CoI: Dr. Nickolay Ivchenko Royal Institute of Technology N CoI: Dr. Paul D. Feldman The Johns Hopkins University N CoI: Dr. Joachim Saur Universitat zu Koeln N CoI: Dr. John R. Spencer Southwest Research Institute N CoI: Dr. Darrell F. Strobel The Johns Hopkins University N CoI: Dr. Nathaniel J. Cunningham Nebraska Wesleyan University N ------------------------------------------------------------------------------------ Abstract Evidence is mounting that Ceres is a geophysically active icy world. The Herschel telescope measured water vapor above two surface regions and first-view images by the Dawn spacecraft suggest active outgassing above bright, intriguing surface features. Dawn will be in orbit probing the interior and surface of Ceres at least until the end of 2015. The high sensitivity and high resolution of COS provide the unique possibility to obtain supporting FUV spectra to constrain Ceres' exosphere and outgassing. We propose 5 consecutive orbits in the COS G130M mode to measure atomic emissions from O, H and possible trace species in the exosphere. During the ~7.5-hour long visit Ceres' active regions will be targeted on the dayside. Observed diurnal variations will be used to independently differentiate between sublimation and liquid reservoir source regions and detected exospheric signals will be related to surface features characterized by Dawn. ------------------------------------------------------------------------------------ Observations Description ------------------------ We use the COS G130M mode centered at 1291 A for the two wavelength ranges of 1134 A to 1274 A (Segment A) and 1291 A 1431 A (Segment B) that include the most important oxygen lines at 1304 and observe over almost one full Ceres rotation period (7.5 hours out of 9.1 hours). We will locate Ceres with a small offset of ~0.5 arcsec in the lower part of the 2.5 arcsec pinhole in order to be able to simultaneously measure both Ceres and the sky background. ------------------------------------------------------------------------------------ 14106( 13) - 29-Sep-2016 13:18:56 - [ 2] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: CERES-ACQ ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: DWARF-PLANET DWARF-PLANET CERES ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=CERES ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 8 +/- 1.4 The diameter of Ceres is roughly 0.6 arcsec in the sky near Ceres opposition, so that it falls just in the category of extended sources for COS. The CERES-ACQ Ephemeris Center: EARTH target does not have observing window requirements, while Extended: YES the CERES target (for the science exposures) includes "CML OF CERES" requirements. ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 TARGET NAME: CERES ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: DWARF-PLANET OFFSET DWARF-PLANET CERES ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=CERES ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS NOT CML OF CERES-ACQ FROM EARTH BETWEEN 340 20 ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 8 +/- 1.4 The diameter of Ceres is roughly 0.6 arcsec in the sky near Ceres opposition, so that it falls just in the category of extended sources for COS. The CERES-ACQ Ephemeris Center: EARTH target does not have observing window requirements, while Extended: YES the CERES target (for the science exposures) includes "CML OF CERES" requirements. ------------------------------------------------------------------------------------------------------------------------------------ 14106( 13) - 29-Sep-2016 13:18:56 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 3 TARGET NAME: CERES-COPY ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: DWARF-PLANET OFFSET DWARF-PLANET CERES ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=CERES ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 8 +/- 1.4 The diameter of Ceres is roughly 0.6 arcsec in the sky near Ceres opposition, so that it falls just in the category of extended sources for COS. Ephemeris Center: EARTH Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 14106( 13) - 29-Sep-2016 13:18:56 - [ 4] Visit: 01 Visit Requirements: BETWEEN 10-JUL-2015:00:00:00 AND 30-SEP-2015:00:00:00 On Hold Comments: Additional Comments: - For acquisition, we use only ACQ/IMAGE with Mirror A assuming that the coordinates of Ceres are known with an accuracy smaller than 0.4''. The ETC yields SNR=40 in 0.0234 seconds for the normalized solar spectrum and the exposure time of 5 second should give good margin. - For the science exposures, the target has an offset of y = -0.5'' to locate Ceres in the lower half of the aperture. This way we can analyze the sky background only in the upper half of the detector. Ceres is located in the lower half, as the upper half might suffer a gain-sag from the previous lifetime position on the COS detector. The gain-sag might affect the sky background, but the primarily targeted OI lines fall on segment A, which is less strongly affected. - We take 2 science exposures per orbit cycling consecutively through the FP-POS positions. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CERES COS/NUV ACQ/IMA PSA MIRRORA 1 10 S (10 GS ACQ SCENARIO BASE1B3 GE S) Comments: For the ETC, a SED of Ceres' surface brightness between 1200 and 4200 A was generated with a solar spectrum for average solar wind acitivity from UARS. The spectrum was scaled to Ceres' distance to the sun of ~2.9 AU during the observation and with an interpolated geometric albedo based on the albedo values from Li et al., 2006, Icarus. The ETC run for extended source yield a SNR of 40 after 1.1 seconds, so we choose 10 seconds for a sufficient margin. A imaging ETC run (not TA) was also performed: COS.ta.727578 ------------------------------------------------------------------------------------------------------------------------------------ 2 CERES COS/FUV TIME-TA PSA G130M 1291 FP-POS=1, BUFFER-TIME=3000 1 2000 S POS TARG null, -0.5; GS G see below ACQ SCENARIO BASE1B3 (2361 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 CERES COS/FUV TIME-TA PSA G130M 1291 FP-POS=2, BUFFER-TIME=3000 1 2700 S POS TARG 0, 0.5 G see below (2912 S) Comments: ETC buffer time calculations yields times larger than exposure time of ~1200 sec, so buffer time is set to exposure time ------------------------------------------------------------------------------------------------------------------------------------ 14106( 13) - 29-Sep-2016 13:18:56 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 4 CERES COS/FUV TIME-TA PSA G130M 1291 FP-POS=3, BUFFER-TIME=3000 1 2700 S SAME POS AS 2 G see below (2912 S) Comments: ETC buffer time calculations yields times larger than exposure time of ~1200 sec, so buffer time is set to exposure time ------------------------------------------------------------------------------------------------------------------------------------ 5 CERES COS/FUV TIME-TA PSA G130M 1291 FP-POS=3, BUFFER-TIME=3000 1 2700 S SAME POS AS 3 G see below (2915 S) Comments: ETC buffer time calculations yields times larger than exposure time of ~1200 sec, so buffer time is set to exposure time ------------------------------------------------------------------------------------------------------------------------------------ 6 CERES COS/FUV TIME-TA PSA G130M 1291 FP-POS=4, BUFFER-TIME=3000 1 2700 S SAME POS AS 2 G see below (2912 S) Comments: ETC buffer time calculations yields times larger than exposure time of ~1200 sec, so buffer time is set to exposure time ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ CERES 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE CERES 2 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 2361.0 S G CERES 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 2912.0 S G CERES 4 COS/FUV TIME-TA PSA G130M 1291 none none none none 3 2912.0 S G CERES 5 COS/FUV TIME-TA PSA G130M 1291 none none none none 4 2915.0 S G CERES 6 COS/FUV TIME-TA PSA G130M 1291 none none none none 5 2912.0 S G 14106( 13) - 29-Sep-2016 13:18:56 - [ 6] Visit: 02 Visit Requirements: SCHED 80%; BETWEEN 17-OCT-2016:00:00:00 AND 08-NOV-2016:00:00:00 On Hold Comments: Additional Comments: - For the science exposures, the target has an offset of y = -1.85'' to locate Ceres just outside the aperture allowing an location error of 0.3". This way we get only the signal from the exosphere without contributions from bright surface reflected light. - The last science exposure target 20" away from Ceres to get a comparable sky background (minimal exosphere contributions) - We cycle consecutively through the FP-POS positions, repeating POS=4 in the fifth exposure. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CERES-COPY COS/NUV ACQ/SEA PSA G230L 3000 SCAN-SIZE=3, 1 2 S (2 S) GS ACQ SCENARIO BASE1B3 RCH CENTER=FLUX-WT-FLR Comments: For the ETC, a SED of Ceres' surface brightness between 1200 and 4200 A was generated with a solar spectrum for average solar wind acitivity from UARS. The spectrum was scaled to Ceres' distance to the sun of ~2.9 AU during the observation and with an interpolated geometric albedo based on the albedo values from Li et al., 2006, Icarus. The ETC run for extended source yield a SNR of 40 after 1.1 seconds, so we choose 10 seconds for a sufficient margin. A imaging ETC run (not TA) was also performed: COS.ta.727578 ------------------------------------------------------------------------------------------------------------------------------------ 2 CERES-COPY COS/FUV TIME-TA PSA G130M 1327 FP-POS=1, BUFFER-TIME=3000 1 1800 S POS TARG null, -1.95 G see below (1904 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 CERES-COPY COS/FUV TIME-TA PSA G130M 1327 FP-POS=2, BUFFER-TIME=3000 1 2700 S SAME POS AS 2 G see below (2737 S) Comments: ETC buffer time calculations yields times larger than exposure time of ~1200 sec, so buffer time is set to exposure time ------------------------------------------------------------------------------------------------------------------------------------ 14106( 13) - 29-Sep-2016 13:18:56 - [ 7] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 4 CERES-COPY COS/FUV TIME-TA PSA G130M 1327 FP-POS=3, BUFFER-TIME=3000 1 2700 S SAME POS AS 2 G see below (2737 S) Comments: ETC buffer time calculations yields times larger than exposure time of ~1200 sec, so buffer time is set to exposure time ------------------------------------------------------------------------------------------------------------------------------------ 5 CERES-COPY COS/FUV TIME-TA PSA G130M 1327 FP-POS=4, BUFFER-TIME=3000 1 2700 S SAME POS AS 2 G see below (2737 S) Comments: ETC buffer time calculations yields times larger than exposure time of ~1200 sec, so buffer time is set to exposure time ------------------------------------------------------------------------------------------------------------------------------------ 6 CERES-COPY COS/FUV TIME-TA PSA G130M 1327 FP-POS=4, BUFFER-TIME=3000 1 2700 S POS TARG null, -20; NEW G see below OBSET FULL ACQ; GS ACQ (2550 S) SCENARIO BASE1B3 Comments: ETC buffer time calculations yields times larger than exposure time of ~1200 sec, so buffer time is set to exposure time ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ CERES-COPY 1 COS/NUV ACQ/SEA PSA G230L 3000 none none none none 1 N/A RCH CERES-COPY 2 COS/FUV TIME-TA PSA G130M 1327 none none none none 1 1904.0 S G CERES-COPY 3 COS/FUV TIME-TA PSA G130M 1327 none none none none 2 2737.0 S G CERES-COPY 4 COS/FUV TIME-TA PSA G130M 1327 none none none none 3 2737.0 S G CERES-COPY 5 COS/FUV TIME-TA PSA G130M 1327 none none none none 4 2737.0 S G CERES-COPY 6 COS/FUV TIME-TA PSA G130M 1327 none none none none 5 2550.0 S G 14106( 13) - 29-Sep-2016 13:18:56 - [ 8] Summary Form for Proposal 14106 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, ACQ/SEARCH, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=3000, CENTER=FLUX-WT-FLR, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4, SCAN-SIZE=3 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 10-JUL-2015:00:00:00 AND 30-SEP-2015:00:00:00, BETWEEN 17-OCT-2016:00:00:00 AND 08-NOV-2016:00:00:00, GS ACQ SCENARIO BASE1B3, NEW OBSET FULL ACQ, POS TARG 0, 0.5, POS TARG null, -0.5, POS TARG null, -1.95, POS TARG null, -20, SAME POS AS 2, SAME POS AS 3, SCHED 80% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, G230L, MIRRORA ------------------------------------------------------------------------------------------------------------------------------------ Target Names CERES, CERES-COPY ------------------------------------------------------------------------------------------------------------------------------------