14755( 2) - 21-Jul-2016 14:40:53 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14755 Version: 2 Check-in Time: 21-Jul-2016 14:40:53 STScI Edit Number: 1 Title Understanding Callisto's Atmosphere ------------------------------------------------------------------------------------ Type Cycle GO 24 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. John R. Spencer Southwest Research Institute Y CoI: Dr. Nathaniel J. Cunningham Nebraska Wesleyan University N CoI: Dr. Darrell F. Strobel The Johns Hopkins University N CoI: Dr. Paul D. Feldman The Johns Hopkins University N CoI: Dr. Lorenz Roth Royal Institute of Technology N CoI: Dr. Joachim Saur Universitat zu Koeln N CoI: Mr. Oliver Hartkorn Universitat zu Koeln N ------------------------------------------------------------------------------------ Abstract We plan to address first-order questions about the nature and origin of the mysterious atmosphere of Callisto, including its composition, longitudinal distribution, formation, and support mechanisms. This investigation is made possible by the remarkable sensitivity of the COS instrument, which has recently detected faint 1304 A and 1356 A O I emission from Callisto's leading / Jupiter-facing quadrant. The emission is probably due to dissociation of O2 molecules in Callisto's atmosphere by photo-electrons, and resonant scattering from an extended atomic O corona. We suspect, from Galileo ionospheric data, that the atmosphere may be much denser, and brighter in emission, on the trailing hemisphere, as expected for a sputter-generated atmosphere, and propose to test the sputter generation hypothesis with 4-orbit COS integrations on the leading and trailing hemispheres. If the trailing side emissions are indeed brighter, the improved SNR there will also allow much improved determination of atmospheric and coronal composition and optical depth. The observations will set the stage for, and aid in planning of, the extensive observations of Callisto's environment planned for the JUICE mission. Because Callisto's atmospheric oxygen emissions are indirectly illuminated by sunlight, which is uniform and quantifiable, it is much easier to understand atmospheric spatial distribution, and thus origin, than on Europa and Ganymede were emissions depend on magnetospheric excitation which is spatially variable and poorly understood. Callisto's atmosphere thus provides a unique chance to better understand the oxygen atmospheres of all the icy Galilean moons. ------------------------------------------------------------------------------------ Observations Description ------------------------ Four orbits with the G130M grating at 1300?, to achieve >= 8000s. ------------------------------------------------------------------------------------ 14755( 2) - 21-Jul-2016 14:40:53 - [ 2] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: CALLISTO-LEADING ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE CALLISTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=JUPITER STD=CALLISTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS SEP OF CALLISTO-LEADING JUPITER FROM EARTH GT 30", SEP OF CALLISTO-LEADING IO FROM EARTH GT 10", SEP OF CALLISTO-LEADING EUROPA FROM EARTH GT 10", SEP OF CALLISTO-LEADING GANYMEDE FROM EARTH GT 10", OLG OF CALLISTO-LEADING FROM EARTH BETWEEN 60 120, SEP OF CALLISTO-LEADING SUN FROM EARTH GT 160D ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 6.1 +/- 1 As the oxygen lines to be observed are also present in F(1356 A) = 3 Rayleigh terrestrial airglow, we choose to observe near opposition to maximize time in Earth's shadow. We specify this by Ephemeris Center: EARTH requiring that the solar elongation of Callisto be Extended: YES greater than 160 degrees ------------------------------------------------------------------------------------------------------------------------------------ 14755( 2) - 21-Jul-2016 14:40:53 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 TARGET NAME: CALLISTO-TRAILING ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE CALLISTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=JUPITER STD=CALLISTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS SEP OF CALLISTO-TRAILING JUPITER FROM EARTH GT 30", SEP OF CALLISTO-TRAILING IO FROM EARTH GT 10", SEP OF CALLISTO-TRAILING EUROPA FROM EARTH GT 10", SEP OF CALLISTO-TRAILING GANYMEDE FROM EARTH GT 10", OLG OF CALLISTO-TRAILING FROM EARTH BETWEEN 240 300, SEP OF CALLISTO-TRAILING SUN FROM EARTH GT 160D ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 6.1 +/- 1 As the oxygen lines to be observed are also present in F(1356 A) = 3 Rayleigh terrestrial airglow, we choose to observe near opposition to maximize time in Earth's shadow. We specify this by Ephemeris Center: EARTH requiring that the solar elongation of Callisto be Extended: YES greater than 160 degrees ------------------------------------------------------------------------------------------------------------------------------------ 14755( 2) - 21-Jul-2016 14:40:53 - [ 4] Visit: 01 (Trailing Hemisphere) Visit Requirements: SCHED 80% On Hold Comments: Additional Comments: * We use four consecutive orbits to minimize exposure time loss due to acquisition * For the first two orbits, after acquisition, Callisto is offset 0.9" in the aperture- an identical strategy to visit 4 of our previous program 11535 * For the second two orbits, we use the second half of orbit 3 and the first half of orbit 4 to characterize the background 5" away from Callisto, at the same HST orbital position as integrations centered on Callisto in the first half of orbit 3 and the second half of orbit 4. For each of these integrations we use just 2 FP-POS positions to minimize overhead 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 CALLISTO-TR COS/NUV ACQ/SEA PSA G285M 2709 SCAN-SIZE=3 1 5 S (5 S) GS ACQ SCENARIO BASE1B3 AILING RCH Comments: Callisto is 6.2 +/- 0.5 mags over 2009 (based on JPL ephem generator), and is effectively 1.1 mag dimmer in this grating bandpass than in the visible (based on albedo = 0.06 here vs. 0.17 in visible). So I use mV_effective = 7.3 and get 0.44/0.96 seconds for ACQ-Search/ACQ-PeakXD modes to reach S/N = 40 (ETC IDs COS78131 / COS78132). 5 seconds gives plenty of margin ------------------------------------------------------------------------------------------------------------------------------------ 2 CALLISTO-TR COS/NUV ACQ/PEA PSA G285M 2709 1 5 S (5 S) AILING KXD Comments: Callisto is 6.2 +/- 0.5 mags over 2009 (based on JPL ephem generator), and is effectively 1.1 mag dimmer in this grating bandpass than in the visible (based on albedo = 0.06 here vs. 0.17 in visible). So I use mV_effective = 7.3 and get 0.44/0.96 seconds for ACQ-Search/ACQ-PeakXD modes to reach S/N = 40 (ETC IDs COS78131 / COS78132) ------------------------------------------------------------------------------------------------------------------------------------ 3 CALLISTO-TR COS/NUV ACQ/PEA PSA G285M 2709 NUM-POS=7, STEP-SIZE=1.2 1 5 S (5 S) AILING KD Comments: estimates are same as for exposure 1, ACQ/SEARCH ------------------------------------------------------------------------------------------------------------------------------------ 14755( 2) - 21-Jul-2016 14:40:53 - [ 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 CALLISTO-TR COS/FUV TIME-TA PSA G130M 1291 FP-POS=1, BUFFER-TIME=1712 1 1450 S POS TARG 0, -0.9 AILING G (1450 S) Comments: COS76584 for calculation of buffer time. Assumes effective mV = 6.8 and 15 Rayleigh (8.2e-16 ergs/cm^2/s) 1356? line. Gives buffer time = 2/3 * 5939s. POS TARG is designed to place Callisto 0.9" in the cross-dispersion (+Y) direction. This is intended to allow a portion of the the aperture, and therefore a portion of the spectrum, to contain purely airglow, while the upper part of the aperture contains Callisto's spectrum in addition to oxygen airglow. The cross-dispersion variation in oxygen emission line intensity will help indicate whether Callisto has a significant additional oxygen signal. ------------------------------------------------------------------------------------------------------------------------------------ 5 CALLISTO-TR COS/FUV TIME-TA PSA G130M 1291 FP-POS=2, BUFFER-TIME=1298 1 1250 S SAME POS AS 4 AILING G (1250 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 CALLISTO-TR COS/FUV TIME-TA PSA G130M 1291 FP-POS=4, BUFFER-TIME=1408 1 1250 S SAME POS AS 4 AILING G (1250 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 CALLISTO-TR COS/FUV TIME-TA PSA G130M 1291 FP-POS=1, BUFFER-TIME=1408 1 540 S (540 AILING G S) ------------------------------------------------------------------------------------------------------------------------------------ 8 CALLISTO-TR COS/FUV TIME-TA PSA G130M 1291 FP-POS=3, BUFFER-TIME=1408 1 540 S (540 AILING G S) ------------------------------------------------------------------------------------------------------------------------------------ 9 CALLISTO-TR COS/FUV TIME-TA PSA G130M 1291 FP-POS=1, BUFFER-TIME=1408 1 540 S (540 POS TARG null, 5 AILING G S) ------------------------------------------------------------------------------------------------------------------------------------ 10 CALLISTO-TR COS/FUV TIME-TA PSA G130M 1291 FP-POS=3, BUFFER-TIME=1408 1 540 S (540 SAME POS AS 9 AILING G S) ------------------------------------------------------------------------------------------------------------------------------------ 11 CALLISTO-TR COS/FUV TIME-TA PSA G130M 1291 FP-POS=1, BUFFER-TIME=1408 1 540 S (540 SAME POS AS 9 AILING G S) ------------------------------------------------------------------------------------------------------------------------------------ 12 CALLISTO-TR COS/FUV TIME-TA PSA G130M 1291 FP-POS=3, BUFFER-TIME=1408 1 540 S (540 SAME POS AS 9 AILING G S) ------------------------------------------------------------------------------------------------------------------------------------ 13 CALLISTO-TR COS/FUV TIME-TA PSA G130M 1291 FP-POS=1, BUFFER-TIME=1408 1 540 S (540 AILING G S) ------------------------------------------------------------------------------------------------------------------------------------ 14755( 2) - 21-Jul-2016 14:40:53 - [ 6] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 14 CALLISTO-TR COS/FUV TIME-TA PSA G130M 1291 FP-POS=3, BUFFER-TIME=1408 1 540 S (540 AILING G S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ CALLISTO-TRAILING 1 COS/NUV ACQ/SEA PSA G285M 2709 none none none none 1 N/A RCH CALLISTO-TRAILING 2 COS/NUV ACQ/PEA PSA G285M 2709 none none none none 1 N/A KXD CALLISTO-TRAILING 3 COS/NUV ACQ/PEA PSA G285M 2709 none none none none 1 N/A KD CALLISTO-TRAILING 4 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G CALLISTO-TRAILING 5 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G CALLISTO-TRAILING 6 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G CALLISTO-TRAILING 7 COS/FUV TIME-TA PSA G130M 1291 none none none none 3 N/A G CALLISTO-TRAILING 8 COS/FUV TIME-TA PSA G130M 1291 none none none none 3 N/A G CALLISTO-TRAILING 9 COS/FUV TIME-TA PSA G130M 1291 none none none none 3 N/A G CALLISTO-TRAILING 10 COS/FUV TIME-TA PSA G130M 1291 none none none none 3 N/A G CALLISTO-TRAILING 11 COS/FUV TIME-TA PSA G130M 1291 none none none none 4 N/A G CALLISTO-TRAILING 12 COS/FUV TIME-TA PSA G130M 1291 none none none none 4 N/A G CALLISTO-TRAILING 13 COS/FUV TIME-TA PSA G130M 1291 none none none none 4 N/A G CALLISTO-TRAILING 14 COS/FUV TIME-TA PSA G130M 1291 none none none none 4 N/A G 14755( 2) - 21-Jul-2016 14:40:53 - [ 7] Visit: 02 (Leading Hemisphere) Visit Requirements: SCHED 80% On Hold Comments: Additional Comments: * We use four consecutive orbits to minimize exposure time loss due to acquisition * For the first two orbits, after acquisition, Callisto is offset 0.9" in the aperture- an identical strategy to visit 4 of our previous program 11535 * For the second two orbits, we use the second half of orbit 3 and the first half of orbit 4 to characterize the background 5" away from Callisto, at the same HST orbital position as integrations centered on Callisto in the first half of orbit 3 and the second half of orbit 4. For each of these integrations we use just 2 FP-POS positions to minimize overhead 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 CALLISTO-LE COS/NUV ACQ/SEA PSA G285M 2709 SCAN-SIZE=3 1 5 S (5 S) GS ACQ SCENARIO BASE1B3 ADING RCH Comments: Callisto is 6.2 +/- 0.5 mags over 2009 (based on JPL ephem generator), and is effectively 1.1 mag dimmer in this grating bandpass than in the visible (based on albedo = 0.06 here vs. 0.17 in visible). So I use mV_effective = 7.3 and get 0.44/0.96 seconds for ACQ-Search/ACQ-PeakXD modes to reach S/N = 40 (ETC IDs COS78131 / COS78132). 5 seconds gives plenty of margin ------------------------------------------------------------------------------------------------------------------------------------ 2 CALLISTO-LE COS/NUV ACQ/PEA PSA G285M 2709 1 5 S (5 S) ADING KXD Comments: Callisto is 6.2 +/- 0.5 mags over 2009 (based on JPL ephem generator), and is effectively 1.1 mag dimmer in this grating bandpass than in the visible (based on albedo = 0.06 here vs. 0.17 in visible). So I use mV_effective = 7.3 and get 0.44/0.96 seconds for ACQ-Search/ACQ-PeakXD modes to reach S/N = 40 (ETC IDs COS78131 / COS78132) ------------------------------------------------------------------------------------------------------------------------------------ 3 CALLISTO-LE COS/NUV ACQ/PEA PSA G285M 2709 NUM-POS=7, STEP-SIZE=1.2 1 5 S (5 S) ADING KD Comments: estimates are same as for exposure 1, ACQ/SEARCH ------------------------------------------------------------------------------------------------------------------------------------ 14755( 2) - 21-Jul-2016 14:40:53 - [ 8] 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 CALLISTO-LE COS/FUV TIME-TA PSA G130M 1291 FP-POS=1, BUFFER-TIME=1712 1 1450 S POS TARG 0, -0.9 ADING G (1450 S) Comments: COS76584 for calculation of buffer time. Assumes effective mV = 6.8 and 15 Rayleigh (8.2e-16 ergs/cm^2/s) 1356? line. Gives buffer time = 2/3 * 5939s. POS TARG is designed to place Callisto 0.9" in the cross-dispersion (+Y) direction. This is intended to allow a portion of the the aperture, and therefore a portion of the spectrum, to contain purely airglow, while the upper part of the aperture contains Callisto's spectrum in addition to oxygen airglow. The cross-dispersion variation in oxygen emission line intensity will help indicate whether Callisto has a significant additional oxygen signal. ------------------------------------------------------------------------------------------------------------------------------------ 5 CALLISTO-LE COS/FUV TIME-TA PSA G130M 1291 FP-POS=2, BUFFER-TIME=1298 1 1250 S SAME POS AS 4 ADING G (1250 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 CALLISTO-LE COS/FUV TIME-TA PSA G130M 1291 FP-POS=4, BUFFER-TIME=1408 1 1250 S SAME POS AS 4 ADING G (1250 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 CALLISTO-LE COS/FUV TIME-TA PSA G130M 1291 FP-POS=2, BUFFER-TIME=1408 1 540 S (540 ADING G S) ------------------------------------------------------------------------------------------------------------------------------------ 8 CALLISTO-LE COS/FUV TIME-TA PSA G130M 1291 FP-POS=4, BUFFER-TIME=1408 1 540 S (540 ADING G S) ------------------------------------------------------------------------------------------------------------------------------------ 9 CALLISTO-LE COS/FUV TIME-TA PSA G130M 1291 FP-POS=2, BUFFER-TIME=1408 1 540 S (540 POS TARG null, 5 ADING G S) ------------------------------------------------------------------------------------------------------------------------------------ 10 CALLISTO-LE COS/FUV TIME-TA PSA G130M 1291 FP-POS=4, BUFFER-TIME=1408 1 540 S (540 SAME POS AS 9 ADING G S) ------------------------------------------------------------------------------------------------------------------------------------ 11 CALLISTO-LE COS/FUV TIME-TA PSA G130M 1291 FP-POS=2, BUFFER-TIME=1408 1 540 S (540 SAME POS AS 9 ADING G S) ------------------------------------------------------------------------------------------------------------------------------------ 12 CALLISTO-LE COS/FUV TIME-TA PSA G130M 1291 FP-POS=4, BUFFER-TIME=1408 1 540 S (540 SAME POS AS 9 ADING G S) ------------------------------------------------------------------------------------------------------------------------------------ 13 CALLISTO-LE COS/FUV TIME-TA PSA G130M 1291 FP-POS=2, BUFFER-TIME=1408 1 540 S (540 ADING G S) ------------------------------------------------------------------------------------------------------------------------------------ 14755( 2) - 21-Jul-2016 14:40:53 - [ 9] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 14 CALLISTO-LE COS/FUV TIME-TA PSA G130M 1291 FP-POS=4, BUFFER-TIME=1408 1 540 S (540 ADING G S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ CALLISTO-LEADING 1 COS/NUV ACQ/SEA PSA G285M 2709 none none none none 1 N/A RCH CALLISTO-LEADING 2 COS/NUV ACQ/PEA PSA G285M 2709 none none none none 1 N/A KXD CALLISTO-LEADING 3 COS/NUV ACQ/PEA PSA G285M 2709 none none none none 1 N/A KD CALLISTO-LEADING 4 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G CALLISTO-LEADING 5 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G CALLISTO-LEADING 6 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G CALLISTO-LEADING 7 COS/FUV TIME-TA PSA G130M 1291 none none none none 3 N/A G CALLISTO-LEADING 8 COS/FUV TIME-TA PSA G130M 1291 none none none none 3 N/A G CALLISTO-LEADING 9 COS/FUV TIME-TA PSA G130M 1291 none none none none 3 N/A G CALLISTO-LEADING 10 COS/FUV TIME-TA PSA G130M 1291 none none none none 3 N/A G CALLISTO-LEADING 11 COS/FUV TIME-TA PSA G130M 1291 none none none none 4 N/A G CALLISTO-LEADING 12 COS/FUV TIME-TA PSA G130M 1291 none none none none 4 N/A G CALLISTO-LEADING 13 COS/FUV TIME-TA PSA G130M 1291 none none none none 4 N/A G CALLISTO-LEADING 14 COS/FUV TIME-TA PSA G130M 1291 none none none none 4 N/A G 14755( 2) - 21-Jul-2016 14:40:53 - [ 10] Summary Form for Proposal 14755 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAKD, ACQ/PEAKXD, ACQ/SEARCH, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1298, BUFFER-TIME=1408, BUFFER-TIME=1712, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4, NUM-POS=7, SCAN-SIZE=3, STEP-SIZE=1.2 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GS ACQ SCENARIO BASE1B3, POS TARG 0, -0.9, POS TARG null, 5, SAME POS AS 4, SAME POS AS 9, SCHED 80% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, G285M ------------------------------------------------------------------------------------------------------------------------------------ Target Names CALLISTO-LEADING, CALLISTO-TRAILING ------------------------------------------------------------------------------------------------------------------------------------