11186( 4) - 21-May-2008 16:51:35 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11186 Version: 4 Check-in Time: 21-May-2008 16:51:35 STScI Edit Number: 2 Title Investigation of the spatial and temporal structure of Europa's atmospheric emissisons ------------------------------------------------------------------------------------ Type Cycle Parallel Pointing Tolerance GO 16 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Joachim Saur Universitat zu Koeln CoI: Prof. Paul D. Feldman The Johns Hopkins University N CoI: Prof. Darrell F. Strobel The Johns Hopkins University N CoI: Dr. Kurt D. Retherford Southwest Research Institute N CoI: Prof. Jean-Claude M. Gerard Universite de Liege N CoI: Dr. Denis Grodent Universite de Liege N CoI: Dr. Nico Schilling Universitat zu Koeln N ------------------------------------------------------------------------------------ Abstract We propose to explore the spatial structure and temporal variability of Europa's O2 atmosphere with ACS/SBC. Previous HST images display non-uniform UV emission from Europa's atmosphere, which maximizes within the disk of Europa on its anti-Jovian northern quadrant. These images were taken at western elongation and are not conclusive, but bring up the exciting question whether the non-uniform emission is due to a locally enhanced neutral atmosphere. A locally inhomogeneous atmosphere would imply locally modified surface properties. This might provide clues on inhomogeneities of the underlying ice structure and thus properties of a potential subsurface ocean. Since the inhomogeneous emission comes from within the disk of Europa, we propose to study Europa at eastern and western elongation to decide if the locally enhanced emission is truly an atmospheric effect. We propose to take for each elongation five contiguous observations within one rotation period of Jupiter to discriminate between a competing effect that produces inhomogeneous emission patterns, i.e., the electrodynamic interaction with Jupiter's magnetosphere. We will use ACS/SBC with PR130L prism to completely separate the two prominent FUV oxygen lines OI 1304 A and OI 1356 A emitted from Europa's atmosphere. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to use ACS/SBC with prism PR130L to investigate the spatial structure of Europa's atmosphere. With this prism we will eliminate contributions from the long wavelength end of the SBC bandpass due to reflected sun light on Europa's surface by spectrally dispersing the image. We will be able to separate the two prominent FUV oxygen lines OI 1304 A and OI 1356 A emitted from Europa's atmosphere. We propose to center the disk of Europa (maximum diameter ~ 1.2") to obtain a symmetric field of view around the disk of Europa. We are requesting five contiguous orbits at eastern elongation, i.e., for the leading/downstream (longitude 90 degrees) hemisphere of Europa. The western elongation has been previously observed by STIS in cycle 8. Five orbits span more than one half of a Jovian rotation, so that a significant change of the orientation of Jupiter's magnetic field relative to Europa occurs over the course of the observations. This will allow us to test the dependence 11186( 4) - 21-May-2008 16:51:35 - [ 2] of the observed emission morphology on the magnetic field orientation. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 11186( 4) - 21-May-2008 16:51:35 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: EUROPA-EAST ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE Jovian satellite ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=JUPITER STD=EUROPA ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS OLG OF JUPITER BETWEEN 330.0 30.0, OLG OF EUROPA-EAST BETWEEN 70.0 110.0, SEP OF GANYMEDE EUROPA FROM EARTH GT 5" ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 5.3 +/- 0.5 Ephemeris Center: EARTH ------------------------------------------------------------------------------------------------------------------------------------ 11186( 4) - 21-May-2008 16:51:35 - [ 4] Visit: 01 Visit Priority: Visit Requirements: 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 EUROPA-EAST ACS/SBC ACCUM SBC PR130L 20 600.0 S see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 1 none 1 641.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 2 none 1 641.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 3 none 1 641.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 4 none 1 641.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 5 none 2 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 6 none 2 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 7 none 2 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 8 none 2 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 9 none 3 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 10 none 3 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 11 none 3 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 12 none 3 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 13 none 4 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 14 none 4 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 15 none 4 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 16 none 4 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 17 none 5 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 18 none 5 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 19 none 5 652.0 S EUROPA-EAST 1 ACS/SBC ACCUM SBC PR130L none none 20 none 5 652.0 S 11186( 4) - 21-May-2008 16:51:35 - [ 5] Summary Form for Proposal 11186 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures SBC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/SBC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements PR130L ------------------------------------------------------------------------------------------------------------------------------------ Target Names EUROPA-EAST ------------------------------------------------------------------------------------------------------------------------------------