7444( 9) - 07/28/99 10:00 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7444 Version: 9 Check-in Date: 28-Jul-1999 09:59:56 1.Proposal Title: Global Mapping of Molecular Oxygen on Ganymede ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: John Spencer Lowell Observatory CoI: Wendy Calvin United States Geological Survey, Flagstaff N CoI: Robert Johnson University of Virginia N CoI: Keith Noll Space Telescope Science Institute N CoI: John Stansberry Lowell Observatory N ------------------------------------------------------------------------------------ 5. Abstract Unique weak 5770Angstrom\ and 6275Angstrom\ absorption bands in the spectrum of Ganymede's trailing hemisphere result from the presence of condensed molecular oxygen trapped in the surface, probably resulting from bombardment of water ice by Jovian magnetospheric ions. The stability of the O_2 at Ganymede surface temperatures is surprising, and probably results from the trapping of the O_2 molecules within the ice matrix. The recent discovery that the O_2 is accompanied by O_3 helps to build a picture of a ``frozen atmosphere'' trapped in Ganymede's surface, with complex physics and chemistry. We plan to use STIS to produce a 300 km resolution global map of the strength of the O_2 bands. We will do this with scans across Ganymede's disk at three orbital longitudes. The resulting map will provide valuable constraints on the formation and stability of Ganymede's oxygen. For instance, the extent to which O_2 absorption extends onto the leading hemisphere will constrain the ratio of high energy to low energy plasma responsible for O_2 formation, and the latitude (thus, temperature) dependence of the O_2 absorption will give information on why the O_2 is stable on Ganymede. ------------------------------------------------------------------------------------ 7444( 9) - 07/28/99 10:00 - [ 2] Observations Description ------------------------ We plan to obtain scans across Ganymede at three orbital longitudes, centered near 110, 200, and 290 degrees, to build up a near-global map of O_2 distribution, taking one orbits per scan. We will use the G750L filter, as this is the only filter that will give us both the 5770 and 6275 Angstrom bands simultaneously. On each orbit we will use the 52 x 0.1'' slit to make a step- scan from limb to limb across Ganymede's 1.7'' diameter disk, with 18 slit positions in all. We will only read out the 100 spatial-dimension pixels centered on Ganymede, giving us an effective slit length of 5 arcsec. Each orbit will require a diffuse acquisition, with a CHECKBOX of 25 set to accurately find the center of Ganymede's disk. As we are scanning, we do not require a peakup. Using RPS2, we expect to be able to do a 55 second integration at each slit position. At 6 degree phase angle, R = 5.05 AU, and Delta = 4.2 AU, Ganymede's V magnitude is 4.66 (Morrison and Morrison 1977), with an angular diameter of 1.72 arcsec, giving a surface brightness of 5.58 mag / arcsec^2. The STIS exposure time calculator gives an estimated S/N of 330 per resolution element for a 55 second integration, which we can increase to a S/N 570 by threefold binning in wavelength without blurring out the O_2 bands. Our strategy will give us spectra of this quality for 220 (0.1'')^2 spots on Ganymede with every scan, and we can average spatially as necessary to trade spatial resolution for increased S/N to look for weaker features, like the 6275 Angstrom band and the weaker 5770 Angstrom band expected on the leading side. Real Time Justification ----------------------- The observations are mildly time-critical in that we require observations of Ganymede at specific longitudes, with a tolerance of about +/- 20 degrees to ensure good longitudinal overlap between scans. The observing window for each scan is about 18 hours long, recurring every 7 days during the Jupiter apparition. We will probably use the Lowell 72'' telescope to obtain groundbased disk-integrated spectra of Ganymede at the time of HST observations, at the same orbital longitudes, as a calibration check. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7444( 9) - 07/28/99 10:00 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: GANYMEDE290 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE Satellite Ganymede ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=JUPITER | STD=GANYMEDE | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | CML OF GANYMEDE FROM EARTH BETWEEN 270 | 310, RANGE GANYMEDE EARTH LT 4.4, SEP OF | JUPITER GANYMEDE FROM EARTH GT 10.0", | SEP OF IO GANYMEDE FROM EARTH GT 10", | SEP OF EUROPA GANYMEDE FROM EARTH GT | 10.0", SEP OF CALLISTO GANYMEDE FROM | EARTH GT 10.0" | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 5.58+/-0.2 | Ganymede trailing hemisphere. The | requirement of 10" minimum | separation from Jupiter and the | other satellites is added to prevent | problems with target acquisition, | and the minimum separations could be | reduced to 5" if target acquisition | is not a problem. Ganymede must not | be eclipsed by any other Galilean | satellite during the observation. | ------------------------------------------------------------------------------------------------------------------------------------ 7444( 9) - 07/28/99 10:00 - [ 4] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: GANYMEDE200 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE Satellite Ganymede ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=JUPITER | STD=GANYMEDE | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | CML OF GANYMEDE FROM EARTH BETWEEN 185 | 215, RANGE GANYMEDE EARTH LT 4.4, SEP OF | JUPITER GANYMEDE FROM EARTH GT 10.0", | SEP OF IO GANYMEDE FROM EARTH GT 10", | SEP OF EUROPA GANYMEDE FROM EARTH GT | 10.0", SEP OF CALLISTO GANYMEDE FROM | EARTH GT 10.0" | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 5.58+/-0.2 | Ganymede anti-Jupiter hemisphere. | The requirement of 10" minimum | separation from Jupiter and the | other satellites is added to prevent | problems with target acquisition, | and the minimum separations could be | reduced to 5" if target acquisition | is not a problem. Ganymede must not | be eclipsed by any other Galilean | satellite during the observation. | ------------------------------------------------------------------------------------------------------------------------------------ 7444( 9) - 07/28/99 10:00 - [ 5] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 3 | TARGET NAME: GANYMEDE110 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE Satellite Ganymede ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=JUPITER | STD=GANYMEDE | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | CML OF GANYMEDE FROM EARTH BETWEEN 90 | 130, RANGE GANYMEDE EARTH LT 4.4, SEP OF | JUPITER GANYMEDE FROM EARTH GT 10.0", | SEP OF IO GANYMEDE FROM EARTH GT 10", | SEP OF EUROPA GANYMEDE FROM EARTH GT | 10.0", SEP OF CALLISTO GANYMEDE FROM | EARTH GT 10.0" | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 5.58+/-0.2 | Ganymede leading hemisphere. The | requirement of 10" minimum | separation from Jupiter and the | other satellites is added to prevent | problems with target acquisition, | and the minimum separations could be | reduced to 5" if target acquisition | is not a problem. Ganymede must not | be eclipsed by any other Galilean | satellite during the observation. | ------------------------------------------------------------------------------------------------------------------------------------ 7444( 9) - 07/28/99 10:00 - [ 6] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GANYMEDE290 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=25, 1 0.1 S ONBOARD ACQ FOR 2 CD P DIFFUSE-CENTER=GEOMETRIC-CENTER ------------------------------------------------------------------------------------------------------------------------------------ 2 GANYMEDE290 STIS/C ACCUM 52X0.1 G750L 7751 PATTERN=PERP-TO-SLIT,NUM-POS=18, 1 61 S POS TARG -0.85, 0 CD STEP-SIZE=0.1, PATTERN-DIRECTION=PLUS, SIZEAXIS2=100,GAIN=4 ------------------------------------------------------------------------------------------------------------------------------------ 3 CCDFLAT STIS/C ACCUM 52X0.1 G750L 7751 2 25 S CD ------------------------------------------------------------------------------------------------------------------------------------ 7444( 9) - 07/28/99 10:00 - [ 7] Visit: 02 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GANYMEDE200 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=25, 1 0.1 S ONBOARD ACQ FOR 2 CD P DIFFUSE-CENTER=GEOMETRIC-CENTER ------------------------------------------------------------------------------------------------------------------------------------ 2 GANYMEDE200 STIS/C ACCUM 52X0.1 G750L 7751 PATTERN=PERP-TO-SLIT,NUM-POS=18, 1 61 S POS TARG -0.85, 0 CD STEP-SIZE=0.1, PATTERN-DIRECTION=PLUS, SIZEAXIS2=100,GAIN=4 ------------------------------------------------------------------------------------------------------------------------------------ 3 CCDFLAT STIS/C ACCUM 52X0.1 G750L 7751 2 25 S CD ------------------------------------------------------------------------------------------------------------------------------------ 7444( 9) - 07/28/99 10:00 - [ 8] Visit: 03 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GANYMEDE110 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=25, 1 0.1 S ONBOARD ACQ FOR 2 CD P DIFFUSE-CENTER=GEOMETRIC-CENTER ------------------------------------------------------------------------------------------------------------------------------------ 2 GANYMEDE110 STIS/C ACCUM 52X0.1 G750L 7751 PATTERN=PERP-TO-SLIT,NUM-POS=18, 1 61 S POS TARG -0.85, 0 CD STEP-SIZE=0.1, PATTERN-DIRECTION=PLUS, SIZEAXIS2=100,GAIN=4 ------------------------------------------------------------------------------------------------------------------------------------ 3 CCDFLAT STIS/C ACCUM 52X0.1 G750L 7751 2 25 S CD ------------------------------------------------------------------------------------------------------------------------------------ 7444( 9) - 07/28/99 10:00 - [ 9] Summary Form for Proposal 7444 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=DIFFUSE CHECKBOX=25 DIFFUSE-CENTER=GEOMETRIC-CENTER GAIN=4 SIZEAXIS2=100 PATTERN-DIRECTION=PLUS ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 POS TARG -0.85, 0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G750L ------------------------------------------------------------------------------------------------------------------------------------ Target Names GANYMEDE290 CCDFLAT GANYMEDE200 GANYMEDE110 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 7751 ------------------------------------------------------------------------------------------------------------------------------------