7939( 7) - 08/28/98 14:25 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7939 Version: 7 Check-in Date: 28-Aug-1998 13:58:51 1.Proposal Title: STIS Determination of OI Emissions from Ganymede ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GTO/STIS 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Warren Moos The Johns Hopkins University CoI: Paul Feldman The Johns Hopkins University N CoI: Doyle Hall University of Colorado N CoI: Melissa McGrath Space Telescope Science Institute N CoI: Darrell Strobel The Johns Hopkins University N CoI: Kurt Retherford The Johns Hopkins University Y ------------------------------------------------------------------------------------ 5. Abstract The STIS instrument will be used to spectroscopically image the OI emissions from Ganymede. The Galileo mission has shown that Ganymede possesses an internal magnetic field, producing a local magnetosphere within the magnetosphere of Jupiter. GHRS observation of the OI 1356 A emission shows a highly structured line which is most easily interpreted as spatially inhomogenous emissions. It is highly likely that this moon will exhibit auroral emissions analogous to Jupiter and the earth. The structure of these emissions will provide detailed insight into Ganymede's tenuous atmosphere and the magnetic field structure near it's surface. It is highly desirable that these observations be obtained in calendar 1998 in order to best support the extended Galileo mission. ------------------------------------------------------------------------------------ 7939( 7) - 08/28/98 14:25 - [ 2] Observations Description ------------------------ The Moos 1998 STIS GTO program to observe Ganymede is a 1-visit, 4-orbit program designed to measure the satellite's FUV emissions. Visit 1 will observe Ganymede near western elongation using 4 HST orbits: a DIFFUSE acquisition (no peakup required), 2 orbits of MAMA G140L 52X2 TIME-TAG spectroscopy, followed by 2 orbits of MAMA G140M TIME-TAG spectroscopy in the OI 1356A/1359A emission doublet. We request that the observations be scheduled between 29-Jul-1998 and 4-Nov-1998 to minimize terrestrial airglow and geocoronal Lyman alpha line emission contamination. However, if HST/Io scheduling constraints make this request difficult, the scheduling window may be extended as necessary. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7939( 7) - 08/28/98 14:25 - [ 3] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: GANYMEDE-WEST ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE GANYMEDE ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=JUPITER | STD=GANYMEDE | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | OLG OF GANYMEDE BETWEEN 235 305, OLG OF | JUPITER BETWEEN 317 42 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 4.6+/-0.2 | Ganymede is at elongation on B-V = 0.83 | Jupiter's west (dusk) side. The | other galilean satellites must be | separated by more than 10 arcsec | from the target (by default). Here | we have made the Ganymede orbital | longitude (OLG) window centered at | the elongation point +/- 35 degrees, | but this range could be adjusted | slightly to ease scheduling. | ------------------------------------------------------------------------------------------------------------------------------------ 7939( 7) - 08/28/98 14:25 - [ 4] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Visit 1 must observe Ganymede west of Jupiter in the period specified near Jupiter opposition (16-Sep-1998). This ensures that the duration of each orbit's SHADOW interval is near its maximum for Jupiter observations, minimizing terrestrial airglow and geocoronal Lyman alpha line emission contamination. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 GANYMEDE-WE STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE, 1 0.1 S ONBOARD ACQ FOR 11, 12, ST CD P DIFFUSE-CENTER=GEOMETRIC-CENTER, 13, 14, 15, 16, 17, 18 CHECKBOX=37 Comments: In the requested observation window Ganymede is a V=4.4 solar-type source whose disk projects a diameter between 1.69 and 1.84 arcsec. A DIFFUSE ACQ with CHECKBOX=37 (1.88 arcsec) with no PEAK-UP is an appropriate choice for these observations that use the 52X2 slit. A previous acquisition of Io (V=5.0) using the F28X50LP filter and performed when it's apparent diameter was 1.16 arcsec, produced a maximum 1.1e4 DN/px for a 0.1 second CCD exposure using the default GAIN of 4. Compared to Io, Ganymede's brighter apparent visual magnitude leads to an increase of flux that's 1.74 times greater. We therefore expect a maximum 1.9e4 DN/px for a 0.1 second CCD exposure of Ganymede in a similar type of acquistion. This is roughly a factor of two smaller than the CCD saturation limit of 3.6e4 DN/px. During the CCD exposure centered on Ganymede we expect 1.2e7 DN to be accumulated within the brightest checkbox, providing an adequate signal-to-noise ratio for DIFFUSE acquisitions. ------------------------------------------------------------------------------------------------------------------------------------ 11 GANYMEDE-WE STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=1700 1 850 S ST UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 12 GANYMEDE-WE STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=1700 1 850 S ST UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 13 GANYMEDE-WE STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=1700 1 1205 S ST UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 7939( 7) - 08/28/98 14:25 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 14 GANYMEDE-WE STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=1700 1 1205 S ST UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 15 GANYMEDE-WE STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=4000 1 1125 S ST UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 16 GANYMEDE-WE STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=4000 1 1100 S ST UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 17 GANYMEDE-WE STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=4000 1 1200 S ST UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 18 GANYMEDE-WE STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=4000 1 1130 S ST UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 7939( 7) - 08/28/98 14:25 - [ 6] Summary Form for Proposal 7939 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=DIFFUSE DIFFUSE-CENTER=GEOMETRIC-CENTER CHECKBOX=37 BUFFER-TIME=1700 BUFFER-TIME=4000 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GTO/STIS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 11, 12, 13, 14, 15, 16, 17, 18 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names GANYMEDE-WEST ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------