6008( 21) - 05/31/96 22:33 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6008 Version: 21 Check-in Date: 31-May-1996 22:27:47 1.Proposal Title: The Atmosphere of Io and its Interaction with the Plasma Torus ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Solar System GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Gilda Ballester University of Michigan CoI: John Clarke University of Michigan N CoI: Joe Ajello Jet Propulsion Laboratory N CoI: Darrell Strobel Johns Hopkins University N CoI: Nick Schneider University of Colorado N CoI: Melissa McGrath Space Telescope Science Institute N CoI: Mike Combi University of Michigan N ------------------------------------------------------------------------------------ 6. Abstract Post-COSTAR GHRS spectra of Io's O and S emission are of excellent quality. Spatial scans and new eclipse observations show that the emissions are dependent on the plasma torus and may change on short time scales. Far-UV WFPC2 images of Io have now shown these emissions to have an irregular morphology. Strong far-UV emissions from Jupiter associated with the foot of the Io flux tube have also been seen in WFPC2 images, and the associated processes could be related to the excitation of Io's O and S emissions. We need to characterize the temporal changes of the Io emissions to understand the interaction of the atmosphere with the torus (and Jupiter). We will make GHRS G140L observations of Io over 6 consecutive HST orbits encompassing half a torus rotation with respect to Io. These data will be obtained in mid-1996 in coordination with Galileo UVS observations of Io. We will also dedicate 2 orbits to observe Io as it goes into eclipse, and 3 more orbits as it comes out of eclipse in order to characterize the temporal changes in the emissions related to sunlight. These observations cannot be made in coordination with Galileo, and have to be made in separate visits. The GHRS exposures will use the 1.74 arcsec aperture and the G140L grating centered at 1370 and 1790 Angstroms (A) to detect various S and O multiplets. (The acquisition orbits with GHRS side 2 will be optimized with medium resolution spectra at 1479 and 1251 A to resolve various S and S+ multiplets.) ------------------------------------------------------------------------------------ 6008( 21) - 05/31/96 22:33 - [ 2] Observations Description ------------------------ Three visits will be made for a total of 11 HST orbits. Chronologically: 1) This visit will consist of 3 consecutive orbits dedicated to observing O and S emissions from Io's atmosphere with the GHRS as Io comes out of eclipse. These observations must be made post-opposition, best during ~ 1 Aug - 30 Sep 1995. The next opportunity would be well within Cycle 6, during the period ~ 7 Sep - 1 Nov 1996. The first orbit will include the guide star acquisition, acquisition of another Galilean satellite with GHRS side 2 and the slew to Io. During Earth occultation we will switch from side 2 to side 1. In the second orbit we will observe Io as it comes out of eclipse, taking consecutive G140L spectra centered at 1370 A with 0.5 min integration time. Similar consecutive spectra will be taken in the third orbit. 2) This visit is the main part of the program, and will consist of 6 consecutive orbits dedicated to measure the short-term variability of the O and S emissions from Io's atmosphere simultaneous with observations with the Galileo spacecraft. This 6-orbit sequence should be made on 3 July 1996 overlapping the period 06:45 - 10:52 UT when the Galileo UVS will be making spatial scans of Io. At this time Io will be visible from Earth, having passed eastern elongation and approaching inferior conjunction with Jupiter. (As of Feb 1995, the Galileo schedule seems final, but any unforeseen changes will be informed to STScI ahead of time). In case this observing time is absolutely unfeasible (eg, due to SAA problems), we could observe the closest possible in time to this period. Galileo will make another study of Io while it is eclipsed by Jupiter around 1 Jul 1996 00:00 UT, but HST will not be able to observe this eclipse from Earth since the Jovian system will be near opposition. If needed, we could observe immediately before or after this Galileo eclipse observation, before ~20:30 UT 30 Jun 1996 or after ~02:00 UT 1 Jul 1996. The first orbit will consist of the acquisition of Io with GHRS side 2 and G160M spectra centered at 1254 A (to resolve the S and S+ emissions). In the following orbits we will take consecutive (side 1) G140L spectra centered at 1370 A with 0.5 min integration time for a period of 9 to 26 min, plus an additional integration with the grating centered at 1790 A to detect additional S multiplets. Instead of requesting dark time, since the observations will be near opposition, we ask that information of the dark time window is provided to determine the contamination from Earth in the O 1304 A emission. 3) This third visit will consist of 2 consecutive orbits to observe the O and S emissions as Io goes into eclipse. These observations need to be made pre-opposition, which in Cycle 5 can only be done around 6 Mar - 5 May 1996. The first orbit will include the guide star acquisition, on-board acquisition of Io and an exposure with GHRS side 2, using the G160M centered at 1479 A. In the second orbit we will take consecutive (side 1) G140L GHRS spectra of 0.5 min integration time, centered at 1370 A, as Io goes into and during eclipse. Real Time Justification ----------------------- The 6-orbit sequence in coordination with Galileo observations of Io is one of the primary goals of the program. Out of the possible opportunities to coordinate with Galileo, the 3 Jul 1996 from 06:45 to 10:52 UT is the only time we can make simultaneous HST and Galileo observations of Io. Any update on the Galileo scheduling will be known ahead of time (co-I J. Ajello is in the Galileo UVS team). In case it turns out to be impossible to exactly overlap the observations, two possible alternatives have been provided, but please consult us in this case. The periods requested for the Io eclipse observations will provide the adequate separation of Io from Jupiter to be observable with HST while in eclipse. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6008( 21) - 05/31/96 22:33 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6008( 21) - 05/31/96 22:33 - [ 4] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: IO-EGRESS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE IO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=JUPITER | STD=IO | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | OLG OF JUPITER BETWEEN 240 290 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 5.0+/-0.5 | SIZE=1.0+/-.2 | F-LINE(1304)=2.1+/-1e-13 | W-LINE(1304)=0.01 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: IO-ACQ-EGRESS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: OFFSET EUROPA ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=JUPITER | STD=EUROPA | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 5.3+/-0.5 | Acquisition for Io while in shadow SIZE=2.0+/-.2 | for the egress observations. The SURF-CONT(2700)=2+/-1e-13 | strategy is to acquire Europa or | Ganymede and then blind offset to | Io, both in the 2 arcsec GHRS | aperture. | ------------------------------------------------------------------------------------------------------------------------------------ 6008( 21) - 05/31/96 22:33 - [ 5] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 3 | TARGET NAME: IO-UVS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE IO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=JUPITER | STD=IO | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | OLG OF JUPITER BETWEEN 345 15 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 5.0+/-0.5 | SIZE=1.0+/-.2 | F-LINE(1304)=2.1+/-1e-13 | W-LINE(1304)=0.01 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 4 | TARGET NAME: IO-INGRESS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE IO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=JUPITER | STD=IO | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | OLG OF JUPITER BETWEEN 70 120 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 5.0+/-0.5 | SIZE=1.0+/-.2 | F-LINE(1304)=2.1+/-1e-13 | W-LINE(1304)=0.01 | | ------------------------------------------------------------------------------------------------------------------------------------ 6008( 21) - 05/31/96 22:33 - [ 6] Visit: 01 Visit Requirements: BETWEEN 09-Aug-1995 AND 28-Sep-1995 On Hold Comments: Additional Comments: Three consecutive orbits with GHRS to observe Io as it comes out of eclipse. Observations are possible during the post-opposition window provided for 1995. The next opportunity in 1996 is in cycle 6: BETWEEN 07- SEP-96 AND 01-NOV-96. In the 2nd orbit Io should be observed for at least ~15 min before emergence from eclipse, and at least ~15 min in sunlight. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 111 IO-ACQ-EGRE HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=5,LOCATE=EXTENDED 1 10 S ONBOARD ACQ FOR 112-132 SS NO SPLIT Comments: STEP-TIME = 0.2S On-board acquisition of Europa or Ganymede to offset to Io. ------------------------------------------------------------------------------------------------------------------------------------ 112 IO-ACQ-EGRE HRS IMAGE 2.0 MIRROR-N2 1 51.2 S END ORBIT NO SPLIT SS Comments: Image of Europa in LSA for pointing information. Estimated counts/dwell_point = 100. Offset to Io after this exposure. ------------------------------------------------------------------------------------------------------------------------------------ 121 IO-EGRESS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1 32 0.5 M NO SPLIT Comments: Exposures 121 and 122 should together cover Io about half the time when in shadow and the other half in sunlight. ------------------------------------------------------------------------------------------------------------------------------------ 122 IO-EGRESS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1 31 0.5 M END ORBIT NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 131 IO-EGRESS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1 32 0.5 M NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 132 IO-EGRESS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1 26 0.5 M END ORBIT NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 6008( 21) - 05/31/96 22:33 - [ 7] Visit: 02 Visit Requirements: BETWEEN 26-Jun-1996:02:00:00.0 AND 26-Jun-1996:03:00:00.0 ORIENT 272D TO 272D On Hold Comments: Additional Comments: Six consecutive orbits with GHRS, on 26-JUL-96 overlapping the period 08:49 - 11:20 UT of the Galileo UVS Io-scan observations. In case this scheduling is really impossible, two alternative windows are provided below to make observations immediately before or after Galileo Io eclipse observations: BETWEEN 23-JUN-96:02:45 AND 23-JUN-96:19:15 and BETWEEN 24-JUN-96:00:00 AND 24-JUN-96:16:30, respectively. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 211 IO-UVS HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=5,LOCATE=EXTENDED 1 10 S ONBOARD ACQ FOR 212-262 SEQ 211-213 NON-INT Comments: STEP-TIME = 0.4S On-board acquisition of Io with GHRS. ------------------------------------------------------------------------------------------------------------------------------------ 212 IO-UVS HRS IMAGE 2.0 MIRROR-N2 1 102.4 S Comments: Image of Io in LSA for pointing information. Estimated counts/dwell_point = 100. ------------------------------------------------------------------------------------------------------------------------------------ 213 IO-UVS HRS ACCUM 2.0 G160M 1254. STEP-PATT=1 2 6.4 M Comments: Exposure of Io with side 2. ------------------------------------------------------------------------------------------------------------------------------------ 221 IO-UVS HRS ACCUM 2.0 G140L 1790. STEP-PATT=1 5 4.0 M SEQ 221-222 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 222 IO-UVS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1 28 29.6 S ------------------------------------------------------------------------------------------------------------------------------------ 231 IO-UVS HRS ACCUM 2.0 G140L 1790. STEP-PATT=1 5 4.0 M SEQ 231-232 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 232 IO-UVS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1, 28 29.6 S SAA-CONTOUR=HIGH-NOISE ------------------------------------------------------------------------------------------------------------------------------------ 241 IO-UVS HRS ACCUM 2.0 G140L 1790. STEP-PATT=1 1 6.0 M SEQ 241-243 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 242 IO-UVS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1, 23 29.6 S SAA-CONTOUR=HIGH-NOISE ------------------------------------------------------------------------------------------------------------------------------------ 243 IO-UVS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1, 12 29.6 S SAA-CONTOUR=HIGH-NOISE ------------------------------------------------------------------------------------------------------------------------------------ 251 IO-UVS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1, 25 29.6 S SEQ 251-252 NON-INT SAA-CONTOUR=HIGH-NOISE ------------------------------------------------------------------------------------------------------------------------------------ 252 IO-UVS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1, 26 29.6 S SAA-CONTOUR=HIGH-NOISE ------------------------------------------------------------------------------------------------------------------------------------ 261 IO-UVS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1, 28 29.6 S SEQ 261-262 NON-INT SAA-CONTOUR=HIGH-NOISE ------------------------------------------------------------------------------------------------------------------------------------ 262 IO-UVS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1, 28 29.6 S SAA-CONTOUR=HIGH-NOISE ------------------------------------------------------------------------------------------------------------------------------------ 6008( 21) - 05/31/96 22:33 - [ 8] Visit: 03 Visit Requirements: BETWEEN 06-Mar-1996 AND 25-Apr-1996 On Hold Comments: Additional Comments: Two consecutive orbits with GHRS as Io goes into eclipse. Observations are possible during the given 1996 pre-opposition window. In the 2nd orbit Io should be observed for at least ~15 min before passing into Jupiter shadow, and at least ~15 min in shadow. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 311 IO-INGRESS HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=5,LOCATE=EXTENDED 1 10 S ONBOARD ACQ FOR 312-322 NO SPLIT Comments: STEP-TIME = 0.4S On-board acquisition of Io with GHRS. ------------------------------------------------------------------------------------------------------------------------------------ 312 IO-INGRESS HRS IMAGE 2.0 MIRROR-N2 1 102.4 S NO SPLIT Comments: Image of Io in LSA for pointing information. Estimated counts/dwell_point = 100. ------------------------------------------------------------------------------------------------------------------------------------ 313 IO-INGRESS HRS ACCUM 2.0 G160M 1479. STEP-PATT=1 4 209.6 S NO SPLIT Comments: Exposure of Io with side 2. ------------------------------------------------------------------------------------------------------------------------------------ 321 IO-INGRESS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1 32 29.6 S NO SPLIT Comments: Exposures 321 and 322 should together cover Io about half the time when in sunlight and the other half in shadow. ------------------------------------------------------------------------------------------------------------------------------------ 322 IO-INGRESS HRS ACCUM 2.0 G140L 1370. STEP-PATT=1 31 29.6 S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 6008( 21) - 05/31/96 22:33 - [ 9] Summary Form for Proposal 6008 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ IMAGE ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=5 LOCATE=EXTENDED STEP-PATT=1 SAA-CONTOUR=HIGH-NOISE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Solar System ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 09-Aug-1995 AND 28-Sep-1995 ONBOARD ACQ FOR 112-132 NO SPLIT END ORBIT NO SPLIT BETWEEN 26-Jun-1996 02 00 00.0 AND 26-Jun-1996 03 00 00.0 ORIENT 272D TO 272D ONBOARD ACQ FOR 212-262 SEQ 211-213 NON-INT SEQ 221-222 NON-INT SEQ 231-232 NON-INT SEQ 241-243 NON-INT SEQ 251-252 NON-INT SEQ 261-262 NON-INT BETWEEN 06-Mar-1996 AND 25-Apr-1996 ONBOARD ACQ FOR 312-322 NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G140L G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names IO-ACQ-EGRESS IO-EGRESS IO-UVS IO-INGRESS ------------------------------------------------------------------------------------------------------------------------------------