7792( 5) - 05/14/98 14:02 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7792 Version: 5 Check-in Date: 14-May-1998 13:52:58 1.Proposal Title: HST SUPPORT FOR MARS GLOBAL SURVEYOR ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO/DD 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: PHILIP B. JAMES UNIVERSITY OF TOLEDO CoI: Todd Clancy Space Science Institute N CoI: Steve Lee LASP, University of Colorado N CoI: Jim Bell Cornell University N CoI: Michael Wolff University of Toledo N ------------------------------------------------------------------------------------ 5. Abstract The observations included in this proposal have the goal of providing data to support Mars Global Surveyor during aero- braking by monitoring dust opacity on the planet. ------------------------------------------------------------------------------------ 7792( 5) - 05/14/98 14:02 - [ 2] Observations Description ------------------------ The ability of HST to observe Mars from the ultraviolet portion of the spectrum to the near infrared allows determination of the amounts of condensates and dust in the Martian atmosphere. For example, in the UV essentially all of the reflected intensity results from atmospheric scattering because absorption by Fe+3 minerals results in negligible surface albedo. The effects of dust and condensates on the observed surface reflectance can be modeled via a radiative transfer program to provide quantitative estimates of optical depths (James et al., 1994). During Cycle 5 we observed regional dust in Utopia at Ls = 82( and in multiple locations at Ls=140( (Figure 2)(Wolff et al., 1996). We observed several local dust clouds during Cycle 6 including a significant dust storm in the Valles Marineris canyon system just before the Pathfinder landing. In addition, many of our images have included condensate clouds. Our experience with WFPC2 images during these previous cycles gi ves us confidence that we can dete rmine the amounts of dust and condensate clouds in the Martian atmosphere using a relatively small set of filters: 410M, 502N, 673N, and 1042M. The observations included in this proposal will augment visits currently scheduled in our Cycle 7 Proposal (GO 7276) for the sole purpose of supporting the Mars Global Surveyor Mission (MGS) which will be in the aerobraking phase of the mission shortly after orbital insertion on September 12. On September 12 MGS will arrive at Mars and, following a brief burn, will be left in a high eccentricity orbit with apoapsis of 56, 000 km and periapsis of 300 kilometers. The orbit must be modified into a circular orbit of radius 380 kilometers. This will be accomplished by aerobraking, which commences on September 21. The closest approach to Mars is actually within the outer fringes of the atmosphere. Kinetic energy is removed at each periapsis passage, thus lowering the apoapsis of the orbit. The process is very sensitive to the density of the atmosphere at periapsis: if the density is too low, the orbit will not evolve properly; and, if it is too high, the spacecraft could b e damaged by air resistance. The density at high altitudes is very sensitive to the amount of dust in the atmosphere because dust causes absorption of insolation and heating in the atmosphere which translates into expansion at high altitudes. For example, the atmospheric density found by Pathfinder was a factor of five lower than that expected on the basis of the Viking descent profile. What makes the process especially risky is the fact that the autumnal equinox on Mars occurs on September 12; the spring season in the southern hemisphere is typically the dustiest period on Mars and is the time when the great planet encircling dust storms have been observed in the past. Such a storm could have a drastic effect on aerobraking. For this reason, all scientific efforts which are capable of monitoring dust on Mars will be used to provide input to the MGS controllers as they plan aerobraking maneuvers. The frequency of observations is especially crucial because of the very rapid expansion of global storms; the 1977a storm observed by Viking expanded from a local dust cloud to cover the entire southern hemisphere in only two days Real Time Justification ----------------------- We have some observations scheduled as part of our program 7276 during the crucial period between September 15 and October 15, when we can no longer observe Mars due to the minimum solar elongation constraint. We propose to schedule six additional one orbit visits during this period timed in such a way as to provide input on the occurrence of observable dust clouds as well as on the variation of the background dust opacity on the planet. These visits will consist only of WFPC2 exposures using the filters listed above, and our experience shows that they can be done inside SAA contour 05 (but not 02) if necessary. The observations will be prepared using the SCHED 100% special requirement, so there should be no orbital visibility limits on scheduling. The observations will not have the strong central meridian constraint that we have normally applied in order to study specific regions because we are mainly interested in only global opacity in mid latitudes (periapsis remain s between 20( and 25( N during thi s four week period while the sub earth latitude decreases from 15( to 6() so there should be minimal problems scheduling this from the moving target point of view. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7792( 5) - 05/14/98 14:02 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7792( 5) - 05/14/98 14:02 - [ 4] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: MARS-MGS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET mars ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=MARS | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 4.0+/-0.1 | SURF(4100)=2.4+/-0.2e-11 | SURF(5020)=6.3+/-0.2e-11 | SURF(6730)=1.1+/-0.2e-10 | | ------------------------------------------------------------------------------------------------------------------------------------ 7792( 5) - 05/14/98 14:02 - [ 5] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 12-Sep-1997 AND 13-Sep-1997 SCHED 100% On Hold Comments: Additional Comments: SAA contour 05 (but not 02) OK. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 MARS-MGS WFPC2 IMAGE PC1-FIX F410M 1 1.8 S ------------------------------------------------------------------------------------------------------------------------------------ 11 MARS-MGS WFPC2 IMAGE PC1-FIX F502N 1 4.0 S ------------------------------------------------------------------------------------------------------------------------------------ 12 MARS-MGS WFPC2 IMAGE PC1-FIX F673N 1 0.5 S ------------------------------------------------------------------------------------------------------------------------------------ 13 MARS-MGS WFPC2 IMAGE PC1-FIX F1042M 1 2.6 S ------------------------------------------------------------------------------------------------------------------------------------ 7792( 5) - 05/14/98 14:02 - [ 6] Visit: 02 Visit Priority: Visit Requirements: BETWEEN 23-Sep-1997 AND 24-Sep-1997 SCHED 100% On Hold Comments: Additional Comments: SAA contour 05 is OK. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 20 MARS-MGS WFPC2 IMAGE PC1-FIX F410M 1 1.8 S ------------------------------------------------------------------------------------------------------------------------------------ 21 MARS-MGS WFPC2 IMAGE PC1-FIX F502N 1 4.0 S ------------------------------------------------------------------------------------------------------------------------------------ 22 MARS-MGS WFPC2 IMAGE PC1-FIX F673N 1 0.5 S ------------------------------------------------------------------------------------------------------------------------------------ 23 MARS-MGS WFPC2 IMAGE PC1-FIX F1042M 1 2.6 S ------------------------------------------------------------------------------------------------------------------------------------ 7792( 5) - 05/14/98 14:02 - [ 7] Visit: 03 Visit Priority: Visit Requirements: BETWEEN 26-Sep-1997 AND 27-Sep-1997 SCHED 100% On Hold Comments: Additional Comments: SAA contour 05 (but not 02) OK. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 30 MARS-MGS WFPC2 IMAGE PC1-FIX F410M 1 1.8 S ------------------------------------------------------------------------------------------------------------------------------------ 31 MARS-MGS WFPC2 IMAGE PC1-FIX F502N 1 4.0 S ------------------------------------------------------------------------------------------------------------------------------------ 32 MARS-MGS WFPC2 IMAGE PC1-FIX F673N 1 0.5 S ------------------------------------------------------------------------------------------------------------------------------------ 33 MARS-MGS WFPC2 IMAGE PC1-FIX F1042M 1 2.6 S ------------------------------------------------------------------------------------------------------------------------------------ 7792( 5) - 05/14/98 14:02 - [ 8] Visit: 04 Visit Priority: Visit Requirements: BETWEEN 05-Oct-1997 AND 06-Oct-1997 SCHED 100% On Hold Comments: Additional Comments: SAA contour 05 (but not 02) OK. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 40 MARS-MGS WFPC2 IMAGE PC1-FIX F410M 1 1.8 S ------------------------------------------------------------------------------------------------------------------------------------ 41 MARS-MGS WFPC2 IMAGE PC1-FIX F502N 1 4.0 S ------------------------------------------------------------------------------------------------------------------------------------ 42 MARS-MGS WFPC2 IMAGE PC1-FIX F673N 1 0.5 S ------------------------------------------------------------------------------------------------------------------------------------ 43 MARS-MGS WFPC2 IMAGE PC1-FIX F1042M 1 2.6 S ------------------------------------------------------------------------------------------------------------------------------------ 7792( 5) - 05/14/98 14:02 - [ 9] Visit: 05 Visit Priority: Visit Requirements: BETWEEN 09-Oct-1997 AND 10-Oct-1997 SCHED 100% On Hold Comments: Additional Comments: SAA contour 05 (but not 02) OK. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 50 MARS-MGS WFPC2 IMAGE PC1-FIX F410M 1 1.8 S ------------------------------------------------------------------------------------------------------------------------------------ 51 MARS-MGS WFPC2 IMAGE PC1-FIX F502N 1 4.0 S ------------------------------------------------------------------------------------------------------------------------------------ 52 MARS-MGS WFPC2 IMAGE PC1-FIX F673N 1 0.5 S ------------------------------------------------------------------------------------------------------------------------------------ 53 MARS-MGS WFPC2 IMAGE PC1-FIX F1042M 1 2.6 S ------------------------------------------------------------------------------------------------------------------------------------ 7792( 5) - 05/14/98 14:02 - [ 10] Visit: 06 Visit Priority: Visit Requirements: BETWEEN 12-Oct-1997 AND 14-Oct-1997 SCHED 100% On Hold Comments: Additional Comments: SAA contour 05 (but not 02) OK. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 60 MARS-MGS WFPC2 IMAGE PC1-FIX F410M 1 1.8 S ------------------------------------------------------------------------------------------------------------------------------------ 61 MARS-MGS WFPC2 IMAGE PC1-FIX F502N 1 4.0 S ------------------------------------------------------------------------------------------------------------------------------------ 62 MARS-MGS WFPC2 IMAGE PC1-FIX F673N 1 0.5 S ------------------------------------------------------------------------------------------------------------------------------------ 63 MARS-MGS WFPC2 IMAGE PC1-FIX F1042M 1 2.6 S ------------------------------------------------------------------------------------------------------------------------------------ 7792( 5) - 05/14/98 14:02 - [ 11] Summary Form for Proposal 7792 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/DD ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 12-Sep-1997 AND 13-Sep-1997 SCHED 100% BETWEEN 23-Sep-1997 AND 24-Sep-1997 SCHED 100% BETWEEN 26-Sep-1997 AND 27-Sep-1997 SCHED 100% BETWEEN 05-Oct-1997 AND 06-Oct-1997 SCHED 100% BETWEEN 09-Oct-1997 AND 10-Oct-1997 SCHED 100% BETWEEN 12-Oct-1997 AND 14-Oct-1997 SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F410M F502N F673N F1042M ------------------------------------------------------------------------------------------------------------------------------------ Target Names MARS-MGS ------------------------------------------------------------------------------------------------------------------------------------