Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5489 Report Date: 18-Jul-95:17:31 Version: ********** Check-in Date: ********** 1.Proposal Title: MULTI-SPECTRAL IMAGES OF VESTA: CYCLE 4 MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID SOLAR SYSTEM GO Sub Category MINOR PLANETS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Benjamin H. Zellner COMPUTER SCIENCES CORPORATIO USA 410-338-4729 ------------------------------------------------------------------------------------ 7. Abstract Asteroid 4 Vesta is one of two solar system bodies beyond the terrestrial planets known to have a highly variegated surface resulting from surface lava flows. Unlike Io, Vesta's surface remains insufficiently resolved for the purpose of geologic mapping. We propose to use the Planetary Camera of the WFPC2 for global imaging of asteroid 4 Vesta in late 1994. At that geocentric distance, we expect to resolve more than 140 pixels covering 96% of Vesta's surface. Images during eight HST orbits are requested for good spatial coverage of the rotating planet. Four filter passbands ranging from 0.44 to 1.04 microns wavelength are chosen to provide mineralogical diagnosticity and to maximize the expected albedo contrast. Interpretative techniques are described which will lead to recognition and mapping of pyroxene/feldspar domains indicative of surface lava flows and olivine-rich regions exposed by impact of geologic units originally below Vesta's basaltic crust. Also we anticipate that this program will greatly enhance the interpretability of a small number of monochromatic images of Vesta to be obtained at the highest possible pixel resolution by the FOC GTO team. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 0 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5489 PI: Benjamin H. Zellner Proposal Title: MULTI-SPECTRAL IMAGES OF VESTA: CYCLE 4 MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Benjamin H. Zellner 1780 USA Eddie N. Wells 1780 USA Alex Storrs 3470 USA Richard P. Binzel 2630 USA Michael Gaffey 3220 USA Rudolph Albrecht 5555 GERMANY X Peter Thomas 1810 USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. We want to image asteroid 4 Vesta with the Planetary Camera of the WFPC2 near its December 1994 opposition. We would prefer that the solar phase angle be less than 12 degrees (15 degrees OK) but larger than 2 degrees. We are using a standard sequence of 7 short exposures in four filters that should be made contiguously and in a single orbit of HST. Note Science Tape Recorder management may present a problem; we would be happy to have PC1 only read out, but there appears to be no way for the GO to specify that. We want the sequence to be run 8 times, to map Vesta at about 45-degree intervals in the longitude of its central meridian. (Its rotation period is 5.34213 hours.) The eight longitudes can be be imaged in any order, but should all be done within a two-week period to minimize aspect changes. It would be most efficient (but not necessary) for all the observations to be taken in eight consecutive orbits of HST. We request fine lock with a guiding tolerance of 0.02 arcsec during the longest (20 seconds) exposures. Actually gyro tracking might suffice and can be discussed if necessary. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Groundbased speckle imaging of Vesta has succeeded only in showing large but poorly defined regions of differing albedo. Imaging with sufficient resolution for geological interpretations in mineralogically diagnostic wavelength bands can only be done with HST or rendezvous spacecraft. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. As noted above we want to get Vesta between 2 and 12 degrees solar phase angle, and at eight different rotational aspects, more or less equally spaced in longitude. We have used the PHASE requirement in the exposure logsheet, but the same results could be accomplished in other ways. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. No special calibrations are required. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. None. ------------------------------------------------------------------------------------ 9. Description of previous HST work. See Phase 1 proposal. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). See Phase 1 proposal. ------------------------------------------------------------------------------------ 11. Address Information Page 3 Name: BENJAMIN H. ZELLNER Category: PI Institution: 1780 Address: City: State: Zip Code: Country: Telephone: 410-338-4729 Telex (or e-mail): zellner@stsci.edu ------------------------------------------------------------------------------------ Name: Category: CON Institution: Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 5489 [ 4] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: VESTA ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID 4 ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = 4(VESTA) | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | SEP OF SUN EARTH FROM VESTA GT 2 D | SEP OF SUN EARTH FROM VESTA LT 12 D | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |V = 6.9 +/- 0.2 | ASTEROID 4 VESTA, SOLAR PHASE ANGLE 2 |SIZE = 0.43 +/- 0.02 | > 2 DEG BUT < 12 DEGREES. OPPOSITION | | IS 26 DEC 1994. | ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5489 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 DEFINE VESTA WFPC2 IMAGE PC1 F673N 6732 1 2.0 S 100 1 1 CYCLE 4 VESTA- 2.0 S SEQ 1-7 NON-INT SEQ PCS MODE F / 1-7 PERIOD 5.34213H +/ - 0.00001H ZERO-PHASE 25-DEC- Comments: FIRST OF SEVEN EXPOSURES TO BE 1994 +/- 0D MADE IN ONE ORBIT; REPEAT 8 TIMES TO GET COMPLETE LONGITUDE COVERAGE OF ROTATING ASTEROID. ZERO-PHASE EPOCH IS ARBITRARY. ------------------------------------------------------------------------------------------------------------------------------------ 2 DEFINE VESTA WFPC2 IMAGE PC1 F953N 9534 1 20.0 S 100 1 1 CYCLE 4 VESTA- 20.0 S SEQ Comments: SECOND OF SEVEN EXPOSURES TO BE MADE IN ONE ORBIT; REPEAT 8 TIMES TO GET COMPLETE LONGITUDE COVERAGE OF ROTATING ASTEROID ------------------------------------------------------------------------------------------------------------------------------------ 3 DEFINE VESTA WFPC2 IMAGE PC1 F1042M 10201 1 10.0 S 100 1 1 CYCLE 4 VESTA- 10.0 S SEQ Comments: THIRD OF SEVEN EXPOSURES TO BE MADE IN ONE ORBIT; REPEAT 8 TIMES TO GET COMPLETE LONGITUDE COVERAGE OF ROTATING ASTEROID ------------------------------------------------------------------------------------------------------------------------------------ 4 DEFINE VESTA WFPC2 IMAGE PC1 F673N 6732 1 2.0 S 100 1 1 CYCLE 4 VESTA- 2.0 S SEQ Comments: FOURTH OF SEVEN EXPOSURES TO BE MADE IN ONE ORBIT; REPEAT 8 TIMES TO GET COMPLETE LONGITUDE COVERAGE OF ROTATING ASTEROID ------------------------------------------------------------------------------------------------------------------------------------ 5 DEFINE VESTA WFPC2 IMAGE PC1 F953N 9534 1 20.0 S 100 1 1 CYCLE 4 VESTA- 20.0 S SEQ Comments: FIFTH OF SEVEN EXPOSURES TO BE MADE IN ONE ORBIT; REPEAT 8 TIMES TO GET COMPLETE LONGITUDE COVERAGE OF ROTATING ASTEROID ------------------------------------------------------------------------------------------------------------------------------------ 6 DEFINE VESTA WFPC2 IMAGE PC1 F439W 4300 1 1.0 S 100 1 1 CYCLE 4 VESTA- 1.0 S SEQ Comments: SIXTH OF SEVEN EXPOSURES TO BE MADE IN ONE ORBIT; REPEAT 8 TIMES TO GET COMPLETE LONGITUDE COVERAGE OF ROTATING ASTEROID ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5489 [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 7 DEFINE VESTA WFPC2 IMAGE PC1 F673N 6732 1 2.0 S 100 1 1 CYCLE 4 VESTA- 2.0 S SEQ Comments: SEVENTH OF SEVEN EXPOSURES TO BE MADE IN ONE ORBIT; REPEAT 8 TIMES TO GET COMPLETE LONGITUDE COVERAGE OF ROTATING ASTEROID ------------------------------------------------------------------------------------------------------------------------------------ 101 USE PHASE 0.00 +/- VESTA- 0.04 OF REF 1.0 SEQ GROUP 101-108 WITHIN 14D Comments: SINGLE-CCD (PC1) READOUT OK. ------------------------------------------------------------------------------------------------------------------------------------ 102 USE PHASE 0.125 +/- VESTA- 0.04 OF REF 1.0 SEQ Comments: SINGLE-CCD (PC1) READOUT OK. ------------------------------------------------------------------------------------------------------------------------------------ 103 USE PHASE 0.250 +/- VESTA- 0.04 OF REF 1.0 SEQ Comments: SINGLE-CCD (PC1) READOUT OK. ------------------------------------------------------------------------------------------------------------------------------------ 104 USE PHASE 0.375 +/- VESTA- 0.04 OF REF 1.0 SEQ Comments: SINGLE-CCD (PC1) READOUT OK. ------------------------------------------------------------------------------------------------------------------------------------ 105 USE PHASE 0.500 +/- VESTA- 0.04 OF REF 1.0 SEQ Comments: SINGLE-CCD (PC1) READOUT OK. ------------------------------------------------------------------------------------------------------------------------------------ 106 USE PHASE 0.625 +/- VESTA- 0.04 OF REF 1.0 SEQ Comments: SINGLE-CCD (PC1) READOUT OK. ------------------------------------------------------------------------------------------------------------------------------------ 107 USE PHASE 0.750 +/- VESTA- 0.04 OF REF 1.0 SEQ Comments: SINGLE-CCD (PC1) READOUT OK. ------------------------------------------------------------------------------------------------------------------------------------ 108 USE PHASE 0.875 +/- VESTA- 0.04 OF REF 1.0 SEQ Comments: SINGLE-CCD (PC1) READOUT OK. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5489 [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category MINOR PLANETS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4; SEQ 1-7 NON-INT; PCS MODE F / 1-7; PERIOD 5.34213H +/- 0.00001H; ZERO-PHASE 25-DEC-1994 +/- 0D PHASE 0.00 +/- 0.04 OF REF 1.0; GROUP 101-108 WITHIN 14D PHASE 0.125 +/- 0.04 OF REF 1.0 PHASE 0.250 +/- 0.04 OF REF 1.0 PHASE 0.375 +/- 0.04 OF REF 1.0 PHASE 0.500 +/- 0.04 OF REF 1.0 PHASE 0.625 +/- 0.04 OF REF 1.0 PHASE 0.750 +/- 0.04 OF REF 1.0 PHASE 0.875 +/- 0.04 OF REF 1.0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F673N F953N F1042M F439W ------------------------------------------------------------------------------------------------------------------------------------ Target Names VESTA ------------------------------------------------------------------------------------------------------------------------------------