Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5508 Report Date: 18-Jul-95:17:33 Version: ********** Check-in Date: ********** 1.Proposal Title: TRACKING FEATURES IN TITAN'S LOWER ATMOSPHERE AND ON ITS SURFACE: CYCLE4 HIGH ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID SOLAR SYSTEM GO Sub Category SATELLITES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Peter H Smith LUNAR AND PLANETARY LABORATO USA (602) 621-2725 ------------------------------------------------------------------------------------ 7. Abstract We propose here to take a major step forward in the study of Titan's atmosphere and surface by doing a partial survey of the detectable features at red and NIR wavelengths, probing from 100km to the surface. In cycle 2 of the HST, 8 images of Titan were obtained with the Planetary Camera; in the F850LP, several small- scale features, that could be either on the surface or in the lower atmosphere, or both, were clearly seen (Smith et al., 1992). The 1992 images proved the ex- istence of trackable features; however, the photometry is inaccurate because of the image reconstruction difficulties with WFPC1. A partial orbital revolution of Titan will now be observed, with several filter sets, at several intervals. We will identify, track, and characterize all surface and near-surface features using five filters chosen to sound the altitude range. Methane band filters are particularly useful in providing high contrast and accurate altimetry. Features tidally locked with Saturn are likely to be on the surface. Features not synch- ronous with Saturn are probably atmospheric. Wind vectors can be derived from them. A three-dimensional map of observed features, and their velocity vectors, will be produced, using time history and limb-darkening information. The final product will include a new global circulation model for Titan, a revised atmos- pheric scattering model and a surface map. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 7.00 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5508 PI: Peter H Smith Proposal Title: TRACKING FEATURES IN TITAN'S LOWER ATMOSPHERE AND ON ITS SURFACE: CYCLE4 HIGH ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Peter H Smith LUNAR AND PLANETARY LABORATORY USA John J Caldwell INSTITUTE FOR SPACE AND CANADA TERRESTRIAL SCIENCE Michael D Allison NASA GODDARD INSTITUTE FOR SPACE USA SCIENCE Lawrence A Sromovsky UNIVERSITY OF WISCONSIN-MADISON USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. The first executable lines in the exposure logsheet, 71.00 to 80.00 inclusive, constitute a spectral survey of Titan's contrast features from 336 nm to 1042 nm. The primary purpose of this survey is to compare the current state of the atmosphere of Titan with earlier epochs, including both previous HST imaging and Voyage observations from a dozen years ago. This survey is intended to be completed entirely within two consecutive HST visibility periods. Following this, different sequences (lines 11.00 to 13.00; 21.00 to 23.00; and 31.00 to 34.00) are repeated in exposure lines 81.00 to 92.00, at intervals specified in the REQ statements of each line. Each time a sequence is executed, it is required that it will be completed entirely within one HST visibility period. It may be acceptable to alter some of the AFTER REQs in lines 81 to 92. Please contact the P.I. if the nominal AFTER REQs cause difficulty in scheduling. The repeating sequences are intended to track atmospheric or surface features seen in earlier HST images. See question 5 below. In order to track cloud and surface features on Titan, it is highly desirable to record the feature 3 times as it moves across the disk on a single transit. Our goal is to measure 30-60% of all features moving at +/- 50 m/s or less with respect to the surface. At +50 m/s, a feature moves 40 deg in longitude in 7.4 hr. Therefore, we propose to space the first 7 observations by this amount, with leeway up to 1.5 hr to facilitate scheduling HST. The survey filters (see section 1 above) give the global context of the atmosphere from the surface to upper level haze. This is executed on two consecutive HST visibility periods, to begin the program. The next 6 exposure lines, defined by SEQUENCE 1, regularly spaced by 7.4 hr, include only the 850, 673 and 619 nm filters, have the greatest chance for seeing down to 20-50 km above the surface, where the fastest detectable winds are expected. These are followed alternately by SEQUENCE 2 and SEQUENCE 3, with intervals of 32 hr between observations. SEQUENCE 2 has the best chance to resolve low-altitude, slow moving features, because it includes the 1042 nm filter (while dropping the 673 nm filter to conserve time). SEQUENCE 3 also includes the 889 nm CH4 filter, which will track any apparent contrast features up to 750 km altitude. The scientific goals of this program do not allow breaking it into pieces. We are trying to learn about the evolution of cloud features by creating a time- lapse series showing temporal change as the features develop. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The HST is required for its high spatial resolution. It should also be noted that the spectral range of the WFPC2 filter set used here is significantly broader than the previous Voyager filter set, including high-contrast methane filters. Page 3 ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. The primary concern with scheduling is that the observations be obtained within +/- 1 month of opposition, if possible. A slight relaxation of this constraint would be considered. Furthermore, the spacings between various observations in this time series are calculated to optimize the scientific value of detections of atmospheric and/or surface features. It is not possible to anticipate all possible HST environmental constraints on the schedulability of our preferred time series, but we are prepared to discuss trade-offs if specific conflicts arise. See question 3 above. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. There are no special calibration requirements. We will require flat-fielding and standard absolute calibrations only. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. The RESOURCE estimation for this program is done for individual exposure lines and includes an accurate acounting for the real number of visits required by the HST. The correct number of GSACQs and GSREACQ (only one of the latter) are included in the overall RESOURCE total. ------------------------------------------------------------------------------------ 9. Description of previous HST work. Smith and Caldwell have both done previous HST Titan imaging programs. Caldwell is a GTO with other programs in planetary imaging and spectroscopy. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Computing facilites exist and have previously been used at both the University of Arizona and at the Institute for Space and Terretrial Science to reduce HST data. Both institutions have also participated in data analysis and reduction for numerous other NASA missions, including Galileo, Voyager, et al. There are no foreseeable technical issues involving scientific analysis capabilities. ------------------------------------------------------------------------------------ 11. Address Information Name: PETER H SMITH Category: PI Institution: LUNAR AND PLANETARY LABORATORY Address: UNIVERSITY OF ARIZONA City: TUCSON State: AZ Zip Code: 85721 Country: USA Telephone: 602-621-2725 Telex (or e-mail): PSMITH@LPL.ARIZONA.EDU FAX: 602-621-49 ------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 5508 [ 4] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: TITAN ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE TITAN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD = SATURN | STD = TITAN | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |V=8.36 | 2 |B-V=1.30 | 3 |U-B=0.75 | | ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5508 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 DEFINE TITAN WFPC2 IMAGE PC1 F673N ATD-GAIN=15 1 40S 10 1 1 SEQUENC 2 E1 3 ------------------------------------------------------------------------------------------------------------------------------------ 12 DEFINE TITAN WFPC2 IMAGE PC1 F850LP ATD-GAIN=15 1 22S 10 1 1 SEQUENC 2 E1 3 ------------------------------------------------------------------------------------------------------------------------------------ 13 DEFINE TITAN WFPC2 IMAGE FQCH4N1 FQCH4N15 6193 ATD-GAIN=15 1 80S 10 1 1 SEQUENC 5 2 E1 3 ------------------------------------------------------------------------------------------------------------------------------------ 21 DEFINE TITAN WFPC2 IMAGE PC1 F850LP ATD-GAIN=15 1 22S 10 1 1 SEQUENC 2 E2 3 ------------------------------------------------------------------------------------------------------------------------------------ 22 DEFINE TITAN WFPC2 IMAGE PC1 F1042M ATD-GAIN=7 1 200S 10 1 1 SEQUENC 2 E2 3 ------------------------------------------------------------------------------------------------------------------------------------ 23 DEFINE TITAN WFPC2 IMAGE FQCH4N1 FQCH4N15 6193 ATD-GAIN=15 1 80S 10 1 1 SEQUENC 5 2 E2 3 ------------------------------------------------------------------------------------------------------------------------------------ 31 DEFINE TITAN WFPC2 IMAGE PC1 F850LP ATD-GAIN=15 1 22S 10 1 1 SEQUENC 2 E3 3 ------------------------------------------------------------------------------------------------------------------------------------ 32 DEFINE TITAN WFPC2 IMAGE PC1 F1042M ATD-GAIN=7 1 200S 10 1 1 SEQUENC 2 E3 3 ------------------------------------------------------------------------------------------------------------------------------------ 33 DEFINE TITAN WFPC2 IMAGE FQCH4N1 FQCH4N15 6193 ATD-GAIN=15 1 80S 10 1 1 SEQUENC 5 2 E3 3 ------------------------------------------------------------------------------------------------------------------------------------ 34 DEFINE TITAN WFPC2 IMAGE FQCH4P1 FQCH4P15 8922 ATD-GAIN=7 1 100S 10 1 1 SEQUENC 5 2 E3 3 ------------------------------------------------------------------------------------------------------------------------------------ 71 TITAN WFPC2 IMAGE PC1 F336W ATD-GAIN=7 1 160S 10 1 1 CYCLE 4 2 GROUP 71-80 NO GAP 3 Comments: IT IS EXPECTED THAT GROUP 71-80 WILL BE COMPLETED ENTIRELY WITHIN TWO VISIBILITY PERIODS POSSIBLE, CONTACT P.I. ------------------------------------------------------------------------------------------------------------------------------------ 72 TITAN WFPC2 IMAGE PC1 F439W ATD-GAIN=15 1 40S 10 1 1 CYCLE 4 2 3 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5508 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 73 TITAN WFPC2 IMAGE PC1 F547M ATD-GAIN=15 1 7S 10 1 1 CYCLE 4 2 3 ------------------------------------------------------------------------------------------------------------------------------------ 74 TITAN WFPC2 IMAGE PC1 F588N ATD-GAIN=15 1 40S 10 1 1 CYCLE 4 2 3 ------------------------------------------------------------------------------------------------------------------------------------ 75 TITAN WFPC2 IMAGE PC1 F673N ATD-GAIN=15 1 40S 10 1 1 CYCLE 4 2 3 ------------------------------------------------------------------------------------------------------------------------------------ 76 TITAN WFPC2 IMAGE PC1 F791W ATD-GAIN=15 1 3S 10 1 1 CYCLE 4 2 3 ------------------------------------------------------------------------------------------------------------------------------------ 77 TITAN WFPC2 IMAGE PC1 F850LP ATD-GAIN=15 1 22S 10 1 1 CYCLE 4 2 3 ------------------------------------------------------------------------------------------------------------------------------------ 78 TITAN WFPC2 IMAGE FQCH4P1 FQCH4P15 8922 ATD-GAIN=7 1 100S 10 1 1 CYCLE 4 5 2 3 ------------------------------------------------------------------------------------------------------------------------------------ 79 TITAN WFPC2 IMAGE FQCH4N1 FQCH4N15 6193 ATD-GAIN=15 1 80S 10 1 1 CYCLE 4 5 2 3 ------------------------------------------------------------------------------------------------------------------------------------ 80 TITAN WFPC2 IMAGE PC1 F1042M ATD-GAIN=7 1 200S 10 1 1 CYCLE 4 2 3 ------------------------------------------------------------------------------------------------------------------------------------ 81 USE CYCLE 4 SEQUENC NON-INT E1 AFTER 71 BY 7.4H + /- 1H ------------------------------------------------------------------------------------------------------------------------------------ 82 USE CYCLE 4 SEQUENC NON-INT E1 AFTER 71 BY 14.9H +/- 1.5H ------------------------------------------------------------------------------------------------------------------------------------ 83 USE CYCLE 4 SEQUENC NON-INT E1 AFTER 71 BY 22.3H +/- 1.5H ------------------------------------------------------------------------------------------------------------------------------------ 84 USE CYCLE 4 SEQUENC NON-INT E1 AFTER 71 BY 29.8H +/- 1.5H ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5508 [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 85 USE CYCLE 4 SEQUENC NON-INT E1 AFTER 71 BY 37.2H +/- 1.5H ------------------------------------------------------------------------------------------------------------------------------------ 86 USE CYCLE 4 SEQUENC NON-INT E1 AFTER 71 BY 44.7H +/- 1.5H ------------------------------------------------------------------------------------------------------------------------------------ 87 USE CYCLE 4 SEQUENC NON-INT E3 AFTER 71 BY 80H +/ - 1.5H ------------------------------------------------------------------------------------------------------------------------------------ 88 USE CYCLE 4 SEQUENC NON-INT E2 AFTER 71 BY 112H + /- 1.5H ------------------------------------------------------------------------------------------------------------------------------------ 89 USE CYCLE 4 SEQUENC NON-INT E3 AFTER 71 BY 144H + /- 1.5H ------------------------------------------------------------------------------------------------------------------------------------ 90 USE CYCLE 4 SEQUENC NON-INT E2 AFTER 71 BY 176H + /- 1.5H ------------------------------------------------------------------------------------------------------------------------------------ 91 USE CYCLE 4 SEQUENC NON-INT E3 AFTER 71 BY 208H + /- 1.5H ------------------------------------------------------------------------------------------------------------------------------------ 92 USE CYCLE 4 SEQUENC NON-INT E2 AFTER 71 BY 272H + /- 1.5H ------------------------------------------------------------------------------------------------------------------------------------ 93 USE CYCLE 4 SEQUENC NON-INT E3 AFTER 71 BY 304H + /- 1.5H ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5508 [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ATD-GAIN ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 7.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category SATELLITES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4; GROUP 71-80 NO GAP; NON-INT; AFTER 71 BY 7.4H +/- 1H; AFTER 71 BY 14.9H +/- 1.5H; AFTER 71 BY 22.3H +/- 1.5H; AFTER 71 BY 29.8H +/- 1.5H; AFTER 71 BY 37.2H +/- 1.5H; AFTER 71 BY 44.7H +/- 1.5H; AFTER 71 BY 80H +/- 1.5H; AFTER 71 BY 112H +/- 1.5H; AFTER 71 BY 144H +/- 1.5H; AFTER 71 BY 176H +/- 1.5H; AFTER 71 BY 208H +/- 1.5H; AFTER 71 BY 272H +/- 1.5H; AFTER 71 BY 304H +/- 1.5H; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F673N F850LP FQCH4N15 F1042M FQCH4P15 F336W F439W F547M F588N F791W ------------------------------------------------------------------------------------------------------------------------------------ Target Names TITAN ------------------------------------------------------------------------------------------------------------------------------------