Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5020c Report Date: 09-May-96:20:17 Version: ********** Check-in Date: ********** 1.Proposal Title: SEPARATE LIGHTCURVES OF PLUTO AND CHARON-SPLIT OF 3848 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID SOLAR SYSTEM GO 1 Long Term yrs Sub Category MINOR PLANETS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. Marc W. Buie LOWELL OBSERVATORY USA 602-774-3358 ------------------------------------------------------------------------------------ 7. Abstract With this program we will begin a systematic effort to collect separate lightcurve data on the Pluto and Charon system. Such observations will continue to improve the albedo mapping of their surfaces by splitting the present ground-based ambiguity in the combined lightcurve. The 3848 obs. must be done at the such times when it is within 25 arcseconds of a star of similar brightness. Such data will provide both the lightcurves and the phase angle behavior of each object. In addition to the photometry, astrometric measurements of Pluto and Charon relative to each of the background field stars can be made from the imaging data. In sufficient quantity, these data will further refine our knowledge of the sizes and relative masses of Pluto and Charon. Continued work on the photometry will allow us to watch the lightcurve evolution as Pluto moves away from the sun and as the Sun progresses to higher and higher latitudes. 5020 is a continuation of 3848, replacing obs. lost in the safing event of Mar. 1993., and due to subsequent pointing restrictions. 5020 measures the Pluto-Charon system and the stars separately. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 12.14 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 5020c PI: Dr. Marc W. Buie Proposal Title: SEPARATE LIGHTCURVES OF PLUTO AND CHARON-SPLIT OF 3848 ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Marc W. Buie LOWELL OBSERVATORY USA David J. Tholen UNIVERSITY OF HAWAII USA Larry H. Wasserman LOWELL OBSERVATORY USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. All observations are blind-pointed PC exposures of the Pluto-Charon system while in the same PC6 field of view with a star similar in brightness to Pluto. For each appulse, we take two sets of exposures separated by at least 6 hours to get distinct lightcurve points. During 10 of the 12 appulses, we will take exposures only in F555W. During the other 2 appulses we will take exposures in F439W and F555W. The target pointing is constructed so that the telescope is pointed to and tracks the mid-point between the Pluto-Charon barycenter and the appulse star. The window on the target specification is defined to include only the time the star and Pluto can appear on PC6 for nominal roll. The window is conservative at a level of 3" on each side to allow for pointing errors from the guide stars and for slight off-nominal roll conditions. If off-nominal roll is required to schedule the observations, the PI can provide verification on whether the pointing will work or not. The only hard and fast rule for checking this is to see if Pluto and the star are on PC6 for the given time and roll angle. The PI is willing to provide additional information if off-nominal roll is required to schedule the observations. Tracking the mid-point between Pluto and the appulse star will cause some slight trailing for the F555W exposures and more noticeable trailing for the F439W exposures. Both Pluto and the star will be trailed by nearly equal amounts. To allow us to remove the effects of the trailing, we require full pointing (V1 and V3 on the plane-of-the-sky) reconstructions with each observation. We would also appreciate a FHST update immediately before each visit to provide the best possible information on roll angle. The default tracking mode of fine-lock is preferred for all observations but coarse-track is acceptable if there aren't enough stars to support fine-lock. We have chosen 12 appulses from the full set of 24. This set of 12 maximizes the scientific return for the allotted spacecraft time. However, some of these appulses may be unobservable due to SAA passages or lunar avoidance. The other 12 appulses are provided as backup observations if any of the original 12 cannot be scheduled. The PI must be contacted for the replacement observation since it depends on the coverage lost by the unschedulable observation. The primary set of observations from the SELECT SET are EXP LOG LINEs 10, 30, 50, 70, 90, 100, 130, 150, 170, 190, 210, and 220. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Separating the individual lightcurves of Pluto and Charon is a very difficult task from ground-based observatories. At best, their separation is 1 arc-sec. Under the best conditions from the best site at the best telescope (often considered to be CFHT on Mauna Kea), it is possible to get separate magnitudes for Pluto and Charon, near elongation, under conditions of excellent seeing. However, collecting a complete lightcurve becomes extremely difficult when conditions of telescope scheduling and weather are confronted. In this case, weather includes losing a night to bad seeing, not just poor photometric conditions. The telescope scheduling difficulties are not to be understated. Due to the slow rotation period of Pluto, photometric measurements are spread out over a large number of nights. These observations do not take very much time but at present scheduling practices at most telescopes preclude using a large number of partial nights. Also, resolved images near minimum separation cannot be obtained from the ground. The Hubble Space Telescope counters both of these difficulties. The enhanced spatial resolution of HST can easily separate the two bodies, even fairly close to minimum separation (about 0.2 arcsec). The image degradation caused by the spherical aberration may actually be beneficial to this project because more source photons can be collected per image. Given the low efficiency of this program, the photometric signal-to-noise ratio of the observations as a function of spacecraft time is greatly increased by the aberration. Also, the larger image size to pixel size ratio will permit a more accurate determination of the image centroid, thereby improving the relative astrometry of the two bodies. An additional advantage of HST is the way it is scheduled and run. An observation of this nature requiring periodic, short obseravations can be accomodated much more easily than with most ground-based observatories. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. This proposal will require special scheduling to ensure that Pluto is always seen in a field with another similarly bright star. All the special scheduling is provided as time windows on the target list. The initial set of observations chosen from the candiate SELECT set provides optimum lightcurve and solar phase angle coverage. ADDENDUM: This proposal (5020) replaces the portion of 3848 that could not be scheduled due to the SADE failure in Mar-Apr 1993. The strategy is changed to cover specific longitudes even when a field does not contain a field star. To make up for the loss in photometric accuracy with not having the field star, each Pluto observation is followed by a photometric reference star measurement. The conditional requirements are intended to ensure that a photometric reference is measured close in time to the Pluto observations. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. For accurate image deconvolutions and positional measurements we require full pointing reconstructions (RA and DEC vs. time) during each exposure. This will allow us to create numerical PSFs that match the actual jitter and tracking that occurs during each exposure. We also need the best possible knowledge of the roll angle of the spacecraft. If possible, please schedule an FHST update immediately prior to each observation. Page 4 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. The data reduction and analysis will be carried out by the proposers on their currently available computers. We expect additional work to be carried out by a post-doc for whom we wish to procure a new workstation. The data reductions will require PSF fitting to establish the magnitudes and relative positions of Pluto, Charon, and the field star. These data must be cross referenced with the nearly simultaneous ground-based observations of the combined magnitudes to complete the photometric reductions prior to modeling. Ground-based astrometry must also be collected so that the astrometric net provided by the appulse star can be calibrated. We plan to try conventional Schmidt astrometry on this field but if this proved inadequate we will do the astrometry using wide-field plates to be taken at CFHT on Mauna Kea. Our goal is to obtain astrometry at the 0.001" level. This may prove infeasible but is required to advance our knowledge of the individual densities of Pluto and Charon. Once the astrometric and lightcurve reductions are complete, the observations will be added to existing orbit and albedo models. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. Ground-based observations will be required to establish a high-precision astrometric net which will tie together all the individual HST observations. This net of stars will cover all of the appulse stars in our candiate list. Without these supporting observations, we will be unable to provide any information about the barycentric motion of Pluto and Charon. We also must continue to provide ground-based combined lightcurve measurements. The photometric accuracy of HST and the PC are insufficient for our models. By combining extremely accurate low spatial resolution ground-based observations with lower accuracy high spatial resolution data, we can achieve significant improvements in our model of the surface of Pluto and Charon. The ground-based observations are essential for maximizing the return from the HST data. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). The PI and Co-I's already have most of the computer facilities and the necessary access to ground-based telescopes to support this project. The PI will also work to secure computing time from supercomputer centers such as NCSA or SDSC to support the albedo modeling efforts. ------------------------------------------------------------------------------------ 11. Address Information Name: MARC W. BUIE Category: PI Institution: LOWELL OBSERVATORY Address: MARS HILL ROAD, 1400 WEST City: FLAGSTAFF State: AZ Zip Code: 86001 Country: USA Telephone: (602)774-3358 Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5020c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 107 GSC-5011- A 125; RA = 15H 29M 00.089S +/- J2000 1 V=14.96+/-0.5 0069 0.001S, DEC = -04D 07' 46.51" +/- 0.01" Comments: PHOTOMETRIC REFERENCE STAR. ------------------------------------------------------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 5020c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: PL-CH-A ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET PLUTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=PLUTO | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | CML OF PLUTO FROM EARTH BETWEEN 347 353 | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |V=14.164+/-0.042 | 2 |B-V=0.842+/-0.001 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: PL-CH-B ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET PLUTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=PLUTO | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | CML OF PLUTO FROM EARTH BETWEEN 212 218 | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |V=14.164+/-0.042 | 2 |B-V=0.842+/-0.001 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 5020c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 3 | TARGET NAME: PL-CH-C ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET PLUTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=PLUTO | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | CML OF PLUTO FROM EARTH BETWEEN 187 193 | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |V=14.164+/-0.042 | 2 |B-V=0.842+/-0.001 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 4 | TARGET NAME: PL-CH-D ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET PLUTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=PLUTO | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | CML OF PLUTO FROM EARTH BETWEEN 119 125 | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |V=14.164+/-0.042 | 2 |B-V=0.842+/-0.001 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET LIST b)Solar System Targets ID = 5020c [ 8] ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 5 | TARGET NAME: PL-CH-E ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET PLUTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=PLUTO | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | CML OF PLUTO FROM EARTH BETWEEN 37 43 | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |V=14.164+/-0.042 | 2 |B-V=0.842+/-0.001 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 6 | TARGET NAME: PL-CH-F ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET PLUTO ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=PLUTO | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | CML OF PLUTO FROM EARTH BETWEEN 7 13 | ------------------------------------------------------------------------------------------------------------------------------------ REF | DATA | COMMENTS | | 1 |V=14.164+/-0.042 | 2 |B-V=0.842+/-0.001 | | ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5020c [ 9] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 5 DEFINE # PC IMAGE PC6 F555W 2 30S 100 1 1 CYCLE 2 PLV ------------------------------------------------------------------------------------------------------------------------------------ 10 USE PLV PL-CH-A Comments: GROUP 10-61 WITHIN 6.4D; ------------------------------------------------------------------------------------------------------------------------------------ 11 USE PLV GSC-5011- 0069 ------------------------------------------------------------------------------------------------------------------------------------ 20 USE PLV PL-CH-B ------------------------------------------------------------------------------------------------------------------------------------ 21 USE PLV GSC-5011- COND IF 11,20 GT 6 0069 DAYS APART ------------------------------------------------------------------------------------------------------------------------------------ 30 USE PLV PL-CH-C ------------------------------------------------------------------------------------------------------------------------------------ 31 USE PLV GSC-5011- COND IF 11,30 GT 6 0069 DAYS APART ------------------------------------------------------------------------------------------------------------------------------------ 40 USE PLV PL-CH-D ------------------------------------------------------------------------------------------------------------------------------------ 41 USE PLV GSC-5011- COND IF 11,40 GT 6 0069 DAYS APART ------------------------------------------------------------------------------------------------------------------------------------ 50 USE PLV PL-CH-E ------------------------------------------------------------------------------------------------------------------------------------ 51 USE PLV GSC-5011- COND IF 11,50 GT 6 0069 DAYS APART ------------------------------------------------------------------------------------------------------------------------------------ 60 USE PLV PL-CH-F ------------------------------------------------------------------------------------------------------------------------------------ 61 USE PLV GSC-5011- COND IF 11,60 GT 6 0069 DAYS APART ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5020c [ 10] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations PC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 12.14 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category MINOR PLANETS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 2; COND IF 11,20 GT 6 DAYS APART COND IF 11,30 GT 6 DAYS APART COND IF 11,40 GT 6 DAYS APART COND IF 11,50 GT 6 DAYS APART COND IF 11,60 GT 6 DAYS APART ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GSC-5011-0069 PL-CH-A PL-CH-B PL-CH-C PL-CH-D PL-CH-E PL-CH-F ------------------------------------------------------------------------------------------------------------------------------------