12597( 4) - 21-Nov-2011 14:07:53 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12597 Version: 4 Check-in Time: 21-Nov-2011 14:07:53 STScI Edit Number: 0 Title Hubble Imaging of a Newly Discovered Main Belt Comet ------------------------------------------------------------------------------------ Type Cycle GO 19 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. David Jewitt University of California - Los Angeles CoI: Dr. Harold A. Weaver The Johns Hopkins University Applied Y Physics Laboratory CoI: Mr. Max Mutchler Space Telescope Science Institute N CoI: Dr. Stephen M. Larson University of Arizona N CoI: Dr. Michal Drahus University of California - Los Angeles N CoI: Dr. Jessica Agarwal Universitat Potsdam N ------------------------------------------------------------------------------------ Abstract We seek two orbits of Target of Opportunity (ToO) time to secure exploratory observations of a main-belt comet (MBC), should one be discovered in the upcoming proposal cycle. The observations will be used to determine the early-time morphology and to assess its rate of change by comparison of data from two epochs. The ToO data are needed to determine the optimum strategy for subsequent observations, intended to characterize the MBC at the highest resolution and so to determine the driver of the cometary activity. Our previous Hubble observations of MBCs P/2010 A2 and (596) Scheila were obtained in emergency mode through Director's Discretionary Time requests. The Director's office has suggested that we propose to follow up future MBC discoveries as a ToO, so that HST observations could begin sooner. ------------------------------------------------------------------------------------ Observations Description ------------------------ Our observing strategy will be dictated by the specific target discovered. For an MBC having a relatively faint nucleus (e.g., P/2010 A2), we expect to take 5 or 6 images with long exposure times (400-500 s) in a broadband filter (F606W) to provide a deep search for debris. But if the MBC has a relatively bright nucleus, we will take both short and long exposures, and possibly use a narrow band filter for the short exposures. For example, for asteroid (596) Scheila with its ultra-bright nucleus (V=13.7), we used an exposure time of 0.5 sec (the shortest available) and the F621M filter to avoid saturation while still obtaining S/N=200 on the nucleus itself in search of structure at 100 km scales. In all cases, we will obtain approximately half the images at one location on the CCD and then 12597( 4) - 21-Nov-2011 14:07:53 - [ 2] repeat that sequence of images at a dithered location. Dithered, multiple images provide protection from bad pixels and cosmic ray strikes that otherwise might compromise the photometry. Previous HST observations show that the timescale for substantial change is from several weeks (Scheila) to several months (P/2010 A2). Therefore, while the first observation should be scheduled as soon as possible after the target is discovered, the science does not require that the first visit be secured within the first two weeks. The first visit will set the scene, by establishing the high-resolution morphology of the object (at ~60 km/pixel at 2 AU geocentric distance). The second visit, ideally separated from the first by ~10 days, will reveal the changes. The two visits together will allow us to make a rational decision about the need for further observations with HST. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- This is a Target of Opportunity program that will be activated upon the discovery of a new Main Belt Comet. Please note that the orbital elements must be updated with those of the newly discovered object *before* doing any detailed planning of the observations. ------------------------------------------------------------------------------------ 12597( 4) - 21-Nov-2011 14:07:53 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: MBC-300163 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: COMET Main Belt Comet ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=COMET, Q=2.4378652, E=0.2011255, I=3.23918, O=83.20655, W=281.88617, T=18-JUL-2011:13:00:05, TTimeScale=TDB, EQUINOX=J2000, EPOCH=27-AUG-2011:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 20 +/- 2 Main belt asteroid 300163 (2006 VW139) has recently been identified as a Main Belt Comet (MBC). Ephemeris Center: EARTH Ephemeris Uncertainty: 14500 KM Acquisition Uncertainty: 10 " ------------------------------------------------------------------------------------------------------------------------------------ 12597( 4) - 21-Nov-2011 14:07:53 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 350 S REQ EPHEM CORR MBCV01 S ------------------------------------------------------------------------------------------------------------------------------------ 2 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 350 S REQ EPHEM CORR MBCV01 S ------------------------------------------------------------------------------------------------------------------------------------ 3 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 350 S REQ EPHEM CORR MBCV01 S ------------------------------------------------------------------------------------------------------------------------------------ 4 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 350 S POS TARG 0.2, 2.41; REQ S EPHEM CORR MBCV01 ------------------------------------------------------------------------------------------------------------------------------------ 5 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 350 S POS TARG 0.2, 2.41; REQ S EPHEM CORR MBCV01 ------------------------------------------------------------------------------------------------------------------------------------ 6 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 250 S POS TARG 0.2, 2.41; REQ S EPHEM CORR MBCV01 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ MBC-300163 1 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S MBC-300163 2 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S MBC-300163 3 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S MBC-300163 4 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S MBC-300163 5 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S MBC-300163 6 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S 12597( 4) - 21-Nov-2011 14:07:53 - [ 5] Visit: 02 Visit Requirements: AFTER 01 BY 8 D TO 12 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 350 S REQ EPHEM CORR MBCV02 S ------------------------------------------------------------------------------------------------------------------------------------ 2 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 350 S REQ EPHEM CORR MBCV02 S ------------------------------------------------------------------------------------------------------------------------------------ 3 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 350 S REQ EPHEM CORR MBCV02 S ------------------------------------------------------------------------------------------------------------------------------------ 4 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 350 S POS TARG 0.2, 2.41; REQ S EPHEM CORR MBCV02 ------------------------------------------------------------------------------------------------------------------------------------ 5 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 350 S POS TARG 0.2, 2.41; REQ S EPHEM CORR MBCV02 ------------------------------------------------------------------------------------------------------------------------------------ 6 MBC-300163 WFC3/UVI ACCUM UVIS1 F606W CR-SPLIT=NO 1 250 S POS TARG 0.2, 2.41; REQ S EPHEM CORR MBCV02 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ MBC-300163 1 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S MBC-300163 2 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S MBC-300163 3 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S MBC-300163 4 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S MBC-300163 5 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S MBC-300163 6 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S 12597( 4) - 21-Nov-2011 14:07:53 - [ 6] Summary Form for Proposal 12597 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 8 D TO 12 D, POS TARG 0.2, 2.41, REQ EPHEM CORR MBCV01, REQ EPHEM CORR MBCV02 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names MBC-300163 ------------------------------------------------------------------------------------------------------------------------------------