Phase 1 submission for Active Asteroid P/2013 R3-657840800Assigned ID: 150
----- Attempting Submission 1 (Thu Apr 10 02:07:19 GMT 2014) -----Updated the orbital elements to JPL #2.-80823542----- Attempting Submission 1 (Wed Jul 23 00:38:04 GMT 2014) -----
----- Attempting Submission 2 (Wed Jul 23 19:37:25 GMT 2014) -----
----- Attempting Submission 3 (Thu Aug 21 13:32:35 GMT 2014) -----
----- Attempting Submission 4 (Tue Sep 16 03:16:46 GMT 2014) -----APT 22.2.1 won't run properly on my Mac. Specifically, the Orbit Planner doesn't run
for some subtle reason. I've been working on this with Karla Peterson for many months,
but no solution is in sight.Determining the Nature and Origin of Mass Loss from Active Asteroid P/2013 R3We propose a program of WFC3 images of the active asteroid P/2013 R3 in order to determine the nature and origin of mass loss from this object. R3 has a unique, multiple nucleus structure in which the components are measured to separate at sub-meter per second velocities. It is best explained as a rotational breakup (presumably resulting from the YORP torque). We will obtain images over a wide time base in Cycle 22 in order to determine the orbits of the fragments and we will obtain time-series, high resolution photometry in order to measure their rotations. Rotational breakup and rotational mass-shedding are suspected to be the main mechanisms of destruction for sub-kilometer asteroids. Neither has been observed before but, between P/2013 R3 and P/2013 P5 (subject of another proposal) we have the first, potentially ground-breaking opportunities to observe both.We request a total of 10 orbits devoted to the temporal evolution of P/2013 R3. Seven single-orbit "evolution" visits to P/2013 R3 are requested between 2014 Oct 01 and 2015 May 30, when the object enters the Sun exclusion zone (elongation 50 deg). Single-orbit visits using the WFC3 F350LP filter provide sufficient sensitivity to image faint structures and enough images for adequate cosmic ray and artifact rejection, as established by our ToO work. A ~30 to 40 day timescale between visits is suggested by the changing observational geometry (Figure 3) and by the likely dynamical evolution of the object. In 30 days, the expected motion between fragments is 1 arcsec (25 pixels). Much faster sampling would be unjustified while slower sampling would risk confusion between changes caused by geometry and changes intrinsic to the object. Separate from the dynamical timescale, each fragment likely has a (not constrained) physical timescale associated with the depletion of dust by radiation pressure. Visits separated by longer than a month risk losing fragments to physical decay. Taking the measured velocity dispersion of the fragments from Jewitt et al. (2014), namely 0.2 to 0.5 m/s, we predict a spread of 0.6x107 to 1.5x107 m between 2013 Oct and 2014 Oct. At typical geocentric distance 3 AU (Figure 3), this corresponds to 3 to 7 arcseconds motion in the sky plane. Even with a modest acceleration due to Keplerian shear or rocket forces, the entire ensemble of fragments should remain well within the 160 arcsec wide field of WFC3. The science objectives cannot be met using other facilities. The HST is vastly superior to Keck for the program proposed here (compare Figures 1 and 2). We especially need Hubble's high angular resolution and stable point-spread function (PSF) to examine small structures within the diffuse coma and to study the close environs of the nucleus, to constrain the dynamics and mechanisms responsible for the unusual behavior of this active asteroid. There is no adaptive- optics solution for this faint target (the brightest discrete source has V=26) and, in any case, the AO PSF is too unstable for coma fitting using Lamy's established technique (e.g., Lamy et al. 2009). During Cycle 22 (as in Cycle 21), the R3 fragments will be extremely faint (see Fig. 4) and will be pushing the sensitivity limits of HST. Nevertheless, our previous observations and the WFC3 ETC demonstrate that our program is feasible. For each of the HST orbits, we expect to obtain 6 deep exposures (5 x 348s + 1 x 233s) using the F350LP filter. ETC ID 583446 (using 5 x 348s only) gives S/N=3.1 and 12.9 (optimal extraction) in a 0.4 arcsec aperture for V=27.5, which shows we can meet our measurement objectives for the R3 fragments. Figure 4 shows the apparent V-band magnitude of a 200 m radius sphere having albedo 0.05 and moving in the orbit of R3. There is a roughly 1 magnitude variation through Cycle 22, with peak brightness expected on UT 2015 Jan 18, and observations before this time being slightly favored over observations after it. R3 is outside the (50 degree) HST solar exclusion zone from UT 2014 Oct 01 to May 30. Scheduling for the dynamics observations is constrained by the need to obtain sufficient visits to connect fragments observed at different times. This was already difficult in our Cycle 21 data with a sampling of ~4 weeks, owing to photometric and morphological evolution on similar timescales. A possible set of observing dates is: 2014 Oct 3, Nov 3, Dec 10, 2015 Jan 18, Mar 04, Apr 10, May 28 (7 orbits). The observations all have flexible observing windows (e.g. 1 week) except that 1) we request the first visit to occur as soon as possible in order to establish the starting morphology in Cycle 22 and to allow a connection to be made to the Cycle 21 data (which ended 2014 Feb) and 2) we request a visit on 2015 Mar 04 to coincide with Earth's passage through the R3 orbital plane. The latter configuration removes all ambiguity about projection effects on material above and below the plane. Scheduling for the rotational/size/shape science is best done near UT 2015 Jan 18, the date of peak brightness (Figure 4). Four consecutive orbits will provide a ~4 hour baseline of coverage over which any true rotational variation should repeat. Observations over a shorter time would be correspondingly more difficult to associate unambiguously with the rotation of the fragments (as opposed to brightness fluctuations from other causes). The 4 orbits near Jan 18 could of course stand-in for one of the dynamics observations. The total request is therefore for 7 + 4 - 1 = 10 orbits with WFC3.SOLAR SYSTEMDefaultfalsefalsefalsefalsefalseSUPPORTEDSOLAR SYSTEMJPL #1 solution for R3-AASTEROIDMBC-P2013R3TYPE=COMET,Q=2.20377481462572,E=0.2733288372094057,I=0.8979872165430337,O=342.6413289368975,W=8.324789778007844,T=05-AUG-2013:06:45:16,TTimeScale=UTC,EQUINOX=J2000,EPOCH=18-DEC-2013:00:00:00,EpochTimeScale=UTCEARTHWFC3/UVISImagingNoNoF350LPWFC3/UVISImagingNoNoF350LPWFC3/UVISImagingNoNoF350LPWFC3/UVISImagingNoNoF350LPWFC3/UVISImagingNoNoF350LPWFC3/UVISImagingNoNoF350LPWFC3/UVISImagingNoNoF350LP52.5Using ephemeris for target 13865-10-P2013R3-Aephemeris data for target 13865-10-P2013R3-A does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 14.213 to 16.090. ephemeris interval: 14.243 to 16.245The scheduling data was generated by CASM 22.2.CASM was run in Phase II mode.(Tic-Visit
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