Determining the Nature and Origin of Mass Loss from Active Asteroid P/2013 P5

Phase 1 for Active Asteroid P/2013 P5. 1996283038 Assigned ID: 156 ----- Attempting Submission 1 (Thu Apr 10 02:36:57 GMT 2014) ----- Orbit number missing (probably due to addition of this sub-exposure after previous Orbit Planner processing). To learn more about orbit numbers, please read the full error text in the Diagnostic Report. Orbit number missing (probably due to addition of this sub-exposure after previous Orbit Planner processing). To learn more about orbit numbers, please read the full error text in the Diagnostic Report. Orbit number missing (probably due to addition of this sub-exposure after previous Orbit Planner processing). To learn more about orbit numbers, please read the full error text in the Diagnostic Report. Orbit number missing (probably due to addition of this sub-exposure after previous Orbit Planner processing). To learn more about orbit numbers, please read the full error text in the Diagnostic Report. Updated orbital elements to JPL#19, used in visits 40-70 -580026449 ----- Attempting Submission 1 (Wed Jul 23 00:39:10 GMT 2014) ----- ----- Attempting Submission 2 (Mon Oct 06 12:52:11 GMT 2014) ----- ----- Attempting Submission 3 (Mon Oct 06 13:33:42 GMT 2014) ----- ----- Attempting Submission 4 (Mon Oct 27 14:04:05 GMT 2014) ----- ----- Attempting Submission 5 (Fri Feb 27 18:43:53 GMT 2015) ----- HST Phase II Proposal 13866 (13866.apt) successfully submitted. Receipt: # 13866-5 ----- Attempting Submission 6 (Fri Feb 27 19:09:58 GMT 2015) ----- ----- Attempting Submission 7 (Fri Feb 27 21:00:46 GMT 2015) ----- ----- Attempting Submission 8 (Mon Mar 02 17:54:07 GMT 2015) ----- I got an error when trying to run the orbit planner, apparently because of a continuing communication problem between my computer and the STScI. I will report this to Karla Peterson. Determining the Nature and Origin of Mass Loss from Active Asteroid P/2013 P5 We propose a program of WFC3 images of active asteroid P/2013 P5 in order to determine the nature and origin of mass loss from this object. P5 ejects dust episodically, creating a multi-tailed appearance unlike that of any other known asteroid or comet. The ejection is thought to result from surface rotational instabilities (a process called "mass-shedding" by modelers). We will test the role of rotation by measuring the lightcurve of the nucleus and we will study the evolution of continued mass loss through Cycle 22. 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 P5 and P/2013 R3 (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 this MBC. P/2013 P5 lies outside the HSTs 50 degree Sun exclusion zone from 2014 Oct 15 and 2015 Aug 26. It reaches opposition on 2015 Mar 19, while the Earth crosses its orbit plane on 2014 Dec 31 and 2015 Jul 01. The variation of apparent magnitude in Cycle 22 (scaled from Cycle 21 data) is shown in Figure 4. Single-orbit visits using the WFC3 F350LP filter provide us with sufficient sensitivity to image faint structures and enough images for adequate cosmic ray and artifact rejection, as established by our ToO work. We possess only a limit to the size (and brightness) of the nucleus of P5 derived from dust- contaminated Cycle 21 WFC3 observations. Accepting the brightest possible nucleus, and the complete absence of background dust, the WFC3 ETC gives integrations from 54 to 513 s for photometry at SNR 100 in a standard 0.4 arcsec aperture, using the F350LP filter. Longer integrations will be needed if the nucleus is substantially fainter, or if there is non-zero coma contamination. Regardless, WFC3 offers sufficient sensitivity to study the lightcurve of P5 with good time resolution. We will combine the images from each visit to increase sensitivity to extend tails. The science objectives cannot be met using other facilities. We need Hubbles high angular resolution and stable point-spread function (PSF) to photometrically isolate the nucleus from surrounding dust. For example, we routinely employ a 0.2 arcsec radius aperture on HST whereas on Keck we are forced by seeing to use apertures 5 to 10 times larger to obtain photometric stability. These larger apertures capture a larger proportion of light scattered from near-nucleus dust, corrupting the photometry. Adaptive-optics observations are wholly unsuitable, owing to the PSF (and resulting photometric) instabilities that are an inevitable feature of this technique. P5 is also far too faint to be observed using self-tracking AO techniques and its motion relative to wavefront reference stars is additionally problematic. There is a roughly 2 magnitude variation through Cycle 22 (Figure 4), with peak brightness expected on UT 2015 Mar 19. Figure 5 shows synchrone predictions for the dust tail position angles. It reveals that before Mar 11 projection effects cause all synchrones to project to approximately the same p.a. Dust observations are preferred after Mar 11, when the tail p.a. swings wildly with time, providing maximum diagnostics from the data. We request 1 orbit in 2014 Nov to assess the morphology and dust quantity, then visits on 4 occasions in the Mar 11 - Jun 10 period when the tail p.a. is most sensitive to the ejection epoch. For nucleus rotation determination we request 4 consecutive orbits near opposition (2015 Mar 19), so as to maximize the brightness. Four consecutive orbits will provide a 4 hour baseline of coverage enough to show two periods of the expected 2 hr rotation. Observations over two periods are the minimum needed to be sure that rotation is responsible, as opposed to activity- related, non-periodic brightness fluctuations. A possible set of observing dates is Tail dynamics orbits: 2014 Nov 10, 2015 Mar 11, Apr 10, May 08, Jul 01, Aug 01 (6 x 1 orbits) Nucleus rotation: Mar 19 (4 orbits), for a total of 6 + 4 = 10 orbits with WFC3. 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 2) we request a visit on 2015 Jul 01 to coincide with Earths passage through the P5 orbital plane. The latter configuration removes all ambiguity about projection effects on material above and below the plane. From our synchrone interpretation, we predict negligible vertical extent of the dust because radiation pressure has no out-of -plane component. The measured thickness will give us the ejection speed, an important parameter for disruption models. SOLAR SYSTEM 12 Regular false false false false false SUPPORTED SOLAR SYSTEM JPL #17 orbital elements COMET Comet 2013 P5 TYPE=COMET,Q=1.936389452609925,E=0.1152839802288967 ,I=4.968466064328145,O=279.2894732263348,W=144.209729874557,T=15-APR-2014:18:07:56,TTimeScale=TDB,EQUINOX=J2000,EPOCH=14-JUN-2013,EpochTimeScale=TDB EARTH SOLAR SYSTEM JPL #19 orbital elements COMET Comet 2013 P5 TYPE=COMET,Q=1.936378759609211,E=0.1152834645135037 ,I=4.968458674964833,O=279.2894280674857,W=144.2127841838233,T=15-APR-2014:18:19:05,TTimeScale=TDB,EQUINOX=J2000,EPOCH=23-JUN-2013,EpochTimeScale=TDB EARTH WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP 1405906151238 52.5 The scheduling data was generated by CASM 22.2. 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