0Assigned ID: 535
----- Attempting Submission 1 (Fri Aug 24 18:25:12 GMT 2018) -----FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser
FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser
FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browserCreated a new target for visit 3 with the "EPHEM_UNCERT" keywort and added "requires ephemeris correction" to visit 3. The orbit solution is unchanged.-284550063----- Attempting Submission 8 (Fri Sep 21 15:13:11 GMT 2018) -----
----- Attempting Submission 9 (Tue Sep 25 13:33:44 GMT 2018) -----
----- Attempting Submission 10 (Wed Oct 03 09:10:12 GMT 2018) -----
HST Phase II Proposal 15623 (p3_ddt_phase2_eph_uncert_V2_181003.apt) successfully submitted.
Receipt: # 15623-10
----- Attempting Submission 11 (Wed Oct 03 09:39:57 GMT 2018) -----
----- Attempting Submission 12 (Mon Oct 29 19:22:04 GMT 2018) -----
----- Attempting Submission 13 (Thu Nov 29 15:24:22 GMT 2018) -----The FLASH level warnings disappear if the ETC is run with the zodiacal light calculated for the specific sky position and date. The background level is then 15-21 e-/pix.The Hill sphere of new active asteroid P/2018 P3 at high resolutionWe request 3 orbits of DD time to study the newly discovered active asteroid P/2018 P3 at superb spatial resolution (<30km) of its Hill sphere. This resolution is facilitated by the asteroid's close perigee passage in late September, and will enable us to perform a sensitive search for both indications of a wide binary system, and gravitationally unbound fragments resulting from a (near-)catastrophic collision. The results will help us to constrain the process behind the activity of P3. We will also study the 3-dimensional motion of dust from P3, putting additional constraint on the type of activity. The processes triggering and sustaining asteroid activity are currently not well understood, but they are likely the same that drive the evolution and comminution of the asteroid population at large. Opportunities to resolve the Hill sphere of an active asteroid are rare, and the next such opportunity for P3 will only arise in 2023. Comparably favourable circumstances led to the discovery of the first known wide binary system with similarly sized components (288P) in 2016. It is subject to on-going research if the previously unobserved special configuration of 288P has been shaped by its activity or if the two are independent phenomena. The proposed observations can help to resolve this question.We observe active asteroid P3 during 3 visits of 1 orbit each between September and December 2018. The first visit should be scheduled as soon as possible to catch P3 near perihelion (October 08) and perigee (September 21). The second visit should be scheduled about two weeks after the first to study the motion of potential fragments or a binary system. Both these observations will be obtained while the Earth is above the orbital plane of P3. In order to study the 3D distribution of dust, constrain the orbit of a potential binary system, and measure the motion of potential slow and unbound fragments, the third visit should be scheduled well after the Earth's plane crossing on November 22, but while still a reasonable resolution of the Hill sphere can be obtained. The optimum time for visit 3 is therefore late December (plane angle ~-3.5deg, pixel scale ~44 km).
The predicted total magnitude of P3 is V=19.7 in late September, decreasing to 21.5 by late December. We expect that the nucleus or largest fragment will be 1-2 mag fainter, V = 22 - 23.
The orbital visibility for a solar system target near the ecliptic plane is 54 min (Section 6.3 of the HST Primer document). In each orbit, we will take 8 exposures of ~225s using the 1k subarray of WFC3. For the three single orbits we will perform a subsampling dither box pattern, obtaining 2 exposures at each dither point. We will carefully drizzle our subsampled images to a finer output pixel scale to extract the extra spatial information gathered by our subsampling strategy. This enhanced resolution will allow us to determine the relative position of fragments or binary components at the highest possible accuracy. The dithering will also enable us to reject hot pixels and cosmic ray hits.
This strategy gives us a total exposure time of 1800s = 30min per orbit, and estimated overheads of 6min for guide-star acquisition, 2.6min for the first exposure, a total of 14.7min for the subsequent 7 exposures, and 1.5min for the three spacecraft maneuvers required for dithering, which adds up to a total execution time of 54min per orbit.
We will use the wide bandpass filter F606W for an optimum trade-off between sensitivity and highest resolution: the bandpass (475 - 700 nm) covers the maximum of the solar spectrum, and is in the wavelength range where the PSF is smallest (FWHM<0.07arcsec, from the WFC3 instrument handbook for Cycle 26), such that we can optimally exploit our subsampling dither strategy.
The WFC3 exposure time calculator returns for a solar-spectrum point source at V=22, exposure time of 225s, F606W filter, and default background values a signal-to-noise-ratio (S/N) of 80 within a circle of 0.08arcsec (ETC Request ID: WFC3UVIS.im.1285904). The small aperture is needed to separate the flux from the nucleus or fragment from that of the surrounding coma. A fragment with V=26 will be detected at S/N=8 (WFC3UVIS.im.1285906), such that we expect to detect fragments down to 180m diameter for standard assumptions on a C-type asteroid with geometric albedo p=0.06 \citep (Nugent et al., 2016) and phase function coefficient G=0.15 (Bowell et al. 1989).
The position uncertainty predicted for P3 at the end of September is currently large. However, continuing astrometry of this bright object will reduce this error to ~1arcsec by the time of the proposed first visit.
The maximum apparent motion of P3 is only ~25 arcsec/hr (0.0069 arcsec/s), which is well within Hubble's tracking capabilities.Solar System0falseSUPPORTEDSOLAR SYSTEMCOMETCOMET P/2018 P3TYPE=COMET,Q=1.756991698115274,E=0.4160241687876102,I=8.910116391330794
,O=59.2365710289956,W=305.7892364559521,T=09-OCT-2018:07:56:52,TTimeScale=TDB,EQUINOX=J2000,EPOCH=22-AUG-2018:00:00:00,EpochTimeScale=TDBEARTHSOLAR SYSTEMCOMETCOMET P/2018 P3TYPE=COMET,Q=1.756522583690934,E=0.4158611818158186,I=8.909229937235208
,O=59.21252717415003,W=305.8681459350315,T=09-OCT-2018:10:25:23,TTimeScale=TDB,EQUINOX=J2000,EPOCH=18-SEP-2018:00:00:00,EpochTimeScale=TDBEARTHSOLAR SYSTEMCOMETCOMET P/2018 P3TYPE=COMET,Q=1.756522583690934,E=0.4158611818158186,I=8.909229937235208
,O=59.21252717415003,W=305.8681459350315,T=09-OCT-2018:10:25:23,TTimeScale=TDB,EQUINOX=J2000,EPOCH=18-SEP-2018:00:00:00,EpochTimeScale=TDBEARTHWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF606WPOS-TARGDITHER0.173LINE0.112falsefalse81.785423.884WFC3-UVIS-DITHER-BOX1falseUsing ephemeris for target 15623-01-P2018P3ephemeris data for target 15623-01-P2018P3 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 18.240 to 20.090. ephemeris interval: 18.304 to 20.306The scheduling data was generated by CASM 26.2.CASM was run in Phase II mode./tmp/OPVisit3005317068090944860.xml153815791700038.76076331085659(Tic-Visit
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)true10The FLASH level warning disappears if the ETC is run with the zodiacal light calculated for the specific sky position and time (30 Sep). The background level is then 15 e-/pix (ETC request WFC3UVIS.im.1287993).Using ephemeris for target 15623-02-P2018P3V2ephemeris data for target 15623-02-P2018P3V2 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 18.240 to 20.090. ephemeris interval: 18.304 to 20.306The scheduling data was generated by CASM 26.2.CASM was run in Phase II mode./tmp/OPVisit12792091143254597293.xml154222544500060.2537201102823(Tic-Visit
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)true10The FLASH level warning disappears if the ETC is run with the zodiacal light calculated for the specific sky position and time (15 Oct). The background level is then 15 e-/pix (ETC request WFC3UVIS.im.1287994).Using ephemeris for target 15623-03-P2018P3V3ephemeris data for target 15623-03-P2018P3V3 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 18.240 to 20.090. ephemeris interval: 18.304 to 20.306The scheduling data was generated by CASM 26.2.CASM was run in Phase II mode./tmp/OPVisit16976501407941656651.xml(Tic-Visit
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)true10The FLASH level warning disappears if the ETC is run with the zodiacal light calculated for the specific sky position and time (25 Dec). The background level is then 21 e-/pix (ETC request WFC3UVIS.im.1287995).