Characterising the dust ejection process in the first known active binary asteroid system 288P/300163.

0 Assigned ID: 1252 ----- Attempting Submission 1 (Thu Sep 29 18:41:47 GMT 2016) ----- 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 browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser Added CR-SPLIT=NO -219281950 ----- Attempting Submission 1 (Wed Nov 23 21:33:22 GMT 2016) ----- ----- Attempting Submission 2 (Tue Nov 29 08:09:29 GMT 2016) ----- We have checked that the flash level warnings go away when running the exposure time calculator with the zodiacal light backgroudn calculated for 2017, January 15 instead of the generic low level assumed by the APT. Previous observations from programs 14790 and 14864 using the same settings and target are of high quality. Characterising the dust ejection process in the first known active binary asteroid system 288P/300163. We request four orbits of MC time to monitor the dust ejected from the recently discovered, first known active binary asteroid system 288P/300163, using WFC3. The key aim is to trace the influence of the binary nature and/or potential rapid rotation on the sublimation-driven activity, in order to understand if the activity was triggered by the same process that led to the formation of the binary, or if the two processes were independent. Both dust release and binary formation can be a consequence of rapid rotation, and 288P is the first object showing both these phenomena, which may emphasise the importance of the YORP-effect in re-shaping the asteroid belt. The proposed observations will exploit the change in projection related to the Earth's crossing the orbital plane of 288P in 2016 December to reconstruct the three-dimensional distribution of the dust ejected from the 288P system. As this coincides with the expected maximum of activity (perihelion is on November 08) and a close approach to Earth (perigee was on September-10 at 1.45 AU), we will follow the dust ejection process at supreme temporal and spatial resolution. The activity of 288P is expected to cease around 2017 February, which triggers our request for mid-cycle time. The purpose of the program is to observe active asteroid 288P during December 2016 through February 2017. One orbit should be scheduled as close a possible to December 14 in order to measure the vertical extent of the dust trail while the Earth crosses the orbital plane of 288P. The remaining 3 orbits should be spaced at 2-3 week intervals and before 288P enters the solar exclusion zone in mid-February. This will give us three high-resolution measurements of the dust sheet from a perspective south of the orbital plane, complementary to our existing observations (from GO 14790 and GO 14864) obtained from a northern perspective. The three measurements will allow us to sufficiently sample the temporal evolution of the dust tail and coma to distinguish between episodic and continuous emission. We will follow the same successful observation strategy as for our programs GO 14790 and 14864, ensuring a maximum comparability of the data. 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 $\sim$230\,s using the 1k subarray of WFC3. We will perform a subsampling dither box pattern, obtaining 2 exposures at each dither point. We will carefully drizzle our subsampled images to a finer output pixel scale to extract the extra spatial information gathered by our subsampling strategy. This enhanced resolution will allow us to extract the maximum possible information on the two nuclei and the dust distribution in the innermost coma. The dithering will also enable us to reject hot pixels and cosmic ray hits. This strategy gives us a total exposure time of 1840\,s = 30min per orbit, and estimated overheads of 6\,min for guide-star acquisition, 2.6\,min for the first exposure, a total of 14.7\,min for the subsequent 7 exposures, and 1.5\,min for the three spacecraft maneuvers required for dithering, which adds up to a total execution time of 54\,min per orbit. Our observations of GO 14790 and 14864 show that this exposure time is adequate to detect the dust tail at good S/N. We will use the wide bandpass filter F606W for an optimum trade-off between sensitivity and highest resolution: the bandpass (475 -- 700 nm) covers the maximum of the solar spectrum, and is in the wavelength range where the PSF is smallest (FWHM$<$0.07 arcsec, from the WFC3 instrument handbook for Cycle 24), such that we can optimally exploit our subsampling dither strategy. In addition, F606W is the same filter we used to observe 288P in GO 12597, 14790 and 14864, enabling a direct comparison of the data sets. Solar System 3 false false false false false false SUPPORTED SOLAR SYSTEM YES COMET active asteroid TYPE=COMET,Q=2.437997636061935,E=.2002773126787514,I=3.239254302184838,O=83.22502588733704,W=281.9669249151093,T=18-JUL-2011:22:51:20,TTimeScale=UTC,EQUINOX=J2000,EPOCH=19-JUN-2010:00:00:00,EpochTimeScale=TDB EARTH WFC3/UVIS Imaging No No F606W WFC3/UVIS Imaging No No F606W WFC3/UVIS Imaging No No F606W WFC3/UVIS Imaging No No F606W POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 1

false

1479935385121 Using ephemeris for target 14884-01-288P ephemeris data for target 14884-01-288P does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 16.214 to 18.089. ephemeris interval: 16.305 to 18.305 The scheduling data was generated by CASM 24.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14884 :visit-id "01" :proposal-version -1 :trans-version "20160601" :date "23-Nov-2016 22:09:44.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 142608 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14884 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14884 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2674 :al-overhead-at-end 0 :internal-dur-at-end 192 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3210 :pcs-gap 0 ) false 1 0 1479935381132 Using ephemeris for target 14884-02-288P ephemeris data for target 14884-02-288P does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 16.214 to 18.089. ephemeris interval: 16.305 to 18.305 The scheduling data was generated by CASM 24.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14884 :visit-id "02" :proposal-version -1 :trans-version "20160601" :date "23-Nov-2016 22:09:40.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 142608 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14884 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14884 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2674 :al-overhead-at-end 0 :internal-dur-at-end 192 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3210 :pcs-gap 0 ) false 1 0 1479935376809 Using ephemeris for target 14884-03-288P ephemeris data for target 14884-03-288P does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 16.214 to 18.089. ephemeris interval: 16.305 to 18.305 The scheduling data was generated by CASM 24.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14884 :visit-id "03" :proposal-version -1 :trans-version "20160601" :date "23-Nov-2016 22:09:36.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 142608 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14884 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14884 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2674 :al-overhead-at-end 0 :internal-dur-at-end 192 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3210 :pcs-gap 0 ) false 1 0 1480406829771 /tmp/OPVisit2193132840859385759.xml Using ephemeris for target 14884-04-288P ephemeris data for target 14884-04-288P does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 16.214 to 18.089. ephemeris interval: 16.305 to 18.305 The scheduling data was generated by CASM 24.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14884 :visit-id "04" :proposal-version -1 :trans-version "20160601" :date "29-Nov-2016 09:07:08.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 142608 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14884 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14884 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2674 :al-overhead-at-end 0 :internal-dur-at-end 192 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3210 :pcs-gap 0 ) true 1 0