Visit 01 executed with good results, but the target was very faint with no resolved nucleus or fragments so I am going with a smaller number of deeper exposures for visit 02. - Max Mutchler 1277226514 ----- Attempting Submission 1 (Wed Jun 15 19:59:52 GMT 2016) ----- ----- Attempting Submission 2 (Wed Jun 29 15:40:00 GMT 2016) ----- WFC3 imaging of active asteroid P/2016 G1 We propose to observe an active main belt asteroid, P/2016 G1 (PANSTARRS), which has been observed a few days ago with the 10m Gran Telescopio CANARIAS (GTC) telescope. GTC images show that the central condensation presents a structure similar to the X-shaped one observed in P/2010 A1, which suggest that the object is breaking apart due to some unknown mechanism. Observations with the unique high resolution and sensitivity provided by HST are urgently needed to determine which mechanism is causing the disruption: a collision of asteroids, rotational mass loss, or ice sublimation. We are requesting two HST orbits for deep WFC3 imaging at two epochs to determine the current state and early evolution of this unfolding asteroid disruption event. The first orbit (visit) should be scheduled as soon as possible, and the second visit should be scheduled 2-3 weeks later. In each orbit, we will obtain five long exposures (420s) using the broad F350LP filter for the greatest sensitivity in detecting faint fragments and dust. The multiple exposures will also allow us to reject cosmic rays, detector artifacts, and background star trails. We will include one dither shift to avoid missing data in the WFC3 interchip gap. The large WFC3 field-of-view (160x160 arcsec) helps to ensure that even with some possible pointing uncertainty (due to the non-gravitational forces involved in a disruption event) we can confidently place the target in the aperture. This observing strategy is identical to the one used successfully many times for previous active asteroid observations, and will add to a very uniform and high-quality collection of archival images of active asteroids with HST. The first visit for this program should be scheduled as soon as possible in a non-disruptive manner. The second visit is less urgent and can be scheduled 2-3 weeks later. A precise interval is not important. Solar System 0 SUPPORTED SOLAR SYSTEM YES ASTEROID Active Asteroid or Main Belt Comet TYPE=COMET,Q=2.040661899407874,E=.2100254027633657,I=10.967920669499,O=204.0747464141863,W=111.2801773466586,T=26-JAN-2017:05:23:25,TTimeScale=UTC,EQUINOX=J2000,EPOCH=18-APR-2016:00:00:00,EpochTimeScale=TDB EARTH WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP /private/var/folders/tj/27ygn_756lz3w1z19s6wtgtm0006vh/T/OPVisit5969989196232808334.xml Using ephemeris for target 14524-01-P2016-G1 ephemeris data for target 14524-01-P2016-G1 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 16.149 to 17.152. ephemeris interval: 16.152 to 18.152 Timing link suitability includes constraints ([02 After 01 by 12.0 to 22.0 days]) The scheduling data was generated by CASM 24.0. CASM was run in Phase II mode. 1467122860000 128.7021186708655 (Tic-Visit :proposal-id 14524 :visit-id "01" :proposal-version -1 :trans-version "20160322" :date "29-Jun-2016 11:32:36.0" :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 1443744 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14524 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14524 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2816 :al-overhead-at-end 0 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3210 :pcs-gap 0 ) true 1 0 /private/var/folders/tj/27ygn_756lz3w1z19s6wtgtm0006vh/T/OPVisit5386896480911065272.xml Using ephemeris for target 14524-02-P2016-G1 ephemeris data for target 14524-02-P2016-G1 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 16.149 to 17.152. ephemeris interval: 16.152 to 18.152 Timing link suitability includes constraints ([02 After 01 by 12.0 to 22.0 days]) The scheduling data was generated by CASM 24.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14524 :visit-id "02" :proposal-version -1 :trans-version "20160322" :date "29-Jun-2016 11:32:37.0" :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 1154992 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14524 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14524 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2873 :al-overhead-at-end 0 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3210 :pcs-gap 0 ) true 1 0