Marco and I fixed. still won't allow visit schedule run 1633459315 ----- Attempting Submission 4 (Wed Apr 03 17:07:12 GMT 2013) ----- ----- Attempting Submission 5 (Wed Apr 03 18:25:23 GMT 2013) ----- ----- Attempting Submission 6 (Wed Apr 03 21:37:10 GMT 2013) ----- ----- Attempting Submission 7 (Thu Apr 04 21:20:11 GMT 2013) ----- Can't get visit planner to work. We propose for Director's Discretionary time to obtain ACS/WFC polarimetric images of Comet C/2012 S1 (ISON) on its pre-perihelion approach to the inner solar system before it becomes unobservable by HST. Comet ISON is a sungrazer on a nearly parabolic trajectory, similar to that of the Great Comet of 1680, and likely carries pristine material dating to the time of the solar-system formation. Recent polarimetric observations of other comets have found that different regions of the coma produce different polarimetric light-scattering responses, indicating that different portions of the coma contain different materials. The presence of a strongly negatively polarizing circumnucleus halo region that has been observed very near the nucleus of several comets suggest a depletion of absorbing, carbonaceous particles in this region. High spatial-resolution ACS polarimetric images of Comet ISON not only can be used to place bounds on the material constituents of different regions of its coma, but can also be used to explore its dynamics and acquire an understanding of the radiation-coma interaction that accounts for coma heterogeneities. We use the ACS/WFC and the POLV* + F606W polarizer/filter combinations to measure the polarization. Instead of using CR-SPLIT, we execute two separate exposures per polarizer/filter combination. This enables us to fit the observations within two consecutive orbits, and still achieve the advantages of CR-SPLIT. SOLAR SYSTEM 0 false false false false false SUPPORTED SOLAR SYSTEM Target Ephemeris is from JPL Small-Body Database Browser. The solution date is 2013-Mar-24 20:50:46, and is JPL#20 COMET Comet C/2012 S1 (ISON) TYPE=COMET,Q=0.01250228833615271 ,E=1.000004178571949,I=61.86120174134099,O=295.7371915514632,W=345.5093083227027,T=28-NOV-2013:18:42:10,TTimeScale=TDT,EQUINOX=J2000,EPOCH=08-JAN-2013:00:00:00,EpochTimeScale=TDT EARTH ACS/WFC Imaging No No CLEAR1L POS-TARG DITHER 3.011 LINE false false 2 85.28 ACS-WFC-DITHER-LINE 1 false 1365109976333 /private/var/folders/4Y/4YzRGkiwGQWulECT4DCvLE++3Jo/-Tmp-/OPVisit4983870374772719160.xml These observations need to be made on or before May 7, 2013. However, they need to be scheduled as close to May 7 as possible. We definitely don't want them scheduled before May 6 if at all possible. (Tic-Visit :proposal-id 13199 :visit-id "01" :proposal-version -1 :trans-version "20121031" :date "04-Apr-2013 17:12:56.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 421472 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13199 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13199 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2896 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3229 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13199 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3002 :al-overhead-at-end 0 :internal-dur-at-end 190 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3229 :pcs-gap 0 ) true 2 0