0 Assigned ID: 776 ----- Attempting Submission 1 (Fri Apr 11 20:37:35 GMT 2014) ----- 0 Target of Opportunity Observation of an Episodic Storm on Uranus We propose a TOO observation of Uranus to capture the formation process of a dark anticyclonic vortex during an episodic convective storm. The planet Uranus continues to exhibit increased atmospheric activity after the 2007 equinox, likely in response to extreme insolation change (Hammel et al. 2005, Icarus 175, 284, Sromovsky et al. 2009, Icarus 203, 265, Sromovsky et al. 2007, Icarus 192, 558, Sromovsky et al. 2012, Icarus 220, 6). We hypothesize that Uranian dark spots emerge from an episodic outburst, and predict that such a spot will form in the near future. The historical record makes references to such discrete structures (both bright and dark) on Uranus during previous equinoctial apparitions (Alexander 1965; the last equinox occurred in 1965). Furthermore, northern high-latitudes are now coming into view after 40+ years of winter darkness, exhibiting unusual activities (Sromovsky et al. 2012, Icarus 220, 694). Our TOO will be triggered by amateur observations; the best amateur facilities are now able to resolve the disk of Uranus and detect such activity if it is very large or has very high contrast. Amateurs also have access to a great many nights of telescope time. If a discrete cloud feature on Uranus is reported through these networked professional and amateur ground-based observations, we propose to obtain follow-up images with Hubble's WFC3. The proposed TOO images will permit determination of detailed structure of the feature at visible wavelengths, and provide vertical and horizontal constraints on the feature's scattering properties. Hubble is the only facility that can provide such information at visible wavelengths. All WFC3 exposures have CR-SPLIT=NO to reduce overhead. POS-TARG offsets for quad filter WFC3 exposures have been specified to place target approximately 20 arcseconds closer to center of array relative to "optimal" aperture locations. This places the planet approximately 10 arcseconds towards the center of the array relative to the "QUAD-FIX" fiducial points. This has been done to reduce telescope move magnitudes (between different quads), while still leaving a 512 x 512 pixel area around the target outside of the quad filter vignetted regions. We request three orbits of WFC3 imaging to obtain disk-resolved images of an anomalous feature on Uranus. The three orbits will be timed such that all 360-degree of longitudes are captured in the shortest time possible allowed within applicable scheduling constraints. We use an identical set of filters for all three orbits to obtain a consistent coverage across longitudes. We use the following filters; the strong methane absorption band near 889 nm as well its neighboring continuum at 937 nm; the intermediate methane absorption band at 727 nm and the corresponding continuum at 750 nm; weak methane absorption band at 619nm; filters corresponding to Stromgren b (467 nm) and y (547 nm) filters used for long-term brightness monitoring; and the F658N filter similar to one that showed maximum contrast for the Uranus dark spot in C15. In general, we will not dither due to short exposure times (dithering imposes a 2.5-min penalty for splitting the exposure, and dithering several exposures could require a 5.6-min buffer readout). If there is time remaining in an orbit in Phase II planning, we will dither additional F845M and F924N exposures to increase S/N and better sample the point spread function in this filter as done in our 2011 TOO observations. We will use sub-arrays to avoid the need for buffer readouts during our planned visits. Comparisons with images at nearby wavelengths will permit identification of artifacts and cosmic rays. SOLAR SYSTEM 0 false false false false false SUPPORTED SOLAR SYSTEM PLANET URANUS STD=URANUS EARTH WFC3/UVIS Imaging No No F467M WFC3/UVIS Imaging No No F547M WFC3/UVIS Imaging No No FQ619N WFC3/UVIS Imaging No No F658N WFC3/UVIS Imaging No No FQ727N WFC3/UVIS Imaging No No FQ750N WFC3/UVIS Imaging No No F775W WFC3/UVIS Imaging No No F845M WFC3/UVIS Imaging No No FQ889N WFC3/UVIS Imaging No No FQ924N WFC3/UVIS Imaging No No FQ937N Timing link suitability includes constraints ([02 After 01 by 0.2 to 0.3 days] [03 After 01 by 0.4 to 0.5 days]) The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. /solaris/user1/mlink/work/OP-cache/13712-v01.xml 50.0 (Tic-Visit :proposal-id 13712 :visit-id "01" :proposal-version -1 :trans-version "20140605" :date "30-Sep-2014 10:43:53.0" :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 369408 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13712 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13712 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2667 :al-overhead-at-end 0 :internal-dur-at-end 440 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3000.0 :pcs-gap 0 ) false 1 0 For Target of Opportunity (Non-Disruptive) Timing link suitability includes constraints ([02 After 01 by 0.2 to 0.3 days]) The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. /solaris/user1/mlink/work/OP-cache/13712-v02.xml 50.0 (Tic-Visit :proposal-id 13712 :visit-id "02" :proposal-version -1 :trans-version "20140605" :date "30-Sep-2014 10:44:05.0" :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 369408 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13712 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13712 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2667 :al-overhead-at-end 0 :internal-dur-at-end 440 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3000.0 :pcs-gap 0 ) true 1 0 For Target of Opportunity (Non-Disruptive) Timing link suitability includes constraints ([03 After 01 by 0.4 to 0.5 days]) The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. /solaris/user1/mlink/work/OP-cache/13712-v03.xml 50.0 (Tic-Visit :proposal-id 13712 :visit-id "03" :proposal-version -1 :trans-version "20140605" :date "30-Sep-2014 10:44:16.0" :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 369408 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13712 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13712 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2667 :al-overhead-at-end 0 :internal-dur-at-end 440 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3000.0 :pcs-gap 0 ) true 1 0 For Target of Opportunity (Non-Disruptive) -- Visit 3 is to happen 4 Uranus rotations (between 68 and 71 hours) after Visit 1