Uranus is now past its 7 December 2007 equinox. The large seasonal phase shift expected from its long radiative time constant implies that it should now be in the process of reversing its hemispheric asymmetries in cloud band structure and zonal circulation. Many changes already observed -- the development of the first visible-wavelength dark spot, discovered in Cycle 15, the fading of the south polar cap, and the development of a new northern bright band while the southern band fades -- may all be indicative of the expected reversal. We propose a detailed characterization of Uranus' current seasonal response with a 9-orbit program consisting of 3 orbits of WFC3 imaging of cloud bands and dark spots, and 6 orbits of high signal-to-noise imaging using the F845M filter, capable of tracking bright discrete cloud features. Filters between 0.467 and 1.7 microns will provide vertical sensing depths scanning through the pressure range where the putative methane and deeper H2S clouds might plausibly exist and provide strong constraints on their contributions and parent gas mixing ratios. These observations have unique combinations of spectral range and resolution with needed temporal sampling and spatial resolution not available from groundbased observations.

The F547M, F658N, and F763M filters are very similar to the ACS filters that revealed the dark spot we discovered in Cycle 15, which displayed maximum contrast at 658 nm. The F467M filter is one that provided the highest contrast for dark spots on Neptune. The F763M and F845M will provide high contrast for bright features. After redesign of the observing program (which initially used NICMOS for high-contrast imaging of bright features), this burden falls to the F845M filter. Though feature contrast is reduced in the F845M (compared to the F160W) bandpass, high signal-to-noise ratios and coadding of de-rotated images will make up for the loss of contrast. Additionally, the F845M filter is superior to filters used previously for feature tracking on ACS and WFPC2, due to its sampling the methane window near 830 nm with less Rayleigh scattering than in the F775W filter, and higher throughput allowing exposures one quarter the duration needed for F850LP exposures (35s vs 140s). The FQ889N, FQ906N, FQ924N, and FQ937N filters will probe a range of atmospheric depths that will be comparable to those of the ramp filter observations we obtained with ACS in Cycle 15 (ranging from < 1 bar to > 10 bars in a clear atmosphere), and mainly used for constraining models of vertical structure of cloud bands. The WFC3/IR F160W filter is also aimed at improving our models for the vertical structure of cloud bands. Unfortunately the pixel scale of the WFC3/IR array (0.13 arcsecond/pixel) precludes its use as the primary camera for feature tracking. The 9-orbit observing program is designed to obtain (1) complete longitudinal coverage for the F845M and F658N filters at 60 N for detection of new bright cloud features (which were discovered in 2007) and high-latitude dark features, and (2) nearly complete repeated coverage to obtain accurate zonal cloud motions. Orbits 1, 4, 6, and 19 (orbits relative to first (which is Orbit 1)) provide the base longitude coverage for the high-contrast F845M imaging program. Two additional orbits (16 and 21) provide important temporal coverage that, with other images, allows dynamical measurements of latitudinal and longitudinal motions over the 15-30 hour time domain that is inaccessible from the ground. The remaining WFC3 sampling provides complete longitudinal coverage for key filters at 30 N, where previously discovered dark spots have been seen. This can be done with only three orbits (2, 5, and 20), because of more favorable viewing. Lower latitudes provide even better coverage. The large sampling gap (between orbits 6 and 16) is needed to avoid SAA interference. The coverage varies with latitude because of view angle differences and differences in planetary rotation rates. Dynamical information on longer time scales will be obtained from analysis combining any 2009 groundbased observations that are acquired, and from SNAP images acquired. Our coverage objectives for these WFC3 images are designed to obtain center-to-limb information for deciphering the vertical structure of latitude bands, as well as providing the coverage needed for detection of dark spots. SOLAR SYSTEM 12 false 0.0 0.0 false false false false false false SUPPORTED SOLAR SYSTEM PLANET PLANET URANUS STD=URANUS NOT TRANSIT OF ARIEL ACROSS URANUS FROM EARTH, NOT TRANSIT OF UMBRIEL ACROSS URANUS FROM EARTH, NOT TRANSIT OF TITANIA ACROSS URANUS FROM EARTH, NOT TRANSIT OF OBERON ACROSS URANUS FROM EARTH, NOT TRANSIT OF MIRANDA ACROSS URANUS FROM EARTH EARTH NIC1 Imaging No No F095N NIC1 Imaging No No F097N NIC1 Imaging No No F108N NIC1 Imaging No No F160W NIC1 Imaging No No F170M NIC2 Imaging No No F187N WFC3/UVIS Imaging No No F467M WFC3/UVIS Imaging No No F658N WFC3/UVIS Imaging No No FQ727N WFC3/UVIS Imaging No No FQ750N WFC3/UVIS Imaging No No FQ889N WFC3/UVIS Imaging No No FQ906N WFC3/UVIS Imaging No No FQ924N WFC3/UVIS Imaging No No FQ937N WFC3/UVIS Imaging No No FQ619N WFC3/UVIS Imaging No No F547M WFC3/UVIS Imaging No No F658N WFC3/UVIS Imaging No No F763M WFC3/UVIS Imaging No No F845M WFC3/UVIS Imaging No No FQ889N WFC3/UVIS Imaging No No FQ906N WFC3/UVIS Imaging No No FQ924N WFC3/UVIS Imaging No No FQ937N POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 1 false POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 2 false POS-TARG DITHER 0.636 LINE false false 2 41.788 WFC3-IR-DITHER-LINE 3 false Using ephemeris for target 11573-01-URANUS ephemeris data for target 11573-01-URANUS does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 08.306 to 11.001. ephemeris interval: 09.181 to 11.182 Timing link suitability includes constraints ([02 After 01 by 0.1 to 0.1 days] [04 After 01 by 0.2 to 0.2 days] [05 After 01 by 0.3 to 0.3 days] [06 After 01 by 0.3 to 0.3 days] [16 After 01 by 1.0 to 1.0 days] [19 After 01 by 1.2 to 1.2 days] [20 After 01 by 1.3 to 1.3 days] [21 After 01 by 1.3 to 1.3 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1257944880000 83.18472176397142 (Tic-Visit :proposal-id 11573 :visit-id "01" :proposal-version -1 :trans-version "20090130" :date "02-Jul-2009 08:09:36.0" :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 227792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2774 :al-overhead-at-end 0 :internal-dur-at-end 287 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) false 1 0 Using ephemeris for target 11573-02-URANUS ephemeris data for target 11573-02-URANUS does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 08.306 to 11.001. ephemeris interval: 09.181 to 11.182 Timing link suitability includes constraints ([02 After 01 by 0.1 to 0.1 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1257950632000 83.35701016960871 (Tic-Visit :proposal-id 11573 :visit-id "02" :proposal-version -1 :trans-version "20090130" :date "02-Jul-2009 08:09:39.0" :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 431856 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2835 :al-overhead-at-end 0 :internal-dur-at-end 510 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) false 1 0 Using ephemeris for target 11573-04-URANUS ephemeris data for target 11573-04-URANUS does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 08.306 to 11.001. ephemeris interval: 09.181 to 11.182 Timing link suitability includes constraints ([04 After 01 by 0.2 to 0.2 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1257962138000 83.18491609907801 (Tic-Visit :proposal-id 11573 :visit-id "04" :proposal-version -1 :trans-version "20090130" :date "02-Jul-2009 08:09:44.0" :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 227792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2774 :al-overhead-at-end 0 :internal-dur-at-end 287 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) true 1 0 Using ephemeris for target 11573-05-URANUS ephemeris data for target 11573-05-URANUS does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 08.306 to 11.001. ephemeris interval: 09.181 to 11.182 Timing link suitability includes constraints ([05 After 01 by 0.3 to 0.3 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1257967890000 77.82278913210598 (Tic-Visit :proposal-id 11573 :visit-id "05" :proposal-version -1 :trans-version "20090130" :date "02-Jul-2009 08:09:46.0" :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 370560 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2798 :al-overhead-at-end 0 :internal-dur-at-end 443 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) true 1 0 Using ephemeris for target 11573-06-URANUS ephemeris data for target 11573-06-URANUS does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 08.306 to 11.001. ephemeris interval: 09.181 to 11.182 Timing link suitability includes constraints ([06 After 01 by 0.3 to 0.3 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1257973643000 83.18504471381078 (Tic-Visit :proposal-id 11573 :visit-id "06" :proposal-version -1 :trans-version "20090130" :date "02-Jul-2009 08:09:49.0" :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 227792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "06" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2774 :al-overhead-at-end 0 :internal-dur-at-end 287 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) true 1 0 Using ephemeris for target 11573-16-URANUS ephemeris data for target 11573-16-URANUS does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 08.306 to 11.001. ephemeris interval: 09.181 to 11.182 Timing link suitability includes constraints ([16 After 01 by 1.0 to 1.0 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1258031168000 83.18567646106482 (Tic-Visit :proposal-id 11573 :visit-id "16" :proposal-version -1 :trans-version "20090130" :date "02-Jul-2009 08:09:55.0" :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 227792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "16" :obset-id "16" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "16" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2774 :al-overhead-at-end 0 :internal-dur-at-end 287 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) true 1 0 Using ephemeris for target 11573-19-URANUS ephemeris data for target 11573-19-URANUS does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 08.306 to 11.001. ephemeris interval: 09.181 to 11.182 Timing link suitability includes constraints ([19 After 01 by 1.2 to 1.2 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1258048425000 66.2189726053372 (Tic-Visit :proposal-id 11573 :visit-id "19" :proposal-version -1 :trans-version "20090130" :date "02-Jul-2009 08:09:59.0" :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 227792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "19" :obset-id "19" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "19" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2774 :al-overhead-at-end 0 :internal-dur-at-end 287 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) true 1 0 Using ephemeris for target 11573-20-URANUS ephemeris data for target 11573-20-URANUS does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 08.306 to 11.001. ephemeris interval: 09.181 to 11.182 Timing link suitability includes constraints ([20 After 01 by 1.3 to 1.3 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1258054177000 68.27942618230571 (Tic-Visit :proposal-id 11573 :visit-id "20" :proposal-version -1 :trans-version "20090130" :date "02-Jul-2009 08:10:01.0" :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 370560 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "20" :obset-id "20" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "20" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2798 :al-overhead-at-end 0 :internal-dur-at-end 443 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) true 1 0 Using ephemeris for target 11573-21-URANUS ephemeris data for target 11573-21-URANUS does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 08.306 to 11.001. ephemeris interval: 09.181 to 11.182 Timing link suitability includes constraints ([21 After 01 by 1.3 to 1.3 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1258059930000 74.97689920239799 (Tic-Visit :proposal-id 11573 :visit-id "21" :proposal-version -1 :trans-version "20090130" :date "02-Jul-2009 08:10:06.0" :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 227792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "21" :obset-id "21" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "21" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2774 :al-overhead-at-end 0 :internal-dur-at-end 287 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) true 1 0 (Tic-Visit :proposal-id 11573 :visit-id "22" :proposal-version -1 :trans-version "20100218" :date "22-Mar-2010 08:09:43.0" :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 431856 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "22" :obset-id "22" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "22" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2710 :al-overhead-at-end 0 :internal-dur-at-end 510 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) false 1 0 Exposure cut from 15.5s to 14.1 so visit could schedule. Exposure cut from 140s to 127 so the visit could schedule. Exposure cut from 240s to 218 so the visit could schedule. Exposure cut from 60s to 55s so the visit could schedule. Exposure cut from 140s to 127s so the visit could schedule. Exposure cut from 330s to 300s so the visit could schedule. Exposure cut from 280s to 255s so the visit could schedule. Exposure cut from 180s to 164s so the visit could schedule. (Tic-Visit :proposal-id 11573 :visit-id "05" :proposal-version -1 :trans-version "20090130" :date "02-Jul-2009 08:09:46.0" :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 370560 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2798 :al-overhead-at-end 0 :internal-dur-at-end 443 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) false 1 0 Exposure cut from 144s to 135s so the visit could schedule. Exposure cut from 6s to 5.6 so the visit could schedule. Exposure cut from 160s to 150s so the visit could schedule. Exposure cut from 26s to 24.4 so the visit could schedule. Exposure cut from 35s to 32.9s so the visit could schedule. Exposure cut from 180s to 169s so the visit could schedule. Exposure cut from 300s to 282s so the visit could schedule. Exposure cut from 360s to 338s so the visit could schedule. Exposure cut from 140s to 132s so the visit could schedule. (Tic-Visit :proposal-id 11573 :visit-id "20" :proposal-version -1 :trans-version "20090130" :date "02-Jul-2009 08:10:01.0" :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 370560 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11573 :visit-id "20" :obset-id "20" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11573 :visit-id "20" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2798 :al-overhead-at-end 0 :internal-dur-at-end 443 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) false 1 0 Exposure cut from 144s to 135s so the visit could schedule. Exposure cut from 6s to 5.6 so the visit could schedule. Exposure cut from 160s to 150s so the visit could schedule. Exposure cut from 26s to 24.4 so the visit could schedule. Exposure cut from 35s to 32.9s so the visit could schedule. Exposure cut from 180s to 169s so the visit could schedule. Exposure cut from 300s to 282s so the visit could schedule. Exposure cut from 360s to 338s so the visit could schedule. Exposure cut from 140s to 132s so the visit could schedule.