WASP-12 is the hottest and the largest currently known transiting exoplanet. It has the shortest orbital period and is the closest to its host star. Previous spectacular HST observations revealed that the atmosphere of HD 209458b appears to be evaporating away, though this interpretation has recently been questioned. We propose ultraviolet observations of WASP-12 to learn whether it is in a state of hydrodynamic `blow-off' as the work on HD 209458b would suggest. We will obtain a precise radius for the planet, free from systematic errors caused by the earth's atmosphere. We will use our data to hone models of exoplanet atmospheres.

We will take time-series spectroscopy with the COS/NUV TIMETAG mode using G285M at the 2676 setting, chosen to cover the Mg II 2800 A triplet. Using the COS ETC, we estimate that we will obtain a S/N between 11 and 7 in 120 sec (spectrum binned to 1 A). TIMETAG observing mode will allow us to flexibly bin our spectrum in wavelength and/or time to address different science questions. We require two visits, each with five orbits to fuly cover all four contact points and to cover the pre and post transit phases. The HST visibility window for WASP-12 is 54 mi. The observations need to be made at tightly specified phase intervals in order to cover the entire exoplanet transit. EXTRA-SOLAR PLANETS 12 false 0.0 0.0 false false false false false false SUPPORTED STAR EXTRA-SOLAR PLANET Coordinates from USNO-B1.0 catalog. B=12.1 R=11.2. Coordinates have been rounded. J2000 06 30 0.0000 +29 40 0.00 J2000 COS/NUV Spectroscopic No No G285M 2676 COS/NUV Spectroscopic No No G285M 2676 Phase windows are not calculated when the period is less than 7.0 days. Assuming no scheduling restrictions for Phase 0.854/0.856. The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1253816234000 273.61169819282725 (Tic-Visit :proposal-id 11651 :visit-id "01" :proposal-version -1 :trans-version "20080609" :date "30-Jun-2008 09:56:51.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "32" :si-bright-earth-limb-angle 20.0 :data-volume 269760 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11651 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11651 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2934 :al-overhead-at-end 0 :internal-dur-at-end 78 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11651 :visit-id "01" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3072 :al-overhead-at-end 0 :internal-dur-at-end 88 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11651 :visit-id "01" :orbit-number 3 :pcs-time 195 :si-vis-utilization 3072 :al-overhead-at-end 0 :internal-dur-at-end 88 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11651 :visit-id "01" :orbit-number 4 :pcs-time 195 :si-vis-utilization 3072 :al-overhead-at-end 0 :internal-dur-at-end 88 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11651 :visit-id "01" :orbit-number 5 :pcs-time 195 :si-vis-utilization 3072 :al-overhead-at-end 0 :internal-dur-at-end 400 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) false 5 0 ETC ID #COS69602 gives t_exp=15.6 sec for S/N = 40 in NUV imaging PSA/MIRRORB for a G0 V star with B=12.1. ETC ID #COS69602 gives t_exp=15.6 sec for S/N = 40 in NUV imaging PSA/MIRRORB for a G0 V star with B=12.1. Buffer time recommended by ETC (run ID #COS9176) is 8091 sec. Multiplied by 2/3 for safety gives 5394 sec. I rounded down to 5000 sec since we're well over an orbit anyway. Phase windows are not calculated when the period is less than 7.0 days. Assuming no scheduling restrictions for Phase 0.828/0.830. The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 11651 :visit-id "02" :proposal-version -1 :trans-version "20080609" :date "30-Jun-2008 09:56:57.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "32" :si-bright-earth-limb-angle 20.0 :data-volume 269760 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11651 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11651 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2934 :al-overhead-at-end 0 :internal-dur-at-end 78 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11651 :visit-id "02" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3072 :al-overhead-at-end 0 :internal-dur-at-end 88 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11651 :visit-id "02" :orbit-number 3 :pcs-time 195 :si-vis-utilization 3072 :al-overhead-at-end 0 :internal-dur-at-end 88 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11651 :visit-id "02" :orbit-number 4 :pcs-time 195 :si-vis-utilization 3072 :al-overhead-at-end 0 :internal-dur-at-end 88 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11651 :visit-id "02" :orbit-number 5 :pcs-time 195 :si-vis-utilization 3072 :al-overhead-at-end 0 :internal-dur-at-end 400 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) false 5 0 ETC ID #COS69602 gives t_exp=15.6 sec for S/N = 40 in NUV imaging PSA/MIRRORB for a G0 V star with B=12.1. ETC ID #COS69602 gives t_exp=15.6 sec for S/N = 40 in NUV imaging PSA/MIRRORB for a G0 V star with B=12.1. Buffer time recommended by ETC (run ID #COS9176) is 8091 sec. Multiplied by 2/3 for safety gives 5394 sec. I rounded down to 5000 sec since we're well over an orbit anyway.