0 Assigned ID: 543 ----- Attempting Submission 1 (Fri Apr 10 16:10:47 GMT 2015) ----- 0 0 ----- Attempting Submission 1 (Thu Jul 23 11:01:14 GMT 2015) ----- HST Phase II Proposal 14169 (GO14169_P2_v4.apt) successfully submitted. Receipt: # 14169-1 ----- Attempting Submission 2 (Mon Dec 21 16:07:00 GMT 2015) ----- Over the past few years, observations of close-in giant planet atmospheres using WFC3's spectroscopic capabilities have played a pivotal role in the NIR characterization of these worlds. We propose to build upon this success by measuring H2O in the atmosphere of the warm Saturn-mass exoplanet WASP-39b. Our previous optical STIS observations have revealed that WASP-39b has a cloud and haze-free atmosphere, implying that a strong H2O signal will be detectable. Combined with the scattering signature due to H2 that we have measured at shorter wavelengths, our detection will enable us to determine the absolute H2O abundance of the atmosphere. This information is extremely valuable, as it helps to constrain the formation and evolutionary history of the planet, such as the composition of the primordial accretion disk and the planet's location within that disk. Very few H2O abundance measurements for transiting exoplanets are currently available, fewer in which the interpretation is not hindered by clouds or hazes. As such, with a clear atmosphere WASP-39b is uniquely placed to provide an important constraint on its atmospheric chemical abundances. We will use WFC3/IR spectroscopic grism G102 to observe WASP-39 from 0.8 - 1.15 microns over one transit event, with a visit consisting of five consecutive HST orbits. Three orbits will be used to determine the baseline flux, one before and one after transit, while one or two occur during the transit event. We will repeat our successful observing strategies for WFC3 in which we have now perfected very high S/N transit observations in the NIR using spatial scan mode (GO 12473 - Wakeford et al. 2013; Sing et al. 2013; Sing, Wakeford et al. 2015.). During spatial scan mode the telescope is slowly slewed in the cross-dispersion direction while the camera is exposing. This causes the spectra to become spread over a large pixel area of the detector, providing very high S/N levels and vastly improved duty cycles. Spatial scan mode can result in a ten-fold increase in the number of photons per exposure while considerably reducing overheads. This also increases the time of saturation of the brightest pixels, and allows for longer exposure times (McCullough 2011). We also have no roll restrictions, which further eases scheduling. Using the visit planner in APT, we find that WASP-39 has very long yearly observable windows spread throughout the year. For each visit with WFC3 we will use the same observing strategy as our Cycle-19 large program GO-12473, which uses spatial scanning mode to dramatically decrease observational overheads and obtain vastly higher S/N levels. Using WFC3 G141 grism we will observe WASP-39b using spatial scan mode obtaining spectra from 1.1 - 1.7 microns. To reach precisions similar to that of previous HST observations we would require exposure times around 120 seconds spreading the light over around20 pixels with a scan rate of around 0.2 pixels per second, similar to that of XO-1 (V mag = 11.2) and WASP-31 (V mag = 11.7), which are slightly brighter than WASP-39 (V mag = 12.1). This will allow us to achieve S/N levels of around 1300 per exposure when binned up to 4 pixels with roughly 50 in transit exposures with overheads. Using a 256x256 subarray we will avoid systematics observed in the 512x512 subarray (e.g. WASP-17 Mandell, et al., 2013, GJ 1214 Berta et al., 2012), which have time dependent effects on the detector response and persistent ramp-like effects on the data (Swain et al. 2012). Using spatial scan mode instead of stare mode we will also be able to increase the number of observed photons without reaching the non-linearity limit of the detector. EXTRA-SOLAR PLANETS 12 false false false false SUPPORTED STAR EXTRA-SOLAR PLANETARY SYSTEM This object was generated by the target selector and retrieved from the SIMBAD database. WASP-39 J2000 J2000 WFC3/IR Spectroscopic No No G141 /private/var/folders/40/92b_z0vs47d8vvswm3fff72hjyfrp0/T/OPVisit3448721470093982497.xml 1450708957314 The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. transit of WASP-39b, it is essential that the 5 orbits be scheduled in a continuous block (Tic-Visit :proposal-id 14169 :visit-id "01" :proposal-version -1 :trans-version "20150609" :date "21-Dec-2015 09:42:32.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 710496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14169 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14169 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2836 :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 3210 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14169 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2951 :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 3210 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14169 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2951 :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 3210 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14169 :visit-id "01" :orbit-number 4 :pcs-time 222 :si-vis-utilization 2951 :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 3210 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14169 :visit-id "01" :orbit-number 5 :pcs-time 222 :si-vis-utilization 2951 :al-overhead-at-end 0 :internal-dur-at-end 449 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3210 :pcs-gap 0 ) true 5 0 Direct image for wavelength calibration. Phase constrained so transit occurs in orbit 3-4 between 2nd and 3rd contact. SPATIAL SCAN. Count level/pixel is estimated to be 19,444 DN from the ETC, following ISR WFC3-2012-08, with a scan rate of 0.025"/sec covering a total of ~2.8".