We are requested a fixed date observation for May the 4th. We acknowledge that this requires a quick turn around and emphasize here that we are a 100% dedicated to ensure responsiveness on our side and the success of these observations. Also, we are requesting these observations to have a proprietary period because our findings will most likely grant publication in a high-impact journal. The typical turn around between observations and such publications ranges between 4 to 6 months. Due to the high pressure that will result from our upcoming press release about the discovery of this system, we wish to prevent the requested data to be made public too early allowing the publication of quick, and possibly unpolished, analysis over non-peer-reviewed platforms. Nevertheless, we will communicate our findings with colleagues to guide further programs, to further optimize our use of this resource. 380819930 Assigned ID: 1201 ----- Attempting Submission 1 (Mon Apr 18 16:27:53 GMT 2016) ----- Uodated scan rate -1541802625 ----- Attempting Submission 1 (Wed Apr 20 04:30:47 GMT 2016) ----- HST Phase II Proposal 14500 (T1_DDT2_P2.apt) successfully submitted. Receipt: # 14500-1 ----- Attempting Submission 2 (Wed Apr 20 13:13:37 GMT 2016) ----- ----- Attempting Submission 3 (Wed Apr 20 19:38:31 GMT 2016) ----- We have detected three temperate Earth-sized planets transiting an ultra-cool dwarf star only 12 pc away, TRAPPIST-1. This discovery sparks the era of detailed characterization and habitability assessment of Earth-sized exoplanets. It also opens a new chapter for exoplanetology: comparative planetology in the realm of temperate terrestrial planets. TRAPPIST-1's system is currently the subject of an intense, worldwide follow-up effort that spans the electromagnetic spectrum from the UV to radio. Being uniquely suited for NIR and UV high-precision observations, HST has a key role to play in this follow-up effort. Updated ephemerids resulting from two Spitzer DDTs show that TRAPPIST-1 b and c will transit simultaneously on May 4th, 2016 at 9h10 UT providing a unique and rare opportunity to study for the first time, and simultaneously, the atmospheres of temperate Earth-sized planets outside of the Solar System. We propose a 4-orbit pre-screening program with WFC3 to definitely test the H/He-dominated atmospheric scenario for these planets and determine the relative inclination of both planets, bringing invaluable constraints on the dynamical history of the system. We propose to observe the simultaneous transits on May 4th of the two inner planets of the Ultra Cool Dwarf TRAPPIST-1 with WFC3 to determine the planetary transmission spectra. The visit will consist of four orbits timed such that that two happen before the transit, one happens during the double transit (8:47UT to 9:32UT), and one happens after the transit. Extrasolar Planets and Planet Formation 6 SUPPORTED STAR EXTRA-SOLAR PLANET EXTRA-SOLAR PLANETARY SYSTEM This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 R=16.47, I=14.02, J=11.35, K=10.30 WFC3/IR Spectroscopic No No G141 C:\Users\Julien\AppData\Local\Temp\OPVisit2624369075615249448.xml 1461180763617 53 The scheduling data was generated by CASM 24.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14500 :visit-id "01" :proposal-version -1 :trans-version "20160129" :date "20-Apr-2016 15:32:40.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 634880 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14500 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14500 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2794 :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 3180.0 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14500 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2869 :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 3180.0 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14500 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2869 :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 3180.0 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14500 :visit-id "01" :orbit-number 4 :pcs-time 222 :si-vis-utilization 2718 :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 3180.0 :pcs-gap 0 ) true 4 0