I have relaxed the phase constraint hoping this will make the program easier to schedule. 399076876 ----- Attempting Submission 1 (Fri Mar 17 11:28:01 GMT 2017) ----- ----- Attempting Submission 2 (Thu Jun 22 09:07:41 GMT 2017) ----- ----- Attempting Submission 3 (Fri Jun 23 09:52:02 GMT 2017) ----- The transition between rocky and volatile/gas-rich planets is one of the main open questions in exoplanetary research. Population studies show that this transition is not smooth, but rocky super-Earths and gas-rich mini-Neptunes with masses within 7-15 Earth masses should co-exist. Atmospheric escape is surmised to control this transition, causing some planets to lose their atmospheres to space while others retain most of their volatiles and gas. The HD 3167 planetary system, hosting two transiting close-in planets, has been identified from K2 photometry in August 2016. Through a large collaborative effort, we recently pinned down the planetary masses, revealing a duo of super-Earths: one rocky planet (b) and one volatile/gas-rich `mini-Neptune' (planet c). Thanks to its bright host star (V=8.9), this system is poised to become a benchmark target for studies of super-Earth evolution and atmospheres. HD 3167c, in particular, is the mini-Neptune transiting the brightest host star, providing a unique opportunity to access, for the first time, the atmospheric properties of this mysterious class of low-mass, low-density exoplanets. We propose 5 HST orbits to cover one transit of planet c and measure the stellar H I Lyman-alpha emission line. We hope to detect a signature from an extended exosphere escaping the planet. This has never been observed for an exoplanet below 10 Earth masses and would prove that exoplanets in this mass regime can host hydrogen envelopes. A negative result will allow us to assess the far- and extreme-UV environment of both exoplanets, which is critical for planning optimal follow-up strategies. We will observe HD3167 throughout one visit comprised of 5 consecutive HST orbits. The observations target the transit of planet HD3167c in front of its host star. Transits of HD3167c occur every 29.85 days and last 5.15 hours. The visit has been scheduled such that the first two orbits are observed before transit, the third orbit covers transit ingress, and the fourth and fifth orbits are fully observed during transit. This configuration is essential to obtain a solid pre-transit measurement. We have set a phase constraint on the ACQ exposure such that the visit starts between 4.0 and 3.33 hours before transit ingress, and observations end before transit egress. Extrasolar Planets and Planet Formation 3 false true false false false false AVAILABLE STAR K V-IV The coordinates were taken from GAIA DR1. We have verified them against HIPPARCOS coordinates, finding excellent agreement (differences < 0.002 arcsec). J2000 J2000 B = 9.77 +/- 0.02, R = 8.4 +/- 0.02, I = 8.1 +/- 0.02, J = 7.548 +/- 0.03, H = 7.203 +/- 0.04, K = 7.066 +/- 0.02 STIS/FUV-MAMA Spectroscopic No No G140M 1222 /tmp/OPVisit6017780738439581412.xml 1498211358290 The scheduling data was generated by CASM 25.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14921 :visit-id "01" :proposal-version -1 :trans-version "20170109" :date "23-Jun-2017 11:49:16.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 1340384 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14921 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14921 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2659 :al-overhead-at-end 0 :internal-dur-at-end 377 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14921 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2770 :al-overhead-at-end 0 :internal-dur-at-end 377 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14921 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2770 :al-overhead-at-end 0 :internal-dur-at-end 377 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14921 :visit-id "01" :orbit-number 4 :pcs-time 222 :si-vis-utilization 2770 :al-overhead-at-end 0 :internal-dur-at-end 377 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14921 :visit-id "01" :orbit-number 5 :pcs-time 222 :si-vis-utilization 2770 :al-overhead-at-end 0 :internal-dur-at-end 639 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2992 :pcs-gap 0 ) true 5 0