0 Assigned ID: 1231 ----- Attempting Submission 1 (Wed Sep 30 18:52:00 GMT 2020) ----- HST Phase I Proposal 1231 successfully submitted. Receipt: # 1231-1 ----- Attempting Submission 2 (Wed Sep 30 20:57:46 GMT 2020) ----- HST Phase I Proposal 1231 successfully submitted. Receipt: # 1231-2 0 ----- Attempting Submission 1 (Mon Nov 30 17:42:57 GMT 2020) ----- Measuring the Rock-to-Ice Ratio in an Exoplanet With atmospheres hotter than 2000 K, ultra-hot Jupiters provide the unique opportunity to measure both refractory atomic metals and volatile molecules like H2O in their cloud-free transmission spectrum. The recently observed UV-optical (0.2-0.8 micron) transmission spectrum of ultra-hot Jupiter WASP-178b indicates strong absorption at short-wavelengths by atomic metals, consistent with refractory abundances between 1 and 4 times solar. Here, we propose to complete WASP-178b's UV-IR transit spectrum (0.2-1.7 micron) with WFC3/IR/G102 and G141, enabling the measurement of volatile abundances through H2O. With a measurement of refractory abundances at short wavelength and volatile abundances in the IR, we can determine the planet's rock-to-ice ratio, providing insight into WASP-178b's formation and migration history. With the addition of WASP-178b's IR spectrum, we can better compare the planet to the broader ultra-hot Jupiter population, including whether the planet has TiO and VO in its atmosphere. Our WFC3/G102 and G141 observations will provide a transmission spectrum for the transiting exoplanet WASP-178b across the 0.8-1.7 micron wavelength range. We are targeting the absorption signatures of water and metal oxides. **Observing strategy: To construct the transmission spectrum, we require two transits of WASP-178b to be observed, with WFC3 G102 and G141. The observations will be made in slitless spectroscopic mode. Our observing setup is very similar to that used in many previous successful exoplanet transit programs, such as Program 14916 (PI Spake). At the start of the HST visit, a standard phase-constrained acquisition image will be taken. The subsequent observing strategy consists of taking repeated exposures for the duration of the transit, plus time before and after the transit to establish the out-of-transit baseline flux. We will use the round-trip spatial scanning mode with a scan rate of 0.0607766 and 0.759707 arcsec/sec for the G102 and G141 visit, respectively. We will use SPARS25 and NSAMP=7. These parameters were determined using the STScI-sponsored Exo-CTK/PandExo. We will read out a subarray size of 256 pixels to reduce overheads. Individual exposure times will be 134.354 sec, resulting in a scan across 8.2 and 10.2 arcsec per exposure for G102 and G141, respectively, leaving plenty of room on the detector to estimate the background flux. Each transit of WASP-178b lasts 208 minutes. We therefore require 5 consecutive HST orbits. The first orbit serves to allow the telescope to thermally relax into its new pointing position, which is a standard procedure adopted by all HST transiting exoplanet observations. The remaining orbits will provide good phase coverage during transit, and allow for sufficient time (2 HST orbits - one before transit, one after transit) to establish the baseline stellar flux necessary to accurately measure the transit depth. We will obtain 16 science exposures per HST orbit (8 forward, 8 reverse), coming to a total of 32 in-transit and 32 out-of-transit exposures. **Signal-to-noise estimates: WASP-178b is a bright target in the conventional sense (J=9.775mag). The challenge with exoplanet transmission spectroscopy is to measure subtle changes in the system brightness across different wavelength channels, via variations in the transit depth. We used the HST Exposure Time Calculator with the observational setup described above to calculate a SNR of ~2000 per resolution element per exposure. Note that this flux will be spread over 70-80 pixel columns due to the spatial scan (see above), so there is no risk of saturation. Dr. Lothringer is an expert in both observing exoplanet atmospheres with HST and the modeling of atmospheres with PHOENIX. He has extensive experience studying the highly irradiated class of ultra-hot Jupiters. Dr. Lothringer is PI of HST programs 16086, 16142, and 16270 and is co-I on 6 other programs. Prof. Sing is an expert in the analysis and interpretation of HST datasets with HST. Prof. Sing is also an expert in calculating atmosphere models to interpret HST observations, particularly with the ATMO code. Prof. Sing has been PI of several HST programs, including small, large, and Treasury programs. Dr. Hannah Wakeford is an expert in the analysis and interpretation of HST datasets, particularly with HST/WFC3. She has been a PI or co-I on 20 different HST programs Dr. Nikolay Nikolov is an expert in analyzing HST exoplanet observations with extensive experience with HST/STIS and HST/WFC3. He has been a PI or co-I on over a dozen HST programs. He is an STScI HST/WFC3 instrument scientist. Dr. Kevin Stevenson is an expert in the analysis and observational setup of exoplanet observations with HST. He has worked as an STScI HST/WFC3 instrument scientist. He has been a PI or co-I on over two dozen HST programs. Mr. Rustamkulov has experience in both modeling exoplanet transit spectra and observing with ground and space-based assets. He currently leading the reduction of data from HST Programs 16039 and 16270. Exoplanets and Exoplanet Formation 6 false false false false false false false SUPPORTED STAR A0-A3 V-IV EXTRA-SOLAR PLANETARY SYSTEM NO This object was generated by the targetselector and retrieved from the SIMBAD database. Lothringer added parallax, magnitudem uncertainty, and alternate names. WASP-178 KELT-26 J2000 J2000 WFC3/IR Spectroscopic No No G102 WFC3/IR Spectroscopic No No G141 The scheduling data was generated by CASM 28.2. CASM was run in Phase II mode. WFC3/G141 5-orbit transit time series visit. It is essential that the five HST orbits be scheduled in a contiguous block, free of the SAA. We have defined each HST orbit within a non-interruptible sequence, to ensure that all exposures defined within the sequence are taken during the same HST orbit. We will use round-trip spatial scanning mode to increase observing efficiency. Y= -7" offset has been applied such that the target spatial scan is near the middle of the 256 subarray. Nearby stars are relatively dim (J>15), but we will work with the scheduling and instrument teams to optimize any roll constraints if they are determined to be necessary. 1613728926000 288.73603552688553 (Tic-Visit :proposal-id 16450 :visit-id "01" :proposal-version -1 :trans-version "20200619" :date "19-Feb-2021 16:32:34.0" :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 752496 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16450 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16450 :visit-id "01" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2496 :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 3238 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16450 :visit-id "01" :orbit-number 2 :pcs-time 392 :si-vis-utilization 2784 :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 3238 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16450 :visit-id "01" :orbit-number 3 :pcs-time 392 :si-vis-utilization 2784 :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 3238 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16450 :visit-id "01" :orbit-number 4 :pcs-time 392 :si-vis-utilization 2784 :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 3238 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16450 :visit-id "01" :orbit-number 5 :pcs-time 392 :si-vis-utilization 2784 :al-overhead-at-end 0 :internal-dur-at-end 386 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3238 :pcs-gap 0 ) false 5 0 Direct image to assist with wavelength calibration. Saturated, but the image is only used to find the reference detctor possition. /private/var/folders/0b/qbp4bysx6vdbfxvp_xw3dyxw00023y/T/OPVisit1313292702492745779.xml The scheduling data was generated by CASM 29.0. CASM was run in Phase II mode. WFC3/G102 5-orbit transit time series visit. It is essential that the five HST orbits be scheduled in a contiguous block, free of the SAA. We have defined each HST orbit within a non-interruptible sequence, to ensure that all exposures defined within the sequence are taken during the same HST orbit. We will use round-trip spatial scanning mode to increase observing efficiency. Y= -7" offset has been applied such that the target spatial scan is near the middle of the 256 subarray. Nearby stars are relatively dim (J>15), but we will work with the scheduling and instrument teams to optimize any roll constraints if they are determined to be necessary. (Tic-Visit :proposal-id 16450 :visit-id "02" :proposal-version -1 :trans-version "20200619" :date "22-Feb-2021 14:40:59.0" :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 675680 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16450 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16450 :visit-id "02" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2496 :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 3238 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16450 :visit-id "02" :orbit-number 2 :pcs-time 392 :si-vis-utilization 2436 :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 3238 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16450 :visit-id "02" :orbit-number 3 :pcs-time 392 :si-vis-utilization 2436 :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 3238 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16450 :visit-id "02" :orbit-number 4 :pcs-time 392 :si-vis-utilization 2436 :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 3238 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16450 :visit-id "02" :orbit-number 5 :pcs-time 392 :si-vis-utilization 2436 :al-overhead-at-end 0 :internal-dur-at-end 407 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3238 :pcs-gap 0 ) true 5 0 Direct image to assist with wavelength calibration. Saturated, but the image is only used to find the reference detctor possition.