0 Assigned ID: 2663 ----- Attempting Submission 1 (Sat Jan 29 12:21:11 GMT 2022) ----- Widened starting phase constraints to 15 minutes vs 5 minutes previously. Updated zero phases of orbits 1 and 3 to consider both odd and even eclipses of the aliased period. 2105849331 ----- Attempting Submission 1 (Tue Mar 29 19:31:02 GMT 2022) ----- HST Phase II Proposal 16915 successfully submitted. Receipt: # 16915-1 ----- Attempting Submission 2 (Tue Apr 26 19:32:48 GMT 2022) ----- HST Phase II Proposal 16915 successfully submitted. Receipt: # 16915-2 ----- Attempting Submission 3 (Mon May 16 15:26:23 GMT 2022) ----- HST Phase II Proposal 16915 successfully submitted. Receipt: # 16915-3 ----- Attempting Submission 4 (Tue May 17 13:38:46 GMT 2022) ----- Our current understanding of the evolution of exoplanet atmospheres predicts the existence of a so-called 'hot-Neptune desert' - a dearth of Neptune-mass planets with orbital periods less than four days, and this prediction has so far been borne-out by observations. The discovery of LTT 9779b, a roughly two Neptune-mass planet with an orbital period of less than a day, thus provides a challenge to the current atmosphere evolution paradigm. LTT 9779b is currently the only known ultra-hot-Neptune, and Spitzer/IRAC observations find tentative evidence for an atmosphere with observable molecular signatures. Although we expect the atmospheres of hot planets to be dark at UV/optical wavelengths, TESS and CHEOPS measurements show evidence of a significant amount of light scattering from the atmosphere of LTT 9779b - likely indicating the presence of clouds. We here propose to leverage the unique capabilities of the WFC3 instrument's UVIS channel to conduct a spectroscopic study of scattered light from the atmosphere of LTT 9779b during its eclipse. Such observations will allow us to constrain the planet's energy budget, as well as robustly discern the presence of, and quantify the composition of clouds in its atmosphere. This program will be highly complementary to the planned JWST/NIRISS observations, and facilitate a deeper understanding of one of the most unique worlds discovered to date. We propose to measure the energy budget and constrain the presence and composition of clouds in the atmosphere of LTT 9779b, the only known member of the hot-Neptune desert to have retained a substantial gaseous envelope, via observations of scattered light during its eclipse. Due to its extreme levels of irradiation, LTT 9779b is the best sub-Saturn planet for such a study, and we have shown in the previous section that multiple lines of evidence indicate the presence of clouds in its atmosphere. The UVIS channel of HST/WFC3 is the best instrument to carry out these observations. These science goals require observations in the blue-optical and near UV, where the planet's thermal contribution is negligible, and the scattered signature of cloud condensates can be observed. Such observations will be impossible with the JWST, which only can observe down to 0.6 microns. Wakeford et al. (2020) demonstrated that for targets fainter than V = 7 the G280 grism yields reduced systematics, as well as higher resolution, precision and wavelength coverage than either STIS gratings (the V magnitude of LTT 9779 is 9.79). Our program also requires a sensitivity and stability that is currently beyond the reach of ground-based instruments operating in a similar wavelength range, and the critical NUV wavelength regime which enables the distinguishing between various cloud models is highly attenuated by the Earth's atmospher. Thus, ground based observations, even if they could reach a comparable sensitivity to the HST, would not be of the same scientific value as our proposed program. We include three eclipses in our program, requiring a total of 12 orbits, to ensure that we reach the required sensitivity to provide, at minimum, the most robust upper limit of geometric albedo for an ultra-hot sub-Saturn planet. Using a publicly available tool (Wakeford et al., 2020), we simulated the precision that would be obtained with the G280 grism with three eclipses, as well as the corresponding achievable photometric precision if the spectrum were to be completely binned down. This tool has shown to accurately replicate the precision achieved by the observations of Wakeford et al. (2020). We find a photometric precision of 11 ppm when stacking all three eclipses. This is sufficient to detect the scattered light eclipse of LTT 9779 b at 3sigma if its geometric albedo is at least 0.2. Given that the existing TESS and CHEOPS observations indicate a significant scattered light signal, we predict a geometric albedo for LTT 9779 b of 0.4. We also note that unlike with the IR channel of WFC3, the first orbit of the UVIS channel can be fully used (Wakeford et al., 2020). Michael Radica is a PhD candaidate experienced with exoplanet atmosphere observations at both low- and high-resolution. He will lead the reduction and analysis of this program. He is part of the NEAT JWST/NIRISS GTO program and will be in charge of the reduction and analysis of the LTT 9779 b eclipse observtaions. He is also the PI of a program underway with Gemini-S/IGRINS to observe an eclipse of LTT 9779 b in the NIR at high spectral resolution to constrain the composition of its atmosphere, and explore the interplay between observations at high- and mid/low-resolution. Jake Taylor is a post-doc specializing in modeling of cloudy exoplanet atmospheres and scattering spectra. He will aid in the analysis and interpretation of results. David Lafreniere is the PI of NEAT, a 200-h JWST GTO program (#1210) of exoplanet atmospheres characterization using transit and emission spectroscopy. Will be involved in the analysis of the planned LTT 9779 b JWST observations, which are complementary to this proposal. He will provide expertise in data reduction and precision light curve analysis. Hannah Wakeford is an expert in cloud modelling and the reduction of HST data. She lead the only previous study (Wakeford et al. 2021) to use the G280 grism for exoplanet atmosphere spectroscopy. She will lend instrument expertise, and aid in the reduction of the data. Vivien Parmentier is expert in atmospheric dynamics, radiative transfer and cloud formation models. He will help with the interpretation of the observations. Nicolas Cowan is an expert in the energy budgets of short period exoplanets via space-based measurements of thermal phase variations and optical albedo. His group has published geometric and Bond albedo estimates for hot Jupiters using data from the Hubble, Spitzer and Kepler space telescopes. He was also involved in the LTT 9779 b Kepler and Spitzer phase curve analysis by Crossfield et al. (2020), and will aid in the interpretation of the results. James Jenkins is a member of the CHEOPS team working on the eclipse of LTT 9779 b. He is an expert in precision light curve analysis and exoplanet detection. He published the detection paper for LTT 9779 b and will aid in the data reductions. Sergio Hoyer is a member of the CHEOPS team working on the eclipse of LTT 9779 b. He will aid in the light curve analysis. Romain Allart is an expert in atmosphere escape studies at low and high resolution. He will aid in the search for the signnatures of an extended atmosphere and the interpretation of these results. Exoplanets and Exoplanet Formation 3 false false true false false true false AVAILABLE STAR G V-IV This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 WFC3/UVIS Spectroscopic No No G280 /private/var/folders/5m/mqc2t7ws7258yxnpmld_y85c0000gp/T/OPVisit263061483116874970.xml 1652794206598 The scheduling data was generated by CASM 30.1. CASM was run in Phase II mode. We have specified phase constraints of 0.1983 - 0.2005 for the start of each eclipse to ensure that the second orbit is centered on the eclipse midpoint. This assumes a mimum start time of mid eclipse - T14/2 - 96min (single HST orbit) - 5min (using a 5 minute starting window). With such a start window, we should be able to capture the entire ~40min T14 in the 47min observing window, with one orbit for baseline both before and after. Since the period of this planet is <1d, we have doubled the period to 1.584d and halved the resulting phases to overcome the limitations of the APT when handling short periods. We note that the propogated error on our ephemeris (Crossfield+ 2020) is ~2mins. We have placed orient constraints to avoid contamination of the spectral trace by two nearby stars. A bias frame will be taken at the end of each visit as we have specified a custom subarray for which the appropriate calibrations will not be already available. (Tic-Visit :proposal-id 16915 :visit-id "01" :proposal-version -1 :trans-version "20211222" :date "17-May-2022 09:30:04.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1554064 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16915 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16915 :visit-id "01" :orbit-number 1 :pcs-time 383 :si-vis-utilization 2705 :al-overhead-at-end 67 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16915 :visit-id "01" :orbit-number 2 :pcs-time 392 :si-vis-utilization 2747 :al-overhead-at-end 67 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16915 :visit-id "01" :orbit-number 3 :pcs-time 392 :si-vis-utilization 2747 :al-overhead-at-end 67 :internal-dur-at-end 996 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) true 3 0 FLASH=18 added to reach the 20e- nominal background count. 3s exposure in the F300X filter reaches S/N=427 which is sufficient. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. Bias frames with same setup and subarray size as science observations are required since we have used a custom subarray. 1652794211583 The scheduling data was generated by CASM 30.1. CASM was run in Phase II mode. /private/var/folders/5m/mqc2t7ws7258yxnpmld_y85c0000gp/T/OPVisit11624738127482373238.xml We have specified phase constraints of 0.1983 - 0.2005 for the start of each eclipse to ensure that the second orbit is centered on the eclipse midpoint. This assumes a mimum start time of mid eclipse - T14/2 - 96min (single HST orbit) - 5min (using a 5 minute starting window). With such a start window, we should be able to capture the entire ~40min T14 in the 47min observing window, with one orbit for baseline both before and after. Since the period of this planet is <1d, we have doubled the period to 1.584d and halved the resulting phases to overcome the limitations of the APT when handling short periods. We note that the propogated error on our ephemeris (Crossfield+ 2020) is ~2mins. We have placed orient constraints to avoid contamination of the spectral trace by two nearby stars. A bias frame will be taken at the end of each visit as we have specified a custom subarray for which the appropriate calibrations will not be already available. (Tic-Visit :proposal-id 16915 :visit-id "02" :proposal-version -1 :trans-version "20211222" :date "17-May-2022 09:30:10.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1554064 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16915 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16915 :visit-id "02" :orbit-number 1 :pcs-time 383 :si-vis-utilization 2705 :al-overhead-at-end 67 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16915 :visit-id "02" :orbit-number 2 :pcs-time 392 :si-vis-utilization 2747 :al-overhead-at-end 67 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16915 :visit-id "02" :orbit-number 3 :pcs-time 392 :si-vis-utilization 2747 :al-overhead-at-end 67 :internal-dur-at-end 996 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) true 3 0 FLASH=18 added to reach the 20e- nominal background count. 3s exposure in the F300X filter reaches S/N=427 which is sufficient. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. Bias frames with same setup and subarray size as science observations are required since we have used a custom subarray. 1652794216414 The scheduling data was generated by CASM 30.1. CASM was run in Phase II mode. /private/var/folders/5m/mqc2t7ws7258yxnpmld_y85c0000gp/T/OPVisit6814755435120457264.xml We have specified phase constraints of 0.1983 - 0.2005 for the start of each eclipse to ensure that the second orbit is centered on the eclipse midpoint. This assumes a mimum start time of mid eclipse - T14/2 - 96min (single HST orbit) - 5min (using a 5 minute starting window). With such a start window, we should be able to capture the entire ~40min T14 in the 47min observing window, with one orbit for baseline both before and after. Since the period of this planet is <1d, we have doubled the period to 1.584d and halved the resulting phases to overcome the limitations of the APT when handling short periods. We note that the propogated error on our ephemeris (Crossfield+ 2020) is ~2mins. We have placed orient constraints to avoid contamination of the spectral trace by two nearby stars. A bias frame will be taken at the end of each visit as we have specified a custom subarray for which the appropriate calibrations will not be already available. (Tic-Visit :proposal-id 16915 :visit-id "03" :proposal-version -1 :trans-version "20211222" :date "17-May-2022 09:30:15.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1554064 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16915 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16915 :visit-id "03" :orbit-number 1 :pcs-time 383 :si-vis-utilization 2705 :al-overhead-at-end 67 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16915 :visit-id "03" :orbit-number 2 :pcs-time 392 :si-vis-utilization 2747 :al-overhead-at-end 67 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16915 :visit-id "03" :orbit-number 3 :pcs-time 392 :si-vis-utilization 2747 :al-overhead-at-end 67 :internal-dur-at-end 996 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) true 3 0 FLASH=18 added to reach the 20e- nominal background count. 3s exposure in the F300X filter reaches S/N=427 which is sufficient. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. Bias frames with same setup and subarray size as science observations are required since we have used a custom subarray. 1652794221483 The scheduling data was generated by CASM 30.1. CASM was run in Phase II mode. /private/var/folders/5m/mqc2t7ws7258yxnpmld_y85c0000gp/T/OPVisit6303563307278732140.xml We have specified phase constraints of 0.1983 - 0.2005 for the start of each eclipse to ensure that the second orbit is centered on the eclipse midpoint. This assumes a mimum start time of mid eclipse - T14/2 - 96min (single HST orbit) - 5min (using a 5 minute starting window). With such a start window, we should be able to capture the entire ~40min T14 in the 47min observing window, with one orbit for baseline both before and after. Since the period of this planet is <1d, we have doubled the period to 1.584d and halved the resulting phases to overcome the limitations of the APT when handling short periods. We note that the propogated error on our ephemeris (Crossfield+ 2020) is ~2mins. We have placed orient constraints to avoid contamination of the spectral trace by two nearby stars. A bias frame will be taken at the end of each visit as we have specified a custom subarray for which the appropriate calibrations will not be already available. (Tic-Visit :proposal-id 16915 :visit-id "04" :proposal-version -1 :trans-version "20211222" :date "17-May-2022 09:30:20.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1554064 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16915 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16915 :visit-id "04" :orbit-number 1 :pcs-time 383 :si-vis-utilization 2705 :al-overhead-at-end 67 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16915 :visit-id "04" :orbit-number 2 :pcs-time 392 :si-vis-utilization 2747 :al-overhead-at-end 67 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16915 :visit-id "04" :orbit-number 3 :pcs-time 392 :si-vis-utilization 2747 :al-overhead-at-end 67 :internal-dur-at-end 996 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) true 3 0 FLASH=18 added to reach the 20e- nominal background count. 3s exposure in the F300X filter reaches S/N=427 which is sufficient. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. FLASH=14 added, which when combined with the natural background of about 6 e- per exposure will result in 20 e- and better CTE. To limit data volume, and hence buffer dumps, we have specified SIZEAXIS2=650 and SIZEAXIS1=2250. The target trace will occupy only a narrow range in y, so this is fine. CENTERAXIS1 & CENTERAXIS2 parameters have also been specified to center the target on chip 2. A POSTARG in the y-directon of -50 arcsec has been added to further center the target on chip 2. Bias frames with same setup and subarray size as science observations are required since we have used a custom subarray.