0 Assigned ID: 424 ----- Attempting Submission 1 (Fri Apr 10 10:47:16 GMT 2015) ----- HST Phase I Proposal 424 (Hat-26.pages.prop.pdf.apt) successfully submitted. Receipt: # 424-1 ----- Attempting Submission 2 (Fri Apr 10 15:16:32 GMT 2015) ----- HST Phase I Proposal 424 (Hat-26.pages.prop.pdf.apt) successfully submitted. Receipt: # 424-2 Loosened phase constraints for visit 2, and updated the ephemeris. ============================== Switched to G102 Expsoure time and scan rate adjusted ============================== Changed to Available Mode. Added the following to the Observing Desription --------- Additional Comments ---------- STIS visits use the G750L with Wavecal=No, as in our previous similar programs such as GO 12473 and GO 11740, such that the duty cycle and photometric precision is maximised and the thermal breathing trends can be efficiently removed, which is only possible with an uninterrupted photometric time-series. Also as in GO 12473, the other STIS settings are set to maximize counts and reduce readout time overheads. CR-SPLIT=NO, Gain=4, Sizeaxis2=128. ------------------------- Aug 13. Changed visit 1 to SCHED 50 and reduced the exposure times to 267 seconds. -1711961748 ----- Attempting Submission 1 (Tue Jul 21 13:36:06 GMT 2015) ----- HST Phase II Proposal 14110 (GO14110_HAT-P-26.apt) successfully submitted. Receipt: # 14110-1 ----- Attempting Submission 2 (Wed Jul 22 14:58:56 GMT 2015) ----- ----- Attempting Submission 3 (Thu Aug 13 12:00:37 GMT 2015) ----- ----- Attempting Submission 4 (Mon Feb 01 13:45:25 GMT 2016) ----- ----- Attempting Submission 5 (Tue Apr 26 10:21:22 GMT 2016) ----- Using transits to obtain transmission spectra is a powerful technique to enable detailed studies of exoplanet atmospheres. The Neptune-mass exoplanet HAT-P-26b is one of a small handful of low-mass planets currently accessible to atmospheric measurements. As a large-radius Neptune-mass planet, the planet's low bulk density indicates it must have a substantial atmosphere, with a high hydrogen fraction likely. The atmosphere could have arisen from many different sources resulting in a wide range of possibilities, including ones dominated by hydrogen or heavier species such as water. As the measured mass and radius of a planet do not uniquely specify the atmospheric composition, transmission spectroscopy is the only way to further characterize its chemical makeup. The HST observations proposed here will carry out these vital initial atmospheric observations, with a broad wavelength range covering optical to near-IR sensitive to the expected atmospheric features of water, methane, sodium, potassium, and Rayleigh scattering. With only one in five low-mass exoplanets probed with HST currently showing spectral features, HAT-P-26b is one of the best current candidates likely to have large signals given its large predicted hydrogen fraction. With both optical and near-IR spectra, these observations will measure the atmospheric scale height and definitively determine if the exoplanet has an atmosphere with substantial hydrogen, as predicted by thermal evolution models. HAT-P-26b represents a bridge between the featureless spectra observed in a number of the smaller sub-Neptune/super-Earth exoplanets, and the large-amplitude features observed in hot Jupiters. With only one in five low-mass exoplanets probed with HST currently showing spectral features, HAT-P-26b is one of the best current candidates likely to have large signals given its large predicted hydrogen fraction. The HST observations proposed here will carry out these vital initial atmospheric observations, with a broad wavelength range covering optical to near-IR sensitive to the expected atmospheric features of water, methane, sodium, potassium, and Rayleigh scattering. Our immediate scientific objectives are to: - Characterize the Neptune-mass exoplanet HAT-P-26b by directly measuring the atmospheric scale height, distinguishing between H and metal-rich compositions - Test the hypothesis that enlarged low-mass exoplanets have H-rich atmospheres - Identify the expected molecular species of H2O and CH4 - Search for optical Rayleigh scattering signatures of hazes or clouds Our further strategic scientific aims are to: - Constrain the abundances of H2O and CH4 searching for super-solar abundances - Probe the alkali metal and CH4 chemistry in a warm Neptune-mass planet Observing Strategy We will use the STIS spectrograph to cover the optical range sensitive to Rayleigh scattering and the alkali metals Na and K, as well as the WFC3 for near-IR coverage which is strongly sensitive to water and methane features. We will repeat our successful observing strategies in which we have now perfected very high S/N optical and near-IR transiting observations with HST (PI Sing: GO-12473, GO-11572, GO-11117; e.g. Sing et al. 2015, Wakeford et al. 2013). We propose to observe HAT-P-26b with both the STIS/G750L and WFC3/G141 during one transit each, each visit consisting of five consecutive orbits (10 total). The spirit of transit observations is to attempt to gather as many spectra as possible before, during, and after a transit event, with each image as identical as possible. As a transit observation consists of measuring a drop in stellar flux during the event, identical exposures are resistant to uncertainties in flat-fielding and very high photometric precisions are possible. The first orbit is expected to have systematically low flux, as consistently observed in previous STIS and WFC3 programs. This is due to telescope thermal relaxation, will likely not be utilized in our study, and is not included in our S/N calculations. This is a well-known phenomenon, and all other similar transiting HST programs over the past 14 years have adopted this strategy, which circumvents the un-correctable systematic errors in the first orbit. During a visit, two orbits will be used to determine the baseline flux, one before and one after transit, while two occur during the transit event. Signal-To-Noise STIS: We will use the STIS and G750L gratings to cover the wavelength range from 5500-10200 Ang and use the 52'x2' slit to minimize slit losses. As we have done for GO-12473, we will adopt exposure times close to 279 seconds, with a sub-array size of 128 for faster readout, which will give high S/N per image as well as sufficient time sampling of the HST orbital-phase trend such that it can be modeled and removed successfully. There will not be any gaps for buffer dumps. We used the ETC to calculate the count-rate and S/N levels for HAT-P-26b with the STIS G750L grating. While the ETC error budget is dominated by photon-noise, this error estimation is realistic, as the STIS instrument has repeatedly demonstrated the ability to produce near-Poisson limited high S/N photometric light-curves (see Sing et al. 2011, 2013, 2015). For each orbit, we will take 10 exposures of 279 seconds each, with 20 second overheads. For each exposure, S/N levels per resolution element of 400 at 7500 Ang are reached for the G750L. WFC3: The visit using the WFC3/G141 will use the same observational strategy as our program GO-12473, which uses spacial scanning mode to dramatically increase observational overheads and obtain vastly higher S/N levels. During spacial scan mode, the telescope is slowly slewed in the cross-dispersion direction while the camera is exposing. The spectra become spread out over a large pixel area of the detector, providing very high S/N levels and vastly improved duty cycles. We will use exposure times close to 90 seconds, which give S/N levels between 1,414 to 1,233 per resolution element between 1.15 to 1.65 um. With overheads and using subarray readouts, 27 exposures can be taken during each orbit. WFC3: The visit using the WFC3/G141 will use the same observational strategy as our program GO-12473, which uses spacial scanning mode to dramatically increase observational overheads and obtain vastly higher S/N levels. During spacial scan mode, the telescope is slowly slewed in the cross-dispersion direction while the camera is exposing. The spectra become spread out over a large pixel area of the detector, providing very high S/N levels and vastly improved duty cycles. We will use exposure times close to 90 seconds, which give S/N levels between 1,414 to 1,233 per resolution element between 1.15 to 1.65 um. With overheads and using subarray readouts, 27 exposures can be taken during each orbit. --------- Additional Comments ---------- STIS visits use the G750L with Wavecal=No, as in our previous similar programs such as GO 12473 and GO 11740, such that the duty cycle and photometric precision is maximised and the thermal breathing trends can be efficiently removed, which is only possible with an uninterrupted photometric time-series. Also as in GO 12473, the other STIS settings are set to maximize counts and reduce readout time overheads. CR-SPLIT=NO, Gain=4, Sizeaxis2=128. EXTRA-SOLAR PLANETS 12 false false false false false false AVAILABLE STAR EXTRA-SOLAR PLANETARY SYSTEM K V-IV NO This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 STIS/CCD Spectroscopic No No G750L 7751 WFC3/IR Spectroscopic No No G141 The scheduling data was generated by CASM 24.0. CASM was run in Phase II mode. 1461666033830 /private/var/folders/fr/68vxssq52d7g3p5sbf4q8h9r0003rb/T/OPVisit1183100038636732059.xml HAT-P-26. G750L. STIS visit. It is essential that the five orbits be scheduled in a coninuous block, free of the SAA. 1453745630000 288.7620952091814 (Tic-Visit :proposal-id 14110 :visit-id "01" :proposal-version -1 :trans-version "20160129" :date "26-Apr-2016 11:20:32.0" :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 185152 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14110 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14110 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2725 :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 3140 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14110 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2908 :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 3140 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14110 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2908 :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 3140 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14110 :visit-id "01" :orbit-number 4 :pcs-time 222 :si-vis-utilization 2908 :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 3140 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14110 :visit-id "01" :orbit-number 5 :pcs-time 222 :si-vis-utilization 2908 :al-overhead-at-end 120 :internal-dur-at-end 1820 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3140 :pcs-gap 0 ) true 5 0 Short exposure to minimize instrument systematic of first exposure in each orbit. Short exposure to minimize instrument systematic of first exposure in each orbit. Short exposure to minimize instrument systematic of first exposure in each orbit. Short exposure to minimize instrument systematic of first exposure in each orbit. Short exposure to minimize instrument systematic of first exposure in each orbit. Explicit WAVECAL, auto-waves disabled to increase duty cycle Expected peak count level = 50,000 e- The scheduling data was generated by CASM 24.0. CASM was run in Phase II mode. 1461666061066 /private/var/folders/fr/68vxssq52d7g3p5sbf4q8h9r0003rb/T/OPVisit4419265037269572425.xml WFC3 IR transit of HAT-P-26. It is essential that the five orbits be scheduled in a coninuous block, free of the SAA. We will use the spacial scanning mode to lengthen the spectrum along the slit during the exposures, to avoid saturation on relatively long exposures. This mode greatly increases the efficiency. (Tic-Visit :proposal-id 14110 :visit-id "02" :proposal-version -1 :trans-version "20160129" :date "26-Apr-2016 11:20:58.0" :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 1718800 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14110 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14110 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2875 :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 14110 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2981 :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 14110 :visit-id "02" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2981 :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 14110 :visit-id "02" :orbit-number 4 :pcs-time 222 :si-vis-utilization 2981 :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 14110 :visit-id "02" :orbit-number 5 :pcs-time 222 :si-vis-utilization 2981 :al-overhead-at-end 0 :internal-dur-at-end 436 :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 wavelegnth calibration. Phase constrained so transit occurs between 2nd and 3rd contact.