0 Assigned ID: 1125 ----- Attempting Submission 1 (Fri Apr 11 23:57:22 GMT 2014) ----- HST Phase I Proposal 1125 (he2cycle22.apt) successfully submitted. ----- Attempting Submission 2 (Fri Apr 11 23:59:32 GMT 2014) ----- HST Phase I Proposal 1125 (he2cycle22.apt) successfully submitted. The proposal description highlights some preferences for this program: 1. COS LP3 is strongly preferred over LP2. 2. Visits of the same target should be scheduled with minimal time gap. 3. We would prefer our observations to be taken soon after the move to LP3. -2112515390 ----- Attempting Submission 1 (Wed Jul 23 08:03:25 GMT 2014) ----- The advent of GALEX and COS have revolutionized studies of HeII reionization. Observations of the FUV-brightest QSOs have resulted in a order-of-magnitude increase in science-grade HeII Lya absorption spectra in the HST archive. The clear picture emerging is that COS has successfully pinpointed the end of HeII reionization at z~2.7. Based on this, and our team's state-of-the-art radiative transfer simulations, one expects complete Gunn-Peterson absorption at higher redshifts. However, surprisingly, our analysis of the three existing sightlines at z>3.5 reveals high-transmission regions consistent with expectations for a reionized IGM, in striking conflict with the models. Explaining these measurements may require invoking other exotic sources of hard photons at high-z, which would amount to a paradigm shift in our understanding of HeII reionization, with concomitant implications for HI reionization. The unequivocal path forward is COS spectra of more QSOs at z>3.5, deep into the reionization era, to put this tentative result on firm statistical footing. We request 24 orbits to obtain science-grade COS far-UV spectra of the 3 brightest HeII QSOs at z>3.5, which will double the HeII pathlength at high-z and test tantalizing indications that HeII reionization began at z>4 and lasted over 1 Gyr. These spectra are complemented by ancillary data from 8m telescopes, including echelle spectra of the coeval HI Lya forest, and our dedicated survey for QSOs in the foreground of each HeII sightline. Our targets are the only viable sources probing z>3.5 in a reasonable orbit request, and it is critical to HST's legacy to solve this riddle before the mission ends. We will obtain COS FUV G140L spectra of 3 z~3.8 quasars to characterize intergalactic HeII Lyman alpha absorption along their sightlines. Two targets have been confirmed as HeII-transparent in previous cycles, but lack science-grade HST/COS follow-up spectroscopy. Our third target is the 2nd UV-brightest quasar at z>3.5, discovered by our team in a dedicated survey. Our targets have accurate magnitudes covering the quasar continuum just redward of the HeII break (GALEX FUV, HST/ACS F150LP), and sufficiently accurate GALEX NUV magnitudes for reliable acquisition via ACQ/IMAGE. All targets are safe to observe with COS and have precise coordinates from SDSS or Pan-STARRS. Our targets are quite faint in the NUV, resulting in long NUV acquisition exposure times of 150-900sec. For the faintest target (SDSSJ1137+6237, NUV=24.0) we limit the acquisition exposure time to 900sec yielding S/N=30 instead of the recommended S/N=40, in order to limit the impact of dark current on the target centering. In accordance with our Phase I proposal we request CVZ observations for SDSSJ1137+6237. The G140L grating provides the wavelength coverage to define the quasar continuum and the necessary resolution to measure the onset of patchy HeII absorption. We require a S/N~3 per resolution element at 1500A, which results in a total request of 24 orbits for our three targets. Continuous wavelength coverage at good sensitivity (lambda>1150A) is required to maximize the coverage of the HeII Lyman alpha absorption, only provided by the G140L 1105A setup. We will use all FP-POS offsets in consecutive orbits of a visit. Spectra will be recorded in TIME-TAG mode with concurrent wavelength calibration (TAGFLASH). Time intervals spent in the Earth's shadow will be used to correct for geocoronal OI and NI emission. Given our faint sources, airglow will dominate the COS count rates. However, even at the high airglow conditions conservatively assumed in our ETC calculations, buffer times are longer than the exposure times, except for the CVZ target. All exposure times have been adjusted to use the full visibility period in each orbit. For the CVZ target the buffer time has been adjusted to maximize the exposure time according to Section 5.4.2 of the COS Instrument Handbook. Due to the time-dependent sensitivity of COS and COS detector gain sag, we request that visits of the same target (SDSSJ1137+6237: Visit 1 and 2; SDSSJ1614+4859: Visit 3 and 4) are scheduled within 60 days of another. The time gap should be minimized, depending on the observing schedule. Coaddition of data taken in the Poisson limit of COS over several visits requires the sensitivity and detector characteristics to be at least approximately equal. This also requires that all observations of a given target are performed at the same lifetime position of COS. Gain sag limits the accuracy of the COS background subtraction, which is critical to reach our science goals. Therefore, we strongly prefer all observations to be performed at COS lifetime position 3, and preferably as soon as possible after the move, in order to minimize gain sag. QUASAR ABSORPTION LINES AND IGM Default false true false false false SUPPORTED GALAXY LYMAN ALPHA CLOUD QSO SDSSJ113721.72+623707.2 J2000 J2000 ACS F150LP=22.83+-0.10, GALEX NUV=24.10+-0.34 GALAXY LYMAN ALPHA CLOUD QSO SDSSJ161426.81+485958.8 J2000 J2000 ACS F150LP=21.83+-0.10, GALEX NUV=22.55+-0.39 GALAXY LYMAN ALPHA CLOUD QSO J2000 J2000 GALEX FUV=21.60+-0.34, NUV=21.55+-0.29 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 1404209686184 /Users/gabor/Documents/proposals/hstcycle22/OP-cache/he2cycle22_phase2-v01.xml Timing link suitability includes constraints ([Sequence (01 02) within 60.0 days]) The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13875 :visit-id "01" :proposal-version -1 :trans-version "20140605" :date "01-Jul-2014 12:14:45.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 678592 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13875 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 13875 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 27935 :al-overhead-at-end 0 :internal-dur-at-end 366 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) true 5 0 The target is faint in the NUV, but has reasonably accurate photometry available. The spectral energy distribution likely rises steeply towards the FUV, but the more accurate flux from HST/ACS F150LP might indicate that the target is somewhat brighter in the NUV than the GALEX measurement. An acquisition exposure of 900sec calibrated to NUV=24.0 yields S/N=30 (see ETC result), enough to center the source in the COS PSA. For the recommended S/N=40, one would need 1600sec (COS.ta.616389), which is doable for a CVZ target, but might cause problems in the target centering due to dark current. The ETC run uses high airglow conditions for a conservative estimate of the buffer time, given the long exposure time and the generally high background conditions in the CVZ. The buffer time has been adjusted to maximize the exposure time according to Section 5.4.2 of the COS Instrument Handbook. 1405937859841 /Users/gabor/Documents/proposals/hstcycle22/OP-cache/he2cycle22_phase2-v02.xml Timing link suitability includes constraints ([Sequence (01 02) within 60.0 days]) The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13875 :visit-id "02" :proposal-version -1 :trans-version "20140605" :date "21-Jul-2014 12:17:39.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 678592 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13875 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 13875 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 27935 :al-overhead-at-end 0 :internal-dur-at-end 366 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) true 5 0 The target is faint in the NUV, but has reasonably accurate photometry available. The spectral energy distribution likely rises steeply towards the FUV, but the more accurate flux from HST/ACS F150LP might indicate that the target is somewhat brighter in the NUV than the GALEX measurement. An acquisition exposure of 900sec calibrated to NUV=24.0 yields S/N=30 (see ETC result), enough to center the source in the COS PSA. For the recommended S/N=40, one would need 1600sec (COS.ta.616389), which is doable for a CVZ target, but might cause problems in the target centering due to dark current. The ETC run uses high airglow conditions for a conservative estimate of the buffer time, given the long exposure time and the generally high background conditions in the CVZ. The buffer time has been adjusted to maximize the exposure time according to Section 5.4.2 of the COS Instrument Handbook. /Users/gabor/Documents/proposals/hstcycle22/OP-cache/he2cycle22_phase2-v03.xml 1404209690930 Timing link suitability includes constraints ([Sequence (03 04) within 60.0 days]) The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. 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CASM was run in Phase II mode. 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CASM was run in Phase II mode. (Tic-Visit :proposal-id 13875 :visit-id "05" :proposal-version -1 :trans-version "20140605" :date "01-Jul-2014 12:14:56.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 243664 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13875 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13875 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2888 :al-overhead-at-end 0 :internal-dur-at-end 76 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3226 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13875 :visit-id "05" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3004 :al-overhead-at-end 0 :internal-dur-at-end 95 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3226 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13875 :visit-id "05" :orbit-number 3 :pcs-time 222 :si-vis-utilization 3004 :al-overhead-at-end 0 :internal-dur-at-end 95 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3226 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13875 :visit-id "05" :orbit-number 4 :pcs-time 222 :si-vis-utilization 3004 :al-overhead-at-end 0 :internal-dur-at-end 423 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3226 :pcs-gap 0 ) true 4 0 The ETC run conservatively assumes high background conditions, but given the faint target, the buffer time is still considerably longer than the exposure time.