Connecting Earth with its Galactic Environment: Probing Our Interstellar Past Along the Historical Solar Trajectory

0 Assigned ID: 345 ----- Attempting Submission 1 (Fri Apr 10 03:15:49 GMT 2015) ----- 0 ----- Attempting Submission 1 (Thu Jul 23 18:12:26 GMT 2015) ----- Connecting Earth with its Galactic Environment: Probing Our Interstellar Past Along the Historical Solar Trajectory We propose to observe a sample of stars along the historical solar trajectory to probe the physical properties of our past interstellar environments. For more than 90 years there has been speculation surrounding the relationship between the interstellar medium, its influence on our heliosphere, and ultimately on variations in the atmosphere and even organism evolution here on Earth. By looking locally, at our most recent interstellar history, we can minimize many of the complications that have made establishing such a relationship difficult. The low column densities require high resolution spectroscopy of the strongest resonance lines, which are in the UV. This program will complement a ground-based survey that utilized the two strongest transitions in the optical, CaII and NaI, but was unable detect the lowest interstellar column densities within 100 pc. Therefore, this is necessarily a UV program and the strength of UV transitions will ensure detection of this material. The observations will be used to measure the number of clouds, their distances, densities, and velocities along this special line of sight. These measurements will be used to reconstruct the recent variations in heliospheric structure and Galactic cosmic ray flux as a result of passing through these clouds. Our observational results can be compared with existing geological tracers of cosmic rays. If these observations support a relationship between our past interstellar surroundings and the cosmic ray flux at 1 AU, it would have important implications for the history of the Earth's biosphere, as well as a new context to evaluate the interstellar environments of nearby stars with planetary systems. Target Selection and Availability: In order to probe the interstellar material along the solar historical trajectory, we propose observations of 8 stars within the historical solar path, out to a distance of ~50 pc. The historical solar path is defined by measurements by Dehnen & Binney (1998), and is in the direction of l = 207.7 deg and b = -32.4 deg. The targets are selected from within an observing cone that is defined as the region in which interstellar clouds have not had sufficient time to move out of the line of sight, or to have evolved, since the Sun was at that location. Hence, the observing cone increases dramatically near the Sun. Desired Spectral Coverage: Each target will be observed at high spectral resolution using the E230H grating, which can simultaneously cover multiple FeII and MgII resonance lines with different oscillator strengths. For three targets, an additional E140M exposure is also requested to measure HI and DI absorption, in order to trace any depletion variations that may effect the FeII and MgII column density measurements. Use of FeII and MgII absorption to measure ISM properties is motivated by a number of reasons: (1) These are two of the heaviest ions observed in the LISM and therefore have intrinsically narrow lines, which improves our ability to fully resolve the velocity structure of the interstellar clouds along the line of sight. (2) Both ions are expected to be the dominant ionization stage in these clouds for a wide range of temperatures (Slavin & Frisch 2002; Lehner et al. 2003). (3) All four resonance lines are available in one E230H STIS echelle setting. By simultaneously fitting multiple absorption lines, accurate measurements of a wide range of column densities are feasible, while minimizing the systematic errors involved in continuum placement, saturation, and line blending. (4) Stellar observations in the near-UV (NUV), 2200-2800 Angstroms, are very efficient, and only require 1 orbit each. Alone, FeII and MgII absorption cannot provide the complete picture of the intervening ISM. When combined with observations of other ions, a whole host of fundamental physical measurements can be made for each cloud, including, depletions, ionization structure, temperature, and turbulent velocity. In particular, measuring the depletion of these ions onto dust grains is critical to estimating an accurate volume density. For this reason, three E140M exposures are requested to measure the interstellar HI (via DI) absorption. Various other ions, such as CII, NI, OI, SiII, SiIII, will also be observed (see Redfield & Linsky (2004a) for a full inventory LISM measurements of these ions within 100 pc). Desired Spectral Resolution: The high spectral resolution of STIS is necessary to model the ISM absorption line profiles. Only by resolving the velocity components of the ISM clouds, can one measure accurate physical properties of these clouds. Hence, we propose to use the high resolution E230H grating to observe MgII and FeII. These ``heavy'' ions are not significantly broadened thermally, and provide sharp line profiles to resolve the velocity structure of the ISM along the line of sight. Because hydrogen and deuterium are thermally broadened, we are able to model their absorption with medium resolution spectra, and therefore, to maximize S/N, we plan to use the E140M setting. Due to the wide spectral range of the E140M grating of STIS, we will obtain practically the entire far-UV band from 1150-1700 Angstroms and several ISM absorption lines (e.g., HI, DI, CII, NI, OI, SiII, SiIII). Desired Aperture Size: All of the E230H observations will be taken through the 0.2x0.09 arcsecond slit, which requires a peak-up, to ensure the target is well centered. The E140M spectra will be observed through the 0.2x0.2 slit to maximize the S/N. Stars are significantly fainter in the FUV, and since we will already have a well-calibrated high resolution E230H spectra of the same sight line, we plan to use the larger slit to increase the signal. Desired Signal-to-Noise and Exposure Times: Because cool star spectra are emission line sources in the UV, estimating expected S/N for our planned spectra requires first estimating Lyman-alpha and MgII fluxes, which we can do by extrapolating from previously observed stars. Chromospheric line fluxes (such as MgII and Lyman-alpha) are related to X-ray fluxes (Ayres et al. 1995). Wood et al. (2005) provide Lyman-alpha spectra for many stars and serve as our comparison sample. This also emphasizes the appeal of M star targets, which have high chromospheric activity levels and therefore strong emission lines with which to observe LISM absorption against. When L_X is not known, we estimate the flux from stars of similar spectral type scaled by V magnitude. For each observation the preparation time is only 26 minutes: 6 minutes for the initial guide-star acquisition, 6 minutes for the target acquisition, 6 minutes for the target acquisition peak-up, and 8 minutes for the first spectroscopic MAMA exposure overhead. This typically leaves 24 minutes, more than enough time to get a E230H spectrum with a signal-to-noise (S/N) ratio >10 at the half-maximum (that is one half the FWHM from line center, because the ISM absorption is unlikely to centered at the same velocity as the star) of the strong MgII lines. Because multiple lines of the same ion are observed together, even a modest (S/N) ratio of 10 in one line is enough to make accurate measurements of weak column densities, even in blended profiles (demonstrated in Redfield & Linsky 2002). We have selected three sight lines that are most favorable for FUV observations to acquire the Lyman-alpha line to measure HI and DI column densities. After acquisition and overheads, we expect at least 37 minutes of exposure time to be available in the second orbit for the E140M exposure, and 44 minutes in subsequent orbits. In order to accurately model the Lyman-alpha profile, we require a S/N > 35 (see Wood et al. 2005), which is achievable in all cases, in just 2 additional orbits. Brightness Limits: Most of our targets are late-type stars which have UV spectra characterized by weak continua, but strong emission lines. For this reason, these targets fall far short of the global brightness limit. The emission lines also fall far short of the local brightness limit. The two emission lines of prime interest in this proposal (Lyman-alpha and MgII) are also the brightest, and therefore, the procedure given above for estimating the S/N near their peaks is also utilized to test for brightness limit violations. None of the stars exceed brightness limits. Our brightest star, HD32147, has reliable IUE data, which provide accurate estimates of the S/N and count rates, which are more than an order of magnitude below the global and local count rates. ISM AND CIRCUMSTELLAR MATTER 12 false true false false SUPPORTED STAR M V-IV NO No target star was identified by the BOT in the observed field. DSS images clearly indicate a bright isolated target star (brightest within 100 arcsec). Clearly the target star is the dominant object in the field of view. LHS1723 J2000 J2000 TYPE=M4V, B-V=1.72, E(B-V)=0, F-LINE(2796)=0.98e-12, W-LINE(2796)=0.35, F-LINE(1215)=3.48e-12, W-LINE(1215)=0.6 STAR K V-IV NO IUE SPECTRUM: SWP16520, LWR11179 No target star was identified by the BOT in the observed field. DSS images clearly indicate a bright isolated target star (brightest within 100 arcsec). Clearly the target star is the dominant object in the field of view. GJ183 HR1614 J2000 J2000 TYPE=K3V, B-V=1.06, E(B-V)=0, F-LINE(2796)=5.64e-12, W-LINE(2796)=0.5, F-LINE(1215)=2.94e-12, W-LINE(1215)=0.65 STAR M V-IV NO No target star was identified by the BOT in the observed field. DSS images clearly indicate a bright isolated target star (brightest within 100 arcsec). Clearly the target star is the dominant object in the field of view. LHS1731 HIP23512 J2000 J2000 TYPE=M3V, B-V=1.64, E(B-V)=0, F-LINE(2796)=0.35e-12, W-LINE(2796)=0.35 STAR M V-IV NO No target star was identified by the BOT in the observed field. DSS images clearly indicate a bright isolated target star (brightest within 100 arcsec). Clearly the target star is the dominant object in the field of view. LHS203 HIP23932 J2000 J2000 TYPE=M3V, B-V=1.51, E(B-V)=0, F-LINE(2796)=0.26e-12, W-LINE(2796)=0.35 STAR M V-IV NO Target star was identified by the BOT in the observed field. DSS images clearly indicate a bright isolated target star (brightest within 100 arcsec). Clearly the target star is the dominant object in the field of view. GJ173 HIP21556 J2000 J2000 TYPE=M1V, B-V=1.51, E(B-V)=0, F-LINE(2796)=0.89e-12, W-LINE(2796)=0.35, F-LINE(1215)=2.17e-12, W-LINE(1215)=0.6 STAR M V-IV NO Target star was identified by the BOT in the observed field. DSS images clearly indicate a bright isolated target star (brightest within 100 arcsec). Clearly the target star is the dominant object in the field of view. HIP21765 J2000 J2000 TYPE=M0V, B-V=1.48, E(B-V)=0, F-LINE(2796)=0.27e-12, W-LINE(2796)=0.35 STAR K V-IV NO Target star was identified by the BOT in the observed field. DSS images clearly indicate a bright isolated target star (brightest within 100 arcsec). Clearly the target star is the dominant object in the field of view. GJ3314 HIP22288 J2000 J2000 TYPE=K5V, B-V=1.23, E(B-V)=0, F-LINE(2796)=0.30e-12, W-LINE(2796)=0.5 STAR G V-IV NO Target star was identified by the BOT in the observed field. DSS images clearly indicate a bright isolated target star (brightest within 100 arcsec). Clearly the target star is the dominant object in the field of view. HIP21963 J2000 J2000 TYPE=G5V, B-V=0.63, E(B-V)=0, F-LINE(2796)=0.88e-12, W-LINE(2796)=0.6 STIS/NUV-MAMA Spectroscopic No No E230H 2713 STIS/FUV-MAMA Spectroscopic No No E140M 1425 STIS/NUV-MAMA Spectroscopic No No E230H 2713 STIS/FUV-MAMA Spectroscopic No No E140M 1425 STIS/NUV-MAMA Spectroscopic No No E230H 2713 STIS/NUV-MAMA Spectroscopic No No E230H 2713 STIS/NUV-MAMA Spectroscopic No No E230H 2713 STIS/FUV-MAMA Spectroscopic No No E140M 1425 STIS/NUV-MAMA Spectroscopic No No E230H 2713 STIS/NUV-MAMA Spectroscopic No No E230H 2713 STIS/NUV-MAMA Spectroscopic No No E230H 2713 1437591375250 /Users/sredfield/work/hst/cy23/somop/OP-cache/sopastphase2-v01.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14084 :visit-id "01" :proposal-version -1 :trans-version "20150609" :date "22-Jul-2015 14:56:14.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 279984 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14084 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14084 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2880 :al-overhead-at-end 0 :internal-dur-at-end 113 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3213 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14084 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2991 :al-overhead-at-end 194 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3213 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14084 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2991 :al-overhead-at-end 194 :internal-dur-at-end 319 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3213 :pcs-gap 0 ) true 3 0 SNR = 150.4102 Brightest Pixel = 7,047.32 e SNR = 16.0613 Brightest Pixel = 227.62 e Global Source Counts = 400,190.615 e SNR = 30.3158 Brightest Pixel = 361.09 e SNR = 26.5645 Brightest Pixel = 361.32 e SNR = 26.5645 Brightest Pixel = 361.32 e 1437591376738 /Users/sredfield/work/hst/cy23/somop/OP-cache/sopastphase2-v02.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14084 :visit-id "02" :proposal-version -1 :trans-version "20150609" :date "22-Jul-2015 14:56:16.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 279984 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14084 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14084 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2880 :al-overhead-at-end 0 :internal-dur-at-end 113 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3213 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14084 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2991 :al-overhead-at-end 194 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3213 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14084 :visit-id "02" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2991 :al-overhead-at-end 194 :internal-dur-at-end 319 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3213 :pcs-gap 0 ) true 3 0 SNR = 173.6203 Brightest Pixel = 11,990.92 e SNR = 75.7500 Brightest Pixel = 913.11 e Global Source Counts = 2,603,953.289 e SNR = 68.0688 Brightest Pixel = 1,725.97 e Using IUE Spectra: STIS.sp.733668 SNR = 59.7269 Brightest Pixel = 1,034.96 e Using Stellar Model Spectra: STIS.sp.733664 SNR = 26.0022 Brightest Pixel = 315.92 e Using IUE Spectra: STIS.sp.733668 SNR = 59.7269 Brightest Pixel = 1,034.96 e Using Stellar Model Spectra: STIS.sp.733664 SNR = 26.0022 Brightest Pixel = 315.92 e 1437591271218 /Users/sredfield/work/hst/cy23/somop/OP-cache/sopastphase2-v03.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14084 :visit-id "03" :proposal-version -1 :trans-version "20150609" :date "22-Jul-2015 14:54:31.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 88528 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14084 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14084 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2888 :al-overhead-at-end 0 :internal-dur-at-end 395 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3221 :pcs-gap 0 ) true 1 0 SNR = 150.3716 Brightest Pixel = 7,762.10 e SNR = 18.6840 Brightest Pixel = 197.54 e Global Source Counts = 405,576.268 e SNR = 17.9845 Brightest Pixel = 136.18 e 1437586407961 /Users/sredfield/work/hst/cy23/somop/OP-cache/sopastphase2-v04.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14084 :visit-id "04" :proposal-version -1 :trans-version "20150609" :date "22-Jul-2015 13:33:27.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 88528 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14084 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14084 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2888 :al-overhead-at-end 0 :internal-dur-at-end 395 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3221 :pcs-gap 0 ) true 1 0 SNR = 151.3525 Brightest Pixel = 7,859.98 e SNR = 18.8667 Brightest Pixel = 199.88 e Global Source Counts = 410,459.429 e SNR = 15.9530 Brightest Pixel = 111.07 e 1437591378182 /Users/sredfield/work/hst/cy23/somop/OP-cache/sopastphase2-v05.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14084 :visit-id "05" :proposal-version -1 :trans-version "20150609" :date "22-Jul-2015 14:56:17.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 279984 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14084 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14084 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2885 :al-overhead-at-end 0 :internal-dur-at-end 113 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3218 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14084 :visit-id "05" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2996 :al-overhead-at-end 194 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3218 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14084 :visit-id "05" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2996 :al-overhead-at-end 194 :internal-dur-at-end 319 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3218 :pcs-gap 0 ) true 3 0 SNR = 150.9974 Brightest Pixel = 8,204.82 e SNR = 19.3886 Brightest Pixel = 197.95 e Global Source Counts = 420,754.530 e SNR = 30.7134 Brightest Pixel = 372.10 e SNR = 20.9679 Brightest Pixel = 225.86 e SNR = 20.9679 Brightest Pixel = 225.86 e 1437586409364 /Users/sredfield/work/hst/cy23/somop/OP-cache/sopastphase2-v06.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14084 :visit-id "06" :proposal-version -1 :trans-version "20150609" :date "22-Jul-2015 13:33:29.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 88528 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14084 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14084 :visit-id "06" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2880 :al-overhead-at-end 0 :internal-dur-at-end 395 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3213 :pcs-gap 0 ) true 1 0 SNR = 150.9925 Brightest Pixel = 8,204.27 e SNR = 19.4995 Brightest Pixel = 199.40 e Global Source Counts = 423,843.197 e SNR = 16.2426 Brightest Pixel = 114.55 e 1437586410123 /Users/sredfield/work/hst/cy23/somop/OP-cache/sopastphase2-v07.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14084 :visit-id "07" :proposal-version -1 :trans-version "20150609" :date "22-Jul-2015 13:33:29.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 88528 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14084 :visit-id "07" :obset-id "07" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14084 :visit-id "07" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2885 :al-overhead-at-end 0 :internal-dur-at-end 395 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3218 :pcs-gap 0 ) true 1 0 SNR = 150.4547 Brightest Pixel = 8,587.85 e SNR = 22.4044 Brightest Pixel = 198.72 e Global Source Counts = 452,271.665 e SNR = 14.4657 Brightest Pixel = 92.52 e 1437586410872 /Users/sredfield/work/hst/cy23/somop/OP-cache/sopastphase2-v08.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14084 :visit-id "08" :proposal-version -1 :trans-version "20150609" :date "22-Jul-2015 13:33:30.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 88528 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14084 :visit-id "08" :obset-id "08" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14084 :visit-id "08" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2880 :al-overhead-at-end 0 :internal-dur-at-end 395 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3213 :pcs-gap 0 ) true 1 0 SNR = 150.5884 Brightest Pixel = 9,434.42 e SNR = 29.0649 Brightest Pixel = 170.62 e Global Source Counts = 547,985.194 e SNR = 25.6222 Brightest Pixel = 242.49 e