0 Assigned ID: 741 ----- Attempting Submission 1 (Fri Apr 07 18:54:32 GMT 2017) ----- 0 ----- Attempting Submission 1 (Thu Jul 20 18:21:06 GMT 2017) ----- The OVI doublet in low-z QSO absorption systems can provide valuable constraints on the mass and physics of highly ionized gas in galaxy halos and the IGM. However, use of the OVI doublet is still hampered by uncertainty regarding the physical nature of these absorbers. Eight OVI absorption systems have been detected on the sight line to the low-redshift QSO H1821+643 with HST+STIS and FUSE. Careful inspection of these absorbers (observed with the STIS E140M echelle) reveals narrow peaks and inflections in the OVI profiles that are closely aligned with well-detected narrow HI and SiIII components at the same redshifts. This tentatively suggests that the OVI profiles contain narrow components at cool temperatures. However, the E140M spectral resolution is not adequate to constrain the line widths of these blended components accurately enough to support firm conclusions. We propose to use the E140H echelle mode of STIS to observe H1821+643 with ultra-high spectral resolution (R = 115,000) to place direct constraints on the temperature of the OVI-bearing gas based on the OVI line widths. We will also measure more precise centroids for the OVI, SiIII, and HI absorption components and more accurately decompose the multicomponent blends in many of the absorbers. In addition to probing the physics of extragalactic OVI systems, the spectra will provide a wealth of information about the Milky Way ISM and the low-redshift Lya forest. We will observe the QSO H1821+643 [z(QSO) = 0.297] with the E140H echelle mode of STIS. Motivated by a detailed communication with the STScI STIS Team, we will observe the target with the 0.2"x0.2" aperture in order to avoid throughput losses that can occur with the narrower apertures (see Proffitt et al. 2017, ISR STIS 2017-01). To use the telescope efficiently, we will observe the target in the continuous viewing zone (CVZ), which will allow us to use the majority of each orbit for science exposures. Following a recommendation from STScI, we will obtain two discrete science exposures in each orbit for good wavelength calibration (this will provide two wavelength calibration exposures in each orbit) and optimal buffer management. For this program, it is crucial to align individual spectra as well as possible (to avoid degradation of spectral resolution when the individual exposures are coadded to form the final spectrum). In principle, strong lines in the individual exposures can be used to align the spectra, but this can be difficult if the individual spectra are noisy. Therefore, we will execute an ACQ/PEAKUP procedure at the beginning of the first and third orbits in each visit to maintain optimal centering of the target in the aperture (and thereby maintain good alignment of the individual observations). We will record the science data in TIMETAG mode to enable improved data reduction procedures such as removal of data adversely affected by geocoronal emission (which can be more severe in CVZ observations). This target is known to be somewhat variable; photometry from the literature indicates that the QSO varies from V = 13.69 to 14.24. We have allowed for this variability in our exposure time calculations for acquisitions, peakups, and science exposures. Specifically, we have used the brightest known magnitudes to make sure that our exposures will not saturate if the target happens to be bright, but we have also selected exposure times that should enable successful acquisition even if the QSO turns out to be at the fainter end when the visits are executed (ETC details are provided in the Phase II exposure comments). Likewise, we have allowed for the possibility that the MAMA dark background "glow" could be high when these observations are obtained (CVZ observations tend to elevate the dark background as the observations within a visit progress). We have assumed the highest dark background levels in our ETC calculations of buffer times for the TIMETAG observations and in our bright-object checks for instrument safety. We find that this target does not pose any bright-object danger to the instrument, and following Figure 11.6 in the STIS Instrument Handbook, we find that the buffer dumps for the TIMETAG science exposures should be fully successful with buffer time = (exposure time)/2. Galaxies and the IGM 6 false false true false false false false SUPPORTED EXT-MEDIUM ABSORPTION LINE SYSTEM - EXTRAGALACTIC CORONAL GAS HOT GAS NO Photometry from the literature indicates that this source is somewhat variable with literature measurements ranging from Johnson V = 13.7 to Johnson V = 14.24 (with Pan-STARRS magnitudes in between these extremes). We have taken this variability into account in our calculations of acquisition and peakup exposure times as well as instrument safety assessment. J2000 J2000 Flambda(1300 A) = (6.0+/-0.25)e-14. Pan-STARRS mean mags: g = 14.071+/- 0.006, r = 13.977+/-0.005 STIS/FUV-MAMA Spectroscopic No No E140H 1343 STIS/FUV-MAMA Spectroscopic No No E140H 1343 STIS/FUV-MAMA Spectroscopic No No E140H 1343 STIS/FUV-MAMA Spectroscopic No No E140H 1416 1500581812740 /solaris/user1/dctaylor/proposals2/OP-cache/15321-v01.xml The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. 1525959242000 220.0 (Tic-Visit :proposal-id 15321 :visit-id "01" :proposal-version -1 :trans-version "20170613" :date "20-Jul-2017 16:16:51.0" :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 1844368 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15321 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 15321 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 27661 :al-overhead-at-end 0 :internal-dur-at-end 578 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) true 5 0 H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 9.67 seconds (STIS.ta.1009292), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 7.88 seconds with the 0.2x0.09 slit (STIS.ta.1012810), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Following recommendation from STScI, this peakup will recenter the target in the slit to guard against drift problems. H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 7.88 seconds with the 0.2x0.09 slit (STIS.ta.1012810), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. 1500581817259 /solaris/user1/dctaylor/proposals2/OP-cache/15321-v02.xml The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. 1530694240000 169.0 (Tic-Visit :proposal-id 15321 :visit-id "02" :proposal-version -1 :trans-version "20170613" :date "20-Jul-2017 16:16:56.0" :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 1844368 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15321 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 15321 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 27661 :al-overhead-at-end 0 :internal-dur-at-end 578 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) true 5 0 H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 9.67 seconds (STIS.ta.1009292), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 7.88 seconds with the 0.2x0.09 slit (STIS.ta.1012810), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Following recommendation from STScI, this peakup will recenter the target in the slit to guard against drift problems. H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 7.88 seconds with the 0.2x0.09 slit (STIS.ta.1012810), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. 1500581820811 /solaris/user1/dctaylor/proposals2/OP-cache/15321-v03.xml The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. 1535345662000 121.34058546303481 (Tic-Visit :proposal-id 15321 :visit-id "03" :proposal-version -1 :trans-version "20170613" :date "20-Jul-2017 16:17:00.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 1531264 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15321 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 15321 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 22084 :al-overhead-at-end 0 :internal-dur-at-end 440 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) true 4 0 H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 9.67 seconds (STIS.ta.1009292), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 7.88 seconds with the 0.2x0.09 slit (STIS.ta.1012810), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 640 counts/sec [STIS.sp.1013012]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 640 counts/sec [STIS.sp.1013012]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 640 counts/sec [STIS.sp.1013012]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 640 counts/sec [STIS.sp.1013012]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Following recommendation from STScI, this peakup will recenter the target in the slit to guard against drift problems. H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 7.88 seconds with the 0.2x0.09 slit (STIS.ta.1012810), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 640 counts/sec [STIS.sp.1013012]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. 1500581820811 /solaris/user1/dctaylor/proposals2/OP-cache/15321-v03.xml Repeat of failed visit 03. (Tic-Visit :proposal-id 15321 :visit-id "03" :proposal-version -1 :trans-version "20170613" :date "20-Jul-2017 16:17:00.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 1531264 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15321 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 15321 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 22084 :al-overhead-at-end 0 :internal-dur-at-end 440 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) false 4 0 H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 9.67 seconds (STIS.ta.1009292), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 7.88 seconds with the 0.2x0.09 slit (STIS.ta.1012810), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 640 counts/sec [STIS.sp.1013012]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 640 counts/sec [STIS.sp.1013012]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 640 counts/sec [STIS.sp.1013012]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 640 counts/sec [STIS.sp.1013012]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Following recommendation from STScI, this peakup will recenter the target in the slit to guard against drift problems. H1821+643 has been previously observed successfully with the STIS E140M mode and a narrow slit (see program 8165). We will use the same exposure times for the ACQ and ACQ/PEAKUP as the previous successful observation. However, literature photometry indicates that the target is somewhat variable with V band magnitudes ranging from V = 13.69 to 14.24. To ensure that the detector will not saturate, we have used the STIS acquistion ETC to check whether an exposure of 1.3 seconds poses a risk of detector saturation. We find that with V = 13.69, the detector will saturate after 7.88 seconds with the 0.2x0.09 slit (STIS.ta.1012810), so our requested exposure time of 1.3 seconds should be well below the danger of saturation. Similarly, the exposure time should allow for sucessful acquisition even if the target is on the faint end of the observed range when the observations are executed. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 640 counts/sec [STIS.sp.1013012]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used. Assuming STIS glow = high (i.e., warm detector and high dark rate) and highest observed UV flux from the QSO, STIS ETC indicates that the count rate for the entire detector = 742 counts/sec [STIS.sp.1012439]. Following Figure 11.6 in the STIS Instrument Handbook, this indicates that a buffer time = t(exp)/2 should be used.