Status Report

NASA Hubble Space Telescope Daily Report #4935

By SpaceRef Editor
September 22, 2009
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Continuing to Collect World Class Science

PERIOD COVERED: 5am September 21 5am September 22, 2009 (DOY 264/09:00z-265/09:00z)


ACS/WFC3 11879

CCD Daily Monitor (Part 1)

This program comprises basic tests for measuring the read noise and dark current of the ACS WFC and for tracking the growth of hot pixels. The recorded frames are used to create bias and dark reference images for science data reduction and calibration. This program will be executed four days per week (Mon, Wed, Fri, Sun) for the duration of Cycle 17. To facilitate scheduling, this program is split into three proposals. This proposal covers 352 orbits (22 weeks) from 31 August 2009 to 31 January 2010.


Photometric Cross-Calibration using Stellar Flux Standards

The purpose of this proposal is to: A) Verify the ACS HRC and WFC photometric calibrations with a repeat visit to one of the three primary WDs. B) Measure the change in sensitivity with time for bright stars (which would include any small CTE contributions). C) Continue to investigate the ~2% discrepancy between ACS flux calibration and that of STIS (ACS ISR 2007-06). The goal is to measure any filter bandpass shifts in ACS or rule out the possibility of shifts as the primary contributors to the ACS/STIS discrepancy for cool stars.

COS/FUV 11895

FUV Detector Dark Monitor

The purpose of this proposal is to monitor the FUV detector dark rate by taking long science exposures without illuminating the detector. The detector dark rate and spatial distribution of counts will be compared to pre-launch and SMOV data in order to verify the nominal operation of the detector. Variations of count rate as a function of orbital position will be analyzed to find dependence of dark rate on proximity to the SAA. Dependence of dark rate as function of time will also be tracked.

FGS 11704

The Ages of Globular Clusters and the Population II Distance Scale

Globular clusters are the oldest objects in the universe whose age can be accurately determined. The dominant error in globular cluster age determinations is the uncertain Population II distance scale. We propose to use FGS 1R to obtain parallaxes with an accuracy of 0.2 milliarcsecond for 9 main sequence stars with [Fe/H] < -1.5. This will determine the absolute magnitude of these stars with accuracies of 0.04 to 0.06mag. This data will be used to determine the distance to 24 metal-poor globular clusters using main sequence fitting. These distances (with errors of 0.05 mag) will be used to determine the ages of globular clusters using the luminosity of the subgiant branch as an age indicator. This will yield absolute ages with an accuracy of 5%, about a factor of two improvement over current estimates. Coupled with existing parallaxes for more metal-rich stars, we will be able to accurately determine the age for globular clusters over a wide range of metallicities in order to study the early formation history of the Milky Way and provide an independent estimate of the age of the universe. The Hipparcos database contains only 1 star with [Fe/H] < -1.4 and an absolute magnitude error less than 0.18 mag which is suitable for use in main sequence fitting. Previous attempts at main sequence fitting to metal-poor globular clusters have had to rely on theoretical calibrations of the color of the main sequence. Our HST parallax program will remove this source of possible systematic error and yield distances to metal- poor globular clusters which are significantly more accurate than possible with the current parallax data. The HST parallax data will have errors which are 10 times smaller than the current parallax data. Using the HST parallaxes, we will obtain main sequence fitting distances to 11 globular clusters which contain over 500 RR Lyrae stars. This will allow us to calibrate the absolute magnitude of RR Lyrae stars, a commonly used Population II distance indicator. COS/NUV 11476 COS NUV External Spectroscopic Performance – Part 1 The goal of this project is to measure the spectral resolution of absorption lines for each of the four COS NUV gratings. We will acquire science data at the central wavelength of each grating through both PSA and BOA apertures. We will also evaluate the effect of small pointing errors on the spectral resolution by acquiring additional spectra at spatially offset positions. The targets chosen for these observations have sharp absorption lines and will be either unresolved or marginally resolved at the COS resolution. Our observations with the PSA will target the subdwarf B star Feige 48 (PG 1144+651). The observations with the BOA will be performed on the bright O subdwarf BD+75D325, a bright (M_V = 9.6) HST calibration standard. COS/NUV 11477 COS NUV External Spectroscopic Performance – Part 2 The goal of this activity is to verify the spatial resolution of COS in the NUV and to characterize the interdependence of the spatial and spectral resolution of the instrument in that wavelength band. By stepping the source along the cross-dispersion direction out to the edge of the PSA, we will be able to quantify the variation of the spatial profile of the source with off-axis position, both by measuring the shape and width of the profile and by measuring the amount of flux transmitted through the aperture as the source is stepped past the edge of the aperture. Aside from measuring the spatial resolution of COS spectra, this study will be particularly useful for characterizing the contamination of sources near the targeted object in crowded stellar fields. This test is ideally performed with a spatially unresolved point source with an emission line spectrum. Our observations with the PSA will target the Galactic symbiotic stars AG Draconis and He 2-38. Our observations with the BOA will target another Galactic symbiotic star, RR Telescopii. This object exhibits similar line widths to AG Dra, but includes a rich array of Fe II emission lines as well. COS/NUV/FUV/WFC3/UVIS/IR 11520 COS-GTO: QSO Absorbers, Galaxies and Large-Scale Structures in the Local Universe This is a program to probe the large scale structure of baryons in the universe, including addressing questions of baryon fraction, physical conditions and relationships between absorbers and large-scale structures of galaxies. Besides these specific goals, this proposed GTO program also probes a large enough total path length in Ly alpha and OVI to add significantly to what STIS/FUSE has already observed. Several Galactic High Velocity Cloud Complexes also are probed by these sightlines, particularly the M Complex. The total path length of this proposed program for Ly alpha large-scale structure surveys is delta_z~5.5. We have selected a variety of targets to address these questions, under the following subcategories: 1. Target 8 bright BL Lac objects to search for low contrast Ly alpha absorbers from the warm-hot interstellar medium (WHIM). 2. Ly alpha cloud sizes: The targets are a bright AGN pair which yield tangential distance separations of 100–500 kpc at z=0.01–0.05, where galaxy surveys are excellent. This pair has two filaments and two voids in this distance range. 3. Probes of starburst outflows: The targets are bright AGN, <= 100 kpc in projection out of the minor axis of nearby starburst galaxies. 4. A large galaxy’s gaseous halo: Three probes of the kinematics and metallicity of a single L* galaxy halo. These observations includes G130M, G160M exposures at SNR~20 and G285M at 2850A and SNR~10 for MgII. The 2L* galaxy, ESO 157-G049 (cz=1678 km/s), being probed by these sightlines has an available H I 21cm map from ATCA, H alpha imaging from CTIO and long-slit spectra from MSSSO. 5. Dwarf galaxy winds: These targets probe the kinematics and metallicities of outflows from active and inactive (in terms of star formation) dwarfs. NIC1/NIC2/NIC3 11947 Extended Dark Monitoring This program takes a series of darks to obtain darks (including amplifier glow, dark current, and shading profiles) for all three cameras in the read-out sequences used in Cycle 17. A set of 12 orbits will be observed every two months for a total of 72 orbits for a 12 month Cycle 17. This is a continuation of Cycle 16 program 11330 scaled down by ~80%. The first orbit (Visit A0) should be scheduled in the NICMOS SMOV after the DC Transfer Test (11406) and at least 36h before the Filter Wheel Test (11407). Data download using fast track. The following 28 orbits (visit A1-N2) should be scheduled AFTER the SMOV Proposal 11407 (Filter Wheel Test). This is done in order to monitor the dark current following an adjustment of the NCS set-point. These visits should be executed until the final temperature is reached during SMOV. NIC1/NIC2/NIC3 8795 NICMOS Post-SAA Calibration – CR Persistence Part 6 This is a new procedure proposed to alleviate the CR-persistence problem of NICMOS. Dark frames will be obtained immediately upon exiting the SAA contour 23, and every time a NICMOS exposure is scheduled within 50 minutes of coming out of the SAA. The darks will be obtained in parallel in all three NICMOS cameras. The post-SAA darks will be non-standard reference files available to users with a ‘Use After’ date/time mark. The keyword ‘UseAfter=date/time’ will also be added to the header of each post-SAA dark frame. The keyword must be populated with the time, in addition to the date, because HST crosses the SAA ~8 times per day, so each post-SAA dark will need to have the appropriate time specified, for users to identify the ones they need. Both the raw and processed images will be archived as post-SAA darks. Generally we expect that all NICMOS science/calibration observations started within 50 minutes of leaving an SAA will need such MAPs to remove the CR persistence from the science images. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors. STIS/CCD 11844 CCD Dark Monitor Part 1 The purpose of this proposal is to monitor the darks for the STIS CCD. STIS/CCD 11846 CCD Bias Monitor-Part 1 The purpose of this proposal is to monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns. STIS/CCD 11852 STIS CCD Spectroscopic Flats C17 The purpose of this proposal is to obtain pixel-to-pixel lamp flat fields for the STIS CCD in spectroscopic mode. STIS/CCD 11853 Cycle 17 STIS CCD Imaging Flats This program periodically monitors the STIS CCD imaging mode flat fields by using the tungsten lamps. STIS/MA1/MA2 11857 STIS Cycle 17 MAMA Dark Monitor This proposal monitors the behavior of the dark current in each of the MAMA detectors. The basic monitor takes two 1380s ACCUM darks each week with each detector. However, starting Oct 5, pairs are only included for weeks that the LRP has external MAMA observations planned. The weekly pairs of exposures for each detector are linked so that they are taken at opposite ends of the same SAA free interval. This pairing of exposures will make it easier to separate long and short term temporal variability from temperature dependent changes. For both detectors, additional blocks of exposures are taken once every six months. These are groups of five 1314s FUV-MAMA Time-Tag darks or five 3x315s NUV ACCUM darks distributed over a single SAA-free interval. This will give more information on the brightness of the FUV MAMA dark current as a function of the amount of time that the HV has been on, and for the NUV MAMA will give a better measure of the short term temperature dependence. WFC3/ACS/UVIS 12007 Supernova Follow up This proposal is one orbit to follow up discovery of a supernova. WFC3/IR 11936 IR Grism Flux Calibration This program will determine image displacement, spectral trace and flux calibration for the IR G102 and G141 grisms as a function of spatial position within the field of view. The HST flux standard GD71 will be observed in a 9-point pattern in the IR field of view, which will provide the necessary image displacement, spectral trace, and throughput measurements. WFC3/UVIS 11565 A Search for Astrometric Companions to Very Low-Mass, Population II Stars We propose to carry out a Snapshot search for astrometric companions in a subsample of very low-mass, halo subdwarfs identified within 120 parsecs of the Sun. These ultra-cool M subdwarfs are local representatives of the lowest-mass H burning objects from the Galactic Population II. The expected 3-4 astrometric doubles that will be discovered will be invaluable in that they will be the first systems from which gravitational masses of metal-poor stars at the bottom of the main sequence can be directly measured. WFC3/UVIS 11905 WFC3 UVIS CCD Daily Monitor The behavior of the WFC3 UVIS CCD will be monitored daily with a set of full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K subarray biases are acquired at less frequent intervals throughout the cycle to support subarray science observations. The internals from this proposal, along with those from the anneal procedure (Proposal 11909), will be used to generate the necessary superbias and superdark reference files for the calibration pipeline (CDBS). FLIGHT OPERATIONS SUMMARY: Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.) HSTARS: 12017 – GSAcq (2,3,3), scheduled from 265/07:54:41z – 265/08:01:24z, failed due to Search Radius Limit Exceeded on FGS3. Observations affected: COS 117 & 118, Proposal ID# 11895 & Astrometry Proposal ID# 11704 COMPLETED OPS REQUEST: 18562-1 – Continuous FGS Loss Of Lock looping @ 265/0825z COMPLETED OPS NOTES: (None)

FGS GSAcq 7 6
FGS REAcq 7 7
OBAD with Maneuver 6 6


SpaceRef staff editor.