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Daily 3681
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT # 3681 PERIOD COVERED: DOY 237 OBSERVATIONS SCHEDULED ACS/HRC/WFC 10061 CCD Daily Monitor This program consists of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. This programme will be executed once a day for the entire lifetime of ACS. ACS/WFC 10158 ACS Observations of the Gravitational Lens B1608+656: Characterizing the Einstein Ring We request time to obtain ACS deep images of the B1608+656 gravitational lens system to fully characterize its enclosing Einstein ring with high signal-to-noise ratio {SNR}. These data will allow us to determine the gravitational potential of the lens, locally, to several percent accuracy and, combined with the three independent time delays, measure H_0 to much better than 10% precision. For this goal, we have developed powerful new lens modeling codes that make use of the full brightness distribution of the Einstein ring in lens systems. The B1608+656 system is ideal for our new code. It has precisely measured time delays, a well-determined stellar velocity dispersion, and an Einstein ring that is not dominated by the lensed nuclear emission of the background source. When combined with high-SNR images of Einstein rings, the new modeling codes provide qualitatively different and much improved analysis of the ring emission than was previously possible. The proposed ACS observations will reach the SNR at which the new modeling code can be fully exploited {SNR=5 per pixel}. Our simulations show that these new data will allow us to reduce the total uncertainties in H_0 derived from the system by at least a factor of two, to the 5-7% level for this system. ACS/WFC 10178 Imaging Polarimetry of Young Stellar Objects with ACS and NICMOS: A study in dust grain evolution The formation of planetary systems is intimately linked to the dust population in circumstellar disks, thus understanding dust grain evolution is essential to advancing our understanding of how planets form. By combining {1} the high resolution polarimetric capabilities of ACS and NICMOS, {2} powerful 3-D radiative transfer codes, and {3} observations of objects known to span the earliest stellar evolutionary phases, we will gain crucial insight into the initial phases of dust grain growth: evolution away from an ISM distribution. Fractional polarization is a strong function of wavelength, therefore by comparing polarimetric images in the optical and infrared, we can sensitively constrain not only the geometry and optical depth of the scattering medium, but also the grain size distribution. By observing objects representative of the earliest evolutionary sequence of YSOs, we will be able to investigate how the dust population evolves in size and distribution during the crucial transition from a disk+envelope system to a disk+star system. The proposed study will help to establish the fundamental time scales for the initial depletion of ISM-like grains: the first step in understanding the transformation from small submicron sized dust grains, to large millimeter sized grains, and untimely to planetary bodies. FGS 10110 Parallaxes of Extreme Halo Subgiants: Calibrating Globular Cluster Distances and the Ages of the Oldest Stars The ages of the oldest stars are a key constraint on the evolution of our Galaxy, the history of star formation, and cosmological models. These ages are usually determined from globular clusters. However, it is alternatively possible to determine ages of extreme Population II subgiants in the solar neighborhood based on trigonometric parallaxes, without any recourse to clusters. This approach completely avoids the vexing issues of cluster distances, reddenings, and chemical compositions. There are 3 known nearby, extremely metal-deficient Pop II subgiants with Hipparcos parallax errors of 6-11% which are available for such age determinations. At present, based on the latest isochrones, the derived ages of these stars {HD 84937, HD 132475, and HD 140283} are all close to 14 Gyr, uncomfortably close to or higher than current estimates of the age of the universe. However, the errors in the Hipparcos parallaxes imply uncertainties of at least 2 Gyr in the ages of the 3 stars. We propose to measure parallaxes of these three Pop II subgiants using HST's Fine Guidance Sensor 1R. We expect to reduce the Hipparcos parallax error bars by factors of 5-6, providing the most stringent test yet of current theoretical stellar models of Pop II stars and pushing the age uncertainties to below 0.5 Gyr. These data will also provide a major new constraint on the distance scale of globular clusters, with wide implications for stellar evolution and the calibration of Pop II standard candles. NIC1/NIC2/NIC3 8793 NICMOS Post-SAA calibration - CR Persistence Part 4 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 USEAFTER 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 DARKSs. 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. NIC2 9752 A Search for the Exciting Sources in OMC-1 through NICMOS Polarization Measurements Orion contains the site of the nearest region of massive star formation to the Sun; only here can this pivotal process in galactic evolution be studied at the highest resolution. There are 10^5 solar luminosities of radiation emitted from the Orion Molecular Cloud {OMC-1}, possibly from a young massive star or protostar, or possibly from several, less luminous sources. Either way, the powering source{s} in the closest site of massive star formation has still not yet been identified. Here we propose to apply a new tool to determine which, of several prospective sources, might prove to be the heart of OMC-1. The sources cannot be seen directly because they lie in, or behind, a warm, dense molecular cloud. However, their presence can be inferred in polarized light, through the manner in which light is scattered off neighboring clouds. Heretofore, the spatial resolution has not been adequate to identify the locations of individual stars. We propose to use the NICMOS polarizers combined with the high spatial resolution of HST to achieve this, in spite of the high density of candidate objects in the core of Orion. The demands of accurately measuring the polarization vectors of small, diffuse objects relative to the surrounding background from dust-scattered light requires the high Strehl ratio and stable point-spread function only achievable from space. NIC2 9867 How Do Brown Dwarfs Form? With NICMOS/NIC2 imaging of five brown dwarfs and one low mass star that we have identified in a young cluster in OMC2/3, we plan to assess the similarities between brown dwarf formation and low mass star formation by searching for the presence of shocked H2 line emission from jets/outflows, close binary companions, and/or reflection nebulosity from protostellar envelopes and outflow cavities. The detection of these phenomena would be evidence that brown dwarfs result from the continuation of the star formation process to masses below the hydrogen burning limit, and not through the dynamical ejection of stellar embryos as has been recently proposed. This proposal is complementary to our SIRTF GTO program designed to search for circumstellar disks by measuring the spectral energy distribution of these sources out to 8 microns. This task requires not only high spatial resolution, but also a stable, unchanging PSF such as HST provides. WFPC2 10071 WFPC2 CYCLE 12 Supplemental Darks Part 3/3 This dark calibration program obtains 3 dark frames every day to provide data for monitoring and characterizing the evolution of hot pixels. FLIGHT OPERATIONS SUMMARY: Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.) HSTAR 9522: GS Acquisition (1,2,1) @ 237/17:35:52Z failed to RGA control due to SRLE on FGS 1. Two FHST FM Updates scheduled prior to the GS acquisition both occurred during LOS, however they both succeeded and the second on had a very low vehicle error observed at AOS. The T2 Slew scheduled @ 237/17:19:57Z had a slew angle of 37.427 degrees. The Search Radius for the GS Acquisition was 55 arcsec. FHST Map @ 237/17:43:26Z showed errors of 1.840, -2.830, and 11.177 arcsec. Under investigation. COMPLETED OPS REQs: None OPS NOTES EXECUTED: 1260-0 Table Dump @ 237/16:00z 1262-0 Lower STIS Bulkhead 6 Temperature 00BBH6T @ 238/01:53z SCHEDULED SUCCESSFUL FAILURE TIMES FGS GSacq 08 07 See Hstar # 9522 FGS REacq 07 07 FHST Update 11 11 LOSS of LOCK SIGNIFICANT EVENTS: Battery 3 Capacity Test continues. Continuous ESTR Engineering Coverage during Battery 3 Capacity Test. |
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