Status Report

NASA Hubble Space Telescope Daily Report #4183

By SpaceRef Editor
August 23, 2006
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NASA Hubble Space Telescope Daily Report #4183

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: UT August 22, 2006 (DOY 234)



An Efficient ACS Coronagraphic Survey for Debris Disks around Nearby Stars

We propose to finish our Cycle 11 optical survey for nearby debris disks using the ACS/HRC coronagraph. Out of 43 orbits originally proposed for the survey, 23 orbits were allocated, leading to a survey of 22 stars, from which two new debris disks were imaged for the first time. Our analysis of the initial survey gives an empirical estimate for the detection rate of debris disks relative to heliocentric distance and dust optical depth. Our target list for Cycle 15 is now optimized to yield more frequent disk detections. Likewise our observing strategy is improved to maximize sensitivity per telescope orbit allocated. Therefore we present the most efficient survey possible. The scientific motivation is to obtain scattered light images of previously unresolved debris disks to determine their viewing geometry and physical architecture, both of which may characterize the underlying planetary system. We choose 25 debris disk targets for which we predict a detection rate of 25% ? 5%. Four targets have extrasolar planets from which the viewing geometry revealed by a disk detection will resolve the v sin{i} ambiguity in the planet masses. These targets present the remarkable opportunity of finally seeing a debris disk in system with known planets.

ACS/SBC 10739

Internal Flat Field Stability

The stability of the CCD flat fields will be monitored using the calibration lamps and a sub-sample of the filter set. For the SBC imaging filters, differences in the low-frequency flat field structure with wavelength will be assessed. New high signal P-flats will be obtained for the SBC prisms.

ACS/WFC 10421

Searching for Ancient Mergers in Early Type Host Galaxies of Classical QSOs

Recent HST imaging of QSO host galaxies indicates that at least a large fraction of QSOs reside in seemingly undisturbed elliptical hosts. However, our deep Keck spectroscopy of a sample of these host galaxies indicates that many of these objects were involved in a major starburst episode between 0.6 and 1.6 Gyr ago. We propose to obtain very deep ACS WFC observations of the five hosts in this sample that have the most reliable age determinations to search for fine structure indicative of a past merger event and to test the hypothesis that the elliptical hosts are the products of relatively recent merger events rather than old galaxies which formed at high redshifts. By establishing a firm connection between ancient mergers and the aging starbursts in these classical QSOs, we will be able to estimate the fraction of the total QSO population that results directly from mergers accompanied by massive starbursts and to place constraints on the duty cycle for QSO activity.

ACS/WFC 10595

A Reference Database for Accurate Ages and Metallicities of Globular Clusters in the Magellanic Clouds

We propose to finalize the compilation of a comprehensive database of high-quality ages and metallicities of Simple Stellar Populations {SSPs} in the Milky Way and the Magellanic Clouds. We will acquire new ACS imagery for 8 young and intermediate-age globular clusters in the Magellanic Clouds to create high-quality color-magnitude diagrams {CMDs} to enable accurate measurements of their ages and metallicities. In concert with a similar analysis of CMD data already available in the HST archive for 8 more such GCs, the resulting database will provide a well-sampled coverage of the full range of ages and metallicities known among globular clusters {0.5 <= Age {Gyr} <= 13.5 and -2.3 <= [Fe/H] <= +0.1, respectively}. This database will form the crucial basis for our ongoing, comprehensive multi-wavelength program to: {1} establish empirical relations among SSP colors {from the UV [GALEX] through the mid-IR [Spitzer]}, line strengths, ages and metallicities, and {2} provide a stringent test of the systemic accuracy of age and metallicity determinations using state-of-the-art population synthesis models.


Archaeology of Fossil Galaxy Groups

Fossil groups are concentrations of dark matter with masses and x-ray luminosities comparable to those of an entire group of galaxies, but whose light is dominated by a single, isolated, large elliptical galaxy. The origin of these systems remains a puzzle: they may be the end products of complete merging of galaxies within once normal groups, or they might originate from a very unusual galaxy luminosity function in those regions that inhibits the formation of moderate-sized galaxies. We propose the first study of the globular cluster populations of the dominant elliptical galaxies in fossil galaxy groups, which will provide important new insights into their origin.

FGS 10989

Astrometric Masses of Extrasolar Planets and Brown Dwarfs

We propose observations with HST/FGS to estimate the astrometric elements {perturbation orbit semi-major axis and inclination} of extra-solar planets orbiting six stars. These companions were originally detected by radial velocity techniques. We have demonstrated that FGS astrometry of even a short segment of reflex motion, when combined with extensive radial velocity information, can yield useful inclination information {McArthur et al. 2004}, allowing us to determine companion masses. Extrasolar planet masses assist in two ongoing research frontiers. First, they provide useful boundary conditions for models of planetary formation and evolution of planetary systems. Second, knowing that a star in fact has a plantary mass companion, increases the value of that system to future extrasolar planet observation missions such as SIM PlanetQuest, TPF, and GAIA.

WFPC2 10744

WFPC2 Cycle 14 Decontaminations and Associated Observations

This proposal is for the WFPC2 decons. Also included are instrument monitors tied to decons: photometric stability check, focus monitor, pre- and post-decon internals {bias, intflats, kspots, & darks}, UV throughput check, VISFLAT sweep, and internal UV flat check.


Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)


10408 GSAcq(1,2,1) requires two attempts to achieve CT-DV @ 230/05:33:42z

GSAcq(1,2,1),required two attempts to achieve CT-DV on FGS1. The acquisition was succesful.


17898-0 Battery 4 Capacity Test Script & 5 Battery Pressure Limit COP (Thru step 18)


                          SCHEDULED      SUCCESSFUL 
FGS GSacq                 07                    07 
FGS REacq                 07                    07 
OBAD with Maneuver    28                    28 


Battery 4 Capacity Test Flash Report #1

Commanding for the Battery 4 Capacity Test started as scheduled on DOY 234/1411 GMT (08/22 at 10:11 am) with setting the Battery Pressure Test for a 5-battery system. Battery 4 was taken off-line and started discharging on the first opportunity at 1503 GMT (11:03 am). The discharge is expected to continue for approximately 48 hours with the switch from high-rate to the low-rate discharge resistor occurring Tuesday evening. Following completion of the discharge. Battery 4 will be placed back online in hardware during orbit night. Following its recovery period, Battery 4 will be placed back on-line in FSW.

Battery 4 Capacity Test Flash Report #2

At approximately DOY 2006/235 00:41 GMT (08/22/06 at 8:41 pm local), the battery 4 discharge transitioned from the high rate resistor to the low rate resistor. The discharge continues nominally with battery temperatures cycling below 5 DegC.

SpaceRef staff editor.