Status Report

NASA Hubble Space Telescope Daily Report #4184

By SpaceRef Editor
August 24, 2006
Filed under , ,
NASA Hubble Space Telescope Daily Report #4184
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT #4184

PERIOD COVERED: UT August 23, 2006 (DOY 235)

OBSERVATIONS SCHEDULED

ACS/HRC 10738

Earth Flats

Sky flats will be obtained by observing the bright Earth with the HRC and WFC. These observations will be used to verify the accuracy of the flats currently in the pipeline and to monitor any changes. Weekly coronagraphic monitoring is required to assess the changing position of the spots.

ACS/HRC 10805

ACS Imaging of Uranus’ Atmosphere Near Equinox

Uranus’ 97-degree spin axis inclination results in the largest fractional seasonal variation of solar insolation in the solar system. Uranus is now close to its 7 December 2007 equinox, and we can now see most of the northern hemisphere, which was in darkness when Voyager provided our first detailed view of the planet in 1986. If Uranus’ seasonal response has the large phase shift expected from its long radiative time constant, it should now exhibit nearly maximal hemispheric contrast. Although the long time constant also suggests a small physical response, significant hemispheric asymmetries in cloud structure and dynamics are becoming apparent. We propose a detailed characterization of Uranus’ current response to this forcing with a 10-orbit program consisting of 4 orbits of WFC imaging with narrowband ramp filters and 6 orbits of HRC imaging using both broadband and narrowband filters. Nine narrow-band filters between 0.62 and 0.955 microns will provide vertical sensing depths scanning through the pressure range where the putative methane and deeper H2S clouds might plausibly exist and provide strong constraints on their optical properties and parent gas mixing ratios. The high resolution HRC images will characterize the dynamics of discrete features at the 15-30 hour time scale unavailable from the ground. Short wavelength HRC images will enable a characterization of the stratospheric haze. These observations have unique combinations of spectral range and resolution with needed temporal and spatial resolution not available from groundbased observations.

ACS/HRC/WFC 10758

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. The files, biases and dark will be used to create reference files for science calibration. This programme will be for the entire lifetime of ACS. Changes from cycle 13:- The default gain for WFC is 2 e-/DN. As before bias frames will be collected for both gain 1 and gain 2. Dark frames are acquired using the default gain {2}. This program cover the period May, 31 2006- Oct, 1-2006. The first half of the program has a different proposal number: 10729.

ACS/SBC 10184

A New Class of Bright Ultraviolet Variable Sources in the Globular Cluster NGC 1851

Our reductions of archival STIS/FUV-MAMA data {AR9225} have discovered 13 completely unexpected and unexplained Ultraviolet bright variables. Eleven of the variables have been identified with evolved stars {Horizontal Branch or Asymptotic Giant Branch}. The total number and nature of these systems is completely unknown. If these variables are binaries the implication is that the binary fraction {up to 25%} in NGC 1851 is the highest in all Galactic globular clusters. The radial distributions of the variables and the blue horizontal branch stars imply a common origin and perhaps an explanation of the bi-modal morphology of the horizontal branch in the color magnitude diagrams of globular clusters. These variables may be the tip of the iceberg and a critical clue concerning the infamous “second parameter”. We propose to observe NGC 1851 on three occasions with the same setup as the archival data to determine the total number and periods of the ultraviolet variables.

ACS/WFC 10816

The Formation History of Andromeda’s Extended Metal-Poor Halo

We propose deep ACS imaging in the outer spheroid of the Andromeda galaxy, in order to measure the star formation history of its true halo. For the past 20 years, nearly all studies of the Andromeda “halo” were focused on the spheroid within 30 kpc of the galaxy’s center, a region now known to host significant substructure and populations with high metallicity and intermediate ages. However, two groups have recently discovered an extended metal-poor halo beyond 30 kpc; this population is distinct in its surface-brightness profile, abundance distribution, and kinematics. In earlier cycles, we obtained deep images of the inner spheroid {11 kpc on the minor axis}, outer disk {25 kpc on the major axis}, and giant tidal stream, yielding the complete star formation history in each field. We now propose deep ACS imaging of 4 fields bracketing this 30 kpc transition point in the spheroid, so that the inner spheroid and the extended halo populations can be disentangled, enabling a reconstruction of the star formation history in the halo. A wide age distribution in the halo, as found in the inner spheroid, would imply the halo was assembled through ongoing accretion of satellite galaxies, while a uniformly old population would be a strong indication that the halo was formed during the early rapid collapse of the Andromeda proto-galaxy.

ACS/WFC 10881

The Ultimate Gravitational Lensing Survey of Cluster Mass and Substructure

We propose a systematic and detailed investigation of the mass, substructure, and thermodynamics of one hundred X-ray luminous galaxy clusters at 0.15 < z < 0.3. The primary goal is to test our recent suggestion that this population is dominated by dynamically immature disturbed clusters, and that the observed mass-temperature relation suffers strong structural segregation. If confirmed, this would represent a paradigm shift in our observational understanding of clusters, that were hitherto believed to be dominated by mature, undisturbed systems. The key observation to this endeavor is Hubble imaging of cluster cores to identify robustly tangential and radial multiple arcs and measure the shape of faint galaxies. These strong and weak lensing signals will give an accurate measure of the total mass and structure of the dark matter distribution that we will subsequently compare with X-ray and Sunyaev Zeldovich Effect observables. The broader applications of our project include 1} the calibration of mass-temperature and mass-SZE scaling relations which will be critical for the calibration of proposed dark energy experiments, and 2} the low redshift baseline study of the demographics of massive clusters to aid interpretation of future high redshift {z>1} cluster samples. For this ultimate cluster survey, we request ACS SNAPSHOTS through the F606W filter drawn from a target list of 143 clusters.

ACS/WFC 10886

The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

As a continuation of the highly successful Sloan Lens ACS {SLACS} Survey for new strong gravitational lenses, we propose one orbit of ACS-WFC F814W imaging for each of 50 high- probability strong galaxy-galaxy lens candidates. These observations will confirm new lens systems and permit immediate and accurate photometry, shape measurement, and mass modeling of the lens galaxies. The lenses delivered by the SLACS Survey all show extended source structure, furnishing more constraints on the projected lens potential than lensed-quasar image positions. In addition, SLACS lenses have lens galaxies that are much brighter than their lensed sources, facilitating detailed photometric and dynamical observation of the former. When confirmed lenses from this proposal are combined with lenses discovered by SLACS in Cycles 13 and 14, we expect the final SLACS lens sample to number 80–100: an approximate doubling of the number of known galaxy-scale strong gravitational lenses and an order-of-magnitude increase in the number of optical Einstein rings. By virtue of its homogeneous selection and sheer size, the SLACS sample will allow an unprecedented exploration of the mass structure of the early-type galaxy population as a function of all other observable quantities. This new sample will be a valuable resource to the astronomical community by enabling qualitatively new strong lensing science, and as such we will waive all but a short {3-month} proprietary period on the observations.

ACS/WFC/NIC3 10632

Searching for galaxies at z>6.5 in the Hubble Ultra Deep Field

We propose to obtain deep ACS {F606W, F775W, F850LP} imaging in the area of the original Hubble Ultra Deep Field NICMOS parallel fields and – through simultaneous parallel observations – deep NICMOS {F110W, F160W} imaging of the ACS UDF area. Matching the extreme imaging depth in the optical and near-IR bands will result in seven fields with sufficiently sensitive multiband data to detect the expected typical galaxies at z=7 and 8. Presently no such a field exist. Our combined optical and near-IR ultradeep fields will be in three areas separated by about 20 comoving Mpc at z=7. This will allow us to give a first assessment of the degree of cosmic variance. If reionization is a process extending over a large redshift interval and the luminosity function doesn’t evolve strongly beyond z=6, these data will allow us to identify of the order of a dozen galaxies at 6.5 < z < 8.5 - using the Lyman break technique - and to place a first constrain on the luminosity function at z>6.5. Conversely, finding fewer objects would be an indication that the bulk of reionization is done by galaxies at z=6. By spending 204 orbits of prime HST time we will capitalize on the investment of 544 prime orbits already made on the Hubble Ultra Deep Field {UDF}. We have verified that the program as proposed is schedulable and that it will remain so even if forced to execute in the 2-gyro mode. The data will be non-proprietary and the reduced images will be made public within 2 months from the completion of the observations.

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.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration – CR Persistence Part 5

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.

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.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST:

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

17909-0 – Continuous Engineering Recording for Battery 4 BCT

COMPLETED OPS NOTES: (None)

                          SCHEDULED      SUCCESSFUL 
FGS GSacq                11                      11 
FGS REacq                04                      04 
OBAD with Maneuver   30                      30 

SIGNIFICANT EVENTS:

Battery 4 Capacity Test Flash Report # 3

Final Bat 4 capacity result for 2006: 57.5Ah @ 5A (53.5Ah @ 9A). Compare to 2004: 55.7Ah @ 5A (51.7 @ 9A).

SpaceRef staff editor.