Status Report

NASA Hubble Space Telescope Daily Report #4061

By SpaceRef Editor
March 3, 2006
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NASA Hubble Space Telescope Daily Report #4061

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: UT March 01, 2006 (DOY 060)



ACS UV Calibration Monitor and SBC Dark Current

A standard star field {NGC6681} is observed twice during cycle 13, alternating between after and before annealing operations, through all the ACS broad band UV filters. NGC6681 hosts several UV spectro – photometric standard stars for which accurate spectra have been {and will continue to be} measured. Four SBC dark current exposures taken as the last exposure of each SBC sequence.


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 Oct, 2 2005- May, 29-2006. The second half of the program has a different proposal number: 10758.

ACS/WFC 10515

The Unique Star Cluster System of M85

Even with its long history as one of the pillars of modern astronomy, the study of star clusters has continued to reveal new and surprising things. Over the past decade, numerous programs with HST have shown that extragalactic star clusters powerfully probe the processes of galactic formation, evolution, and destruction. The diversity of star cluster systems is a testament to the rich variation in galaxy properties. During the course of the ACS Virgo Cluster Survey, we have discovered that the early-type galaxy M85 has a system of star clusters unlike any other galaxy studied to date. Hundreds of star clusters in M85 are fainter and more extended than typical globular clusters, and have no local analog. We propose deep optical- infrared imaging with ACS and NICMOS to obtain ages, metallicities, luminosities, and sizes of unprecedented precision to characterize these new star clusters and unravel the evolutionary state of M85 that gave rise to them.

ACS/WFC 10543

Microlensing in M87 and the Virgo Cluster

Resolving the nature of dark matter is an urgent problem. The results of the MACHO survey of the Milky Way dark halo toward the LMC indicate that a significant fraction of the halo consists of stellar mass objects. The VATT/Columbia survey of M31 finds a similar lens fraction in the M31 dark halo. We propose a series of observations with ACS that will provide the most thorough search for microlensing toward M87, the central elliptical galaxy of the Virgo cluster. This program is optimized for lenses in the mass range from 0.01 to 1.0 solar masses. By comparing with archival data, we can detect lenses as massive as 100 solar masses, such as the remnants of the first stars. These observations will have at least 15 times more sensitivity to microlensing than any previous survey, e.g. using WFPC2. This is due to the factor of 2 larger area, factor of more than 4 more sensitivity in the I-band, superior pixel scale and longer baseline of observations. Based on the halo microlensing results in the Milky Way and M31, we might expect that galaxy collisions and stripping would populate the overall cluster halo with a large number of stellar mass objects. This program would determine definitively if such objects compose the cluster dark matter at the level seen in the Milky Way. A negative result would indicate that such objects do not populate the intracluster medium, and may indicate that galaxy harassment is not as vigorous as expected. We can measure the level of events due to the M87 halo: this would be the best exploration to date of such a lens population in an elliptical galaxy. Star-star lensing should also be detectable. About 20 erupting classical novae will be seen, allowing to determine the definitive nova rate for this giant elliptical galaxy. We will determine if our recent HST detection of an M87 globular cluster nova was a fluke, or indicative of a 100x higher rate of incidence of cataclysmic variables and nova eruptions in globulars than previously believed. We will examine the populations of variable stars, and will be able to cleanly separate them from microlensing.

ACS/WFC 10775

An ACS Survey of Galactic Globular Clusters

We propose to conduct an ACS/WFC imaging survey of Galactic globular clusters. We will construct the most extensive and deepest set of photometry and astrometry to-date for these systems reaching a main sequence mass of ~0.2 solar mass with S/N >= 10. We will combine these data with archival WFPC2 and STIS images to determine proper motions for the stars in our fields. The resultant cleaned cluster CMDs will allow us to study a variety of scientific questions. These include [but are not limited to] 1} the determination of cluster ages and distances 2} the construction of main sequence mass functions and the issue of mass segregation 3} the internal motions and dynamical evolution of globular clusters, and 4} absolute cluster motions, orbits, and the Milky Way gravitational potential. We anticipate that the unique resource provided by the proposed treasury archive will play a central role in the field of globular cluster studies for decades, with a stature comparable to that of the Hubble Deep Field for high redshift studies.

FGS 10610

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 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.


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


10154 – GSacq(2,1,2) resulted in fine lock backup using FGS 1 @ 060/10:53:45z

GSacq(2,1,2) scheduled at 060/10:50:04 resulted in fine lock backup (1,0,1) due to scan step limit exceeded on FGS 2.

10155 – GSACQ(2,1,2) fine lock backup, scan step limit exceeded on FGS 2 @ 060/14:07:15z

Upon acquisition of signal at 060/14:07:15 HST was in fine lock on FGS 1 only. GSACQ(2,1,2) at 060/13:59:06 ended in fine lock backup on FGS 1 due to scan step limit exceeded on FGS 2.

10156 – OBAD Failure @ 060/15:25:37z

OBAD at 15:23:31 on FHST 2 and 3 failed with very high reported error correction (-149739.53, -68756.24, -165672.15, RSS= 233659.19). Status buffer message 1806 “T2G Open Loop Timeout” occurred at 15:25:37. Status Buffer message 1902 “OBAD Failed Identification” was received at 15:26:20. Subsequent OBAD at 15:41:03 had no telemetry but HST was in fine lock at 16:20:47 AOS.


                           SCHEDULED      SUCCESSFUL      FAILURE TIMES
FGS GSacq                 10                      10
FGS REacq                 02                       02
OBAD with Maneuver    26                       25                 Hstar # 10156


SpaceRef staff editor.