Status Report

NASA Hubble Space Telescope Daily Report #4059

By SpaceRef Editor
February 28, 2006
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NASA Hubble Space Telescope Daily Report #4059

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science


PERIOD COVERED: UT February 27, 2006 (DOY 058)


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 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 10496

Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters

We propose a novel HST approach to obtain a dramatically more useful “dust free” Type Ia supernovae {SNe Ia} dataset than available with the previous GOODS searches. Moreover, this approach provides a strikingly more efficient search-and-follow-up that is primarily pre- scheduled. The resulting dark energy measurements do not share the major systematic uncertainty at these redshifts, that of the extinction correction with a prior. By targeting massive galaxy clusters at z > 1 we obtain a five-times higher efficiency in detection of Type Ia supernovae in ellipticals, providing a well-understood host galaxy environment. These same deep cluster images then also yield fundamental calibrations required for future weak lensing and Sunyaev-Zel’dovich measurements of dark energy, as well as an entire program of cluster studies. The data will make possible a factor of two improvement on supernova constraints on dark energy time variation, and much larger improvement in systematic uncertainty. They will provide both a cluster dataset and a SN Ia dataset that will be a longstanding scientific resource.

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.

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.

NIC3 10780

The Unusual Afterglow and Host Galaxy of the Short GRB 060121

We request Director’s Discretionary Time to observe the afterglow and host galaxy of the short- hard gamma-ray bursts GRB 060121. This is only the fourth time an optical afterglow of a short- hard burst has been found at its properties are significantly different to other cases. Both the afterglow and host galaxy are much fainter than previous short bursts {for which optical afterglows have been located} and the afterglow may also show the signature of dust extinction. Such extinction is completely unexpected for short bursts, given the currently popular model of their origin in NS-NS mergers. We propose ACS and NICMOS observations which will locate the afterglow and host galaxy of GRB 060121, provide constraints on its beaming angle, search for the signature of dust, and measure the offset from its host. These observations offer a strong test of NS-NS merger models.

WFPC2 10748

WFPC2 CYCLE 14 Standard Darks

This dark calibration program obtains dark frames every week in order to provide data for the ongoing calibration of the CCD dark current rate, and to monitor and characterize the evolution of hot pixels. Over an extended period these data will also provide a monitor of radiation damage to the CCDs.

WFPC2 10749

Earth Flats

This proposal monitors flatfield stability. This proposal obtains sequences of Earth streak flats to construct high quality flat fields for the WFPC2 filter set. These flat fields will allow mapping of the OTA illumination pattern and will be used in conjuction with previous internal and external flats to generate new pipeline superflats. These Earth flats will complement the Earth flat data obtained during cycles 4-13.

WFPC2 10750

WFPC2 Cycle 14 UV Earth Flats

Monitor flat field stability. This proposal obtains sequences of earth streak flats to improve the quality of pipeline flat fields for the WFPC2 UV filter set. These Earth flats will complement the UV earth flat data obtained during cycles 8-13.

WFPC2 10751

WFPC2 CYCLE 14 Intflat Linearity Check and Filter Rotation Anomaly Monitor

Intflat observations will be taken to provide a linearity check: the linearity test consists of a series of intflats in F555W, in each gain and each shutter. A combination of intflats, visflats, and earthflats will be used to check the repeatability of filter wheel motions. {Intflat sequences tied to decons, visits 1-18 in prop 10363, have been moved to the cycle 14 decon proposal 10744 for easier scheduling.} Note: long-exposure WFPC2 intflats must be scheduled during ACS anneals to prevent stray light from the WFPC2 lamps from contaminating long ACS external exposures.

WFPC2 10778

WFPC2 WF4 Supplemental Darks

An anomaly has been found in images from the WF4 CCD in WFPC2. The WF4 CCD bias level appears to have become unstable, resulting in sporadic images with either low or zero bias level. The other three CCDs {PC1, WF2, and WF3} appear to be unaffected and continue to operate properly. These darks are to supplement those in program 10748 to ensure sufficient dark frames for routine calibration.


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


10149 – GSACQ(2,3,2) failed,search radius limit exceeded on FGS 3 @058/1421z

GSACQ(2,3,2) at 058/14:17:55 failed due to Search Radius Limit Exceeded on FGS 3 at 14:21:09. One 486 status buffer message A05 (FGS Coarse Track failed- Search Radius Limit exceeded) was received. OBAD with maneuver prior to GSACQ had total RSS attitude error correction of 10.63 arcseconds, within the search radius. OBAD after failure had total RSS attitude error of 14.54 arcseconds.

10150 – GSACQ(2,1,2) Fine Lock Backup on FGS 1,Scam Step Limit on FGS 2 @058/1852z

GSACQ(2,1,2) at 058/18:48:19 ended in fine lock backup on FGS 1 due to scan step limit exceeded on FGS 2 at 18:51:44.

10151 – REacq(1,2,2) failed to RGA control @059/0743z

The Reacq(1,2,2)scheduled at 059/07:36:30 – 07:43:16 failed to RGA control. There were no SRLEX or SSLEX flags. ESB 1805 (T2G Moving Target Detected) was received at 07:38:26. Observation affected: ACS 46 – 49, WFPC 54 OBAD #2: V1=5.08, V2=-18.64, V3=5.70, RSS=20.14 The map at 07:43:15 showed errors of V1=1.69, V2=2.69, V3=5.34, RSS=6.21.

10152 – GSacq(2,1) failed to RGA control @059/0926z

GSac(2,1,2) scheduled at 059/09:22:35 failed to RGA control. There were no SRLEX or SSLEX flags. Also there were no ESB messages. OBAD1 showed errors of V1=-1770.37, V2=-1940.68, V3=-547.82, RSS=2683.39. OBAD2 showed errors of V1=6.32, V2=-5.76, V3=-0.22, RSS=8.55. The Map at 09:29:50 showed errors of V1=1.74, V2=-0.82, V3=-6.43, RSS=6.71



                        SCHEDULED      SUCCESSFUL      FAILURE TIMES
FGS GSacq               08                    06                @058/1421z 
(HSTAR 10149)
FGS REacq               07                    06                @059/0743z 
(HSTAR 10151)
OBAD with Maneuver  30                    30


SpaceRef staff editor.