Status Report

NASA Hubble Space Telescope Daily Report #5130

By SpaceRef Editor
July 8, 2010
Filed under , ,


Continuing to Collect World Class Science

PERIOD COVERED: 5am July 1 – 5am July 2, 2010 (DOY 182/09:00z-183/09:00z)


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

HSTARS: (None)



FGS GSAcq 4 4
FGS REAcq 12 12
OBAD with Maneuver 4 4



ACS/WFC3 11586

Exceptional Galactic Halo Globular Clusters and the Second Parameter

We propose to obtain deep ACS-WFC images of six globular clusters (five of which have no previous HST photometry) that reside in the Galactic halo, where the second parameter effect is most pronounced. These globular clusters are among the least studied in the Galaxy and yet, from the perspective of the second parameter phenomenon, the most intriguing.

With the best available CMDs only reaching the vicinity of the main sequence turn off at present, the unique sensitivity and resolution of ACS-WFC will yield ages of unprecedented precision for these clusters. These data will provide us with new insight into the stellar populations present in the outer Galactic halo and the nature of the second parameter. The second parameter plays a critical role in our understanding of the formation and evolution of the Galaxy and the proposed observations will shed new light on this problem and these exceptional clusters.


Probing the Interior of SN1006

The remnant of SN 1006 is unique among all supernova remnants in having 3 identified background UV sources that can be used to probe cold, otherwise unseen ejecta within the remnant shell. We propose high-resolution spectra from COS to obtain spectra of all three of these. The brightest of these, the Schweizer-Middleditch star (the only one with extensive previous high-quality UV spectra) shows Si II absorption with an extremely unusual asymmetric profile with a sharp edge on the red end, indicating the velocity of material just entering the reverse shock. Our new spectrum can be compared with STIS observations from 1999 to measure definitively the velocity change as the reverse shock eats its way into ever-more- slowly-expanding ejecta. One may well ask, however, if this profile is truly representative, and we seek to answer that with a spectrum of a background quasar at a similar distance of the SM star from the projected center, but in a different direction. And by investigating the detailed structure of these two sources and a second quasar, we can probe small-scale structure in the ejecta. No object other than SN1006 offers a similar opportunity to probe the distribution of ejecta within the remnant of a Type Ia supernova.

S/C 12046

COS FUV DCE Memory Dump

Whenever the FUV detector high voltage is on, count rate and current draw information is collected, monitored, and saved to DCE memory. Every 10 msec the detector samples the currents from the HV power supplies (HVIA, HVIB) and the AUX power supply (AUXI). The last 1000 samples are saved in memory, along with a histogram of the number of occurrences of each current value.

In the case of a HV transient (known as a “crackle” on FUSE), where one of these currents exceeds a preset threshold for a persistence time, the HV will shut down, and the DCE memory will be dumped and examined as part of the recovery procedure. However, if the current exceeds the threshold for less than the persistence time (a “mini-crackle” in FUSE parlance), there is no way to know without dumping DCE memory. By dumping and examining the histograms regularly, we will be able to monitor any changes in the rate of “mini-crackles” and thus learn something about the state of the detector.

STIS/CC 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CC 11847

CCD Bias Monitor-Part 2

Monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.

STIS/CCD/MA1/MA2 11839

The Cycles of Alpha Centauri

This is the HST part of a joint Chandra/HST observing program. The objective of the HST part is to obtain new UV spectra of both components of the Alpha Centauri binary: the primary (“Alpha Cen A”) is a near twin of the Sun, while the companion (“B”) is an early K dwarf, slightly less massive, smaller and less luminous than the Sun. The orbital period is 80 yr, and the two stars currently are separated by about 8″. The Alpha Cen system has been the subject of long term coronal X-ray monitoring by four successive generations of space observatories, and extensive UV measurements were obtained periodically during the IUE era, from the late 1970’s to late 1990’s. The present program will obtain new STIS echelle spectra of both stars, which each were observed in selected wavelength windows by GHRS in the mid-1990’s, and Alpha Cen A later by STIS in an extensive high-res program in 1999, although B unfortunately never was recorded by STIS.

WFC3/IR 11631

Binary Brown Dwarfs and the L/T Transition

Brown dwarfs traverse spectral types M, L and T as their atmospheric structure evolves and they cool into oblivion. This SNAPSHOT program will obtain WFC3-IR images of 45 nearby late-L and early-T dwarfs to investigate the nature of the L/T transition. Recent analyses have suggested that a substantial proportion of late-L and early-T dwarfs are binaries, comprised of an L dwarf primary and T dwarf secondary. WFC3-IR observations will let us quantify this suggestion by expanding coverage to a much larger sample, and permitting comparison of the L/T binary fraction against ?normal? ultracool dwarfs. Only eight L/T binaries are currently known, including several that are poorly resolved: we anticipate at least doubling the number of resolved systems. The photometric characteristics of additional resolved systems will be crucial to constraining theoretical models of these late-type ultracool dwarfs. Finally, our data will also be eminently suited to searching for extremely low luminosity companions, potentially even reaching the Y dwarf regime.

WFC3/IR 11648

WFC3 Spectroscopy of an X-ray Luminous Galaxy Cluster at z>2

We propose to obtain deep WFC3+G141 grism observations to spectroscopically confirm a remarkable z>2 cluster of galaxy candidate. Over a 1000 arcmin^2 field imaged with Spitzer’s IRAC we have discovered a compact (<30ÕÕ diameter) concentration of extremely red galaxies with a factor of >40 overdensity over the adjacent field. Among these galaxies for which we can derive meaningful photometric redshifts, 17 are consistent with zphot=2-2.5, making it very likely that the concentration is a real cluster at such high redshift. This is further supported by a 3.5 sigma detection of extended X-Ray emission on XMM-Newton data, by a likely color magnitude sequence of red galaxies, and by the presence of a giant galaxy consistent with a BCG at the cluster redshift. The general faintness of the red galaxies in all optical bands and their high redshifts prevent confirmation of this cluster with ordinary optical spectroscopy. The WFC3 camera with G141 grism provides the only way to confirm this record high-z cluster and measure its redshift from spectral breaks typical of old stellar populations. Our deep integrations will reveal redshifts for at least 19 ultra-red galaxies in the area and of a similar number of bluer galaxies at the cluster redshift. Knowledge of the cluster redshift based on the HST spectra will allow us to reach important scientific aims: find the most distant Xray emitting evolved galaxy cluster, determine membership of the other galaxies from photometric SED analysis, study their stellar population properties, characterize the color-magnitude relation with constraints on the formation redshift. The proposed observations will establish a first z>2 benchmark for cluster field comparisons of galaxy formation at this highest redshift and will firmly establish the progenitors of local rich Abell clusters.

WFC3/IR 11915

IR Internal Flat Fields

This program is the same as 11433 (SMOV) and depends on the completion of the IR initial alignment (Program 11425). This version contains three instances of 37 internal orbits: to be scheduled early, middle, and near the end of Cycle 17, in order to use the entire 110-orbit allocation.

In this test, we will study the stability and structure of the IR channel flat field images through all filter elements in the WFC3-IR channel. Flats will be monitored, i.e. to capture any temporal trends in the flat fields and delta flats produced. High signal observations will provide a map of the pixel-to-pixel flat field structure, as well as identify the positions of any dust particles.

WFC3/IR/S/C 11929

IR Dark Current Monitor

Analyses of ground test data showed that dark current signals are more reliably removed from science data using darks taken with the same exposure sequences as the science data, than with a single dark current image scaled by desired exposure time. Therefore, dark current images must be collected using all sample sequences that will be used in science observations. These observations will be used to monitor changes in the dark current of the WFC3-IR channel on a day-to-day basis, and to build calibration dark current ramps for each of the sample sequences to be used by Gos in Cycle 17. For each sample sequence/array size combination, a median ramp will be created and delivered to the calibration database system (CDBS).

WFC3/UVIS 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set of full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K subarray biases are acquired at less frequent intervals throughout the cycle to support subarray science observations. The internals from this proposal, along with those from the anneal procedure (Proposal 11909), will be used to generate the necessary superbias and superdark reference files for the calibration pipeline (CDBS).

WFC3/UVIS 11908

Cycle 17: UVIS Bowtie Monitor

Ground testing revealed an intermittent hysteresis type effect in the UVIS detector (both CCDs) at the level of ~1%, lasting hours to days. Initially found via an unexpected bowtie-shaped feature in flatfield ratios, subsequent lab tests on similar e2v devices have since shown that it is also present as simply an overall offset across the entire CCD, i.e., a QE offset without any discernable pattern. These lab tests have further revealed that overexposing the detector to count levels several times full well fills the traps and effectively neutralizes the bowtie. Each visit in this proposal acquires a set of three 3×3 binned internal flatfields: the first unsaturated image will be used to detect any bowtie, the second, highly exposed image will neutralize the bowtie if it is present, and the final image will allow for verification that the bowtie is gone.

SpaceRef staff editor.