NASA Hubble Space Telescope Daily Report # 3667

Status Report From: Space Telescope Science Institute
Posted: Thursday, August 5, 2004

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science




ACS/HRC 10050

ACS Earth Flats

High signal 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 used by the pipeline and will provide a comparison with flats derived via other techniques: L-flats from stellar observations, sky flats from stacked GO observations, and internal flats using the calibration lamps. Weekly coronagraphic monitoring is required to assess the changing position of the spots.


CCD Daily Monitor

This program consists of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. This programme will be executed once a day for the entire lifetime of ACS.

ACS/WFC 10120

The Formation Histories and Dynamical Roles of X-ray Binaries in Globular Clusters

Close binaries are fundamental to the dynamical stability and evolution of globular clusters, but large populations have been extremely difficult to identify. Chandra X-ray images provide a revolutionary resource, revealing a few to dozens of low-luminosity X-ray sources in every cluster deeply examined; our own Chandra programs uniformly study these ubiquitous X-ray sources {close binaries and their progeny} in 11 clusters. However, definitive understanding of the nature of the various X-ray subpopulations requires the identification of optical counterparts, and HST is the demonstrated key in these crowded environments. We thus propose a proven, efficient, and uniform, HST multicolor imaging program for optical identifications in 6 of our clusters with Chandra data on-hand, but which lack adequate optical images in the HST archive. The proposed ACS images will permit statistical classifications into the various subtypes: CVs, qLMXBs, BY Dra's/RS CVn's {and MSPs}. A unique aspect of our program is that our clusters span a range of physical properties such as central concentration, cluster size, and mass--essential ingredients in the formation, evolution, and dynamical roles of cluster binaries. Exploiting this range of properties, we have identified a relation that provides the first compelling link between the number of X-ray sources and the predicted stellar encounter frequency in globular cluster cores. But further progress in understanding the details implicit in this relationship {e.g., whether CVs and qLMXBs formed primarily via stellar encounters, while BY Dra's/RS CVn's are mainly primordial binaries} demands uniform optical identifications for multiple clusters, spanning the full range physical properties.

ACS/WFC 10210

Groups of Dwarf Galaxies: Pools of Mostly Dark Matter?

Within 5 Mpc, there are 6 groups with well-known luminous galaxies but there also appears to be a comparable number of groups containing only dwarfs. If these dwarf entities are truly bound then M/L values are an order of magnitude higher than values found for groups with luminous spiral galaxies. There are theoretical reasons to anticipate that low mass halos may frequently be mostly dark. The dynamical influence of low mass halos is negligible in familiar groups with luminous members. By contrast, a study of the dynamics of `groups of dwarfs' may provide direct evidence of the existence of dark matter potential wells with few baryons. The goal of the present study is to gather detailed information on the 3-D distribution of dwarf galaxies suspected to lie within 7 groups of dwarfs within 5 Mpc. Distances with 7% relative accuracy can be measured with the Tip of the Giant Branch method with ACS and integrations within 1 orbit per target.

ACS/WFC 9727

Exploration of the SN Ia Hubble Diagram at z > 1.2

In the spirit of a Treasury proposal, we propose to organize, and deliver to the astronomical community, non-proprietary follow-up observations of ~10 Type Ia supernovae at 1<z<1.7 that are expected to be discovered in a Cycle 12 Treasury proposal. Together with the currently available sample, this would provide a Hubble diagram with over 20 SNe Ia in this redshift range, where it is possible to test the current cosmological model in the epoch of deceleration: If z ~ 0.5 SNe Ia are fainter due to evolution rather than an accelerating expansion, they should continue to get fainter at even higher redshifts. This size sample will show trends and outliers, and permit a more rigorous treatment of the asymmetric amplification distribution from gravitational lensing. This is a key redshift range for the studies of dark energy that will be done with future surveys {and future instruments now being designed}; this dataset will lay the ground-work for these studies by establishing the simple properties of the supernovae in this redshift range, including magnitudes, colors, and timescales. If considered more appropriate, this proposal could be treated as a part of a Treasury or Director's Discretionary program, since the data would be available to everybody immediately, and we would welcome others who would want to work with us on it.

FGS 10113

Trigonometric Calibration of the Period- Luminosity Relations for Fundamental and First-Overtone Galactic Cepheids

Cepheids are the primary distance indicators for the extragalactic distance scale and the Hubble constant. The Hubble Constant Key Project set the zero-point for their Cepheid distance scale by adopting a distance to the LMC, averaged over a variety of techniques. However, different methods give an LMC distance modulus ranging from 18.1 to 18.8, and the uncertainty in the Cepheid zero-point is now the largest contributor to the error budget for H_0. Moreover, the low metallicity of the LMC raises additional concerns, since the PL relation probably depends on metallicity. The zero-point can be determined from Hipparcos parallaxes of Galactic Cepheids out to several hundred parsecs, but with a typical parallax error of 0.5-1 mas, the Hipparcos error bars are uncomfortably large for this demanding application. By contrast, HST's FGS1R interferometer can achieve astrometric accuracy of 0.2 mas. We propose to use FGS1R to determine trigonometric parallaxes for a sample of 9 nearby Cepheids, including both fundamental {F} and first-overtone {FO} pulsators. We show that the improvement in the PL relations for F and FO Cepheids will be dramatic. We will determine the PL slopes from our nearby solar- metallicity sample alone, without recourse to nearby galaxies and the issue of [Fe/H] dependence. The zero-point will be determined robustly to about 0.05 mag, based on accurate, purely geometrical measurements. All of this can be achieved in the next few years with HST, without having to wait for the technically demanding and risky SIM and GAIA missions well into the next decade.

NIC/NIC3 10226

The NICMOS Grism Parallel Survey

We propose to continue managing the NICMOS pure parallel program. Based on our experience, we are well prepared to make optimal use of the parallel opportunities. The improved sensitivity and efficiency of our observations will substantially increase the number of line-emitting galaxies detected. As our previous work has demonstrated, the most frequently detected line is Halpha at 0.7<z<1.9, which provides an excellent measure of current star formation rate. We will also detect star-forming and active galaxies in other redshift ranges using other emission lines. The grism observations will produce by far the best available Halpha luminosity functions over the crucial--but poorly observed--redshift range where galaxies appear to have assembled most of their stellar mass. This key process of galaxy evolution needs to be studied with IR data; we found that observations at shorter wavelengths appear to have missed a large fraction of the star-formation in galaxies, due to dust reddening. We will also obtain deep F110W and F160W images, to examine the space densities and morphologies of faint red galaxies. In addition to carrying out the public parallels, we will make the fully reduced and calibrated images and spectra available on-line, with some ground-based data for the deepest parallel fields included.

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.

STIS/CCD 10018

CCD Dark Monitor-Part 2

Monitor the darks for the STIS CCD.

STIS/CCD 10020

CCD Bias Monitor - Part 2

Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1, and 1x1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.

STIS/CCD 10030

STIS/CCD Spectroscopic Sensitivity Monitor for Cycle 12

Monitor sensitivity of each CCD grating mode to detect any change due to contamination or other causes.

STIS/MA1 10034

Cycle 12 MAMA Dark Monitor

This test performs the routine monitoring of the MAMA detector dark noise. This proposal will provide the primary means of checking on health of the MAMA detectors systems through frequent monitoring of the background count rate. The purpose is to look for evidence of change in dark indicative of detector problem developing.

WFPC2 10071

WFPC2 CYCLE 12 Supplemental Darks Part 3/3

This dark calibration program obtains 3 dark frames every day to provide data for monitoring and characterizing the evolution of hot pixels.


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

HSTAR 9500: STIS Mechanism Power (OMBMC5V) flagged OOL red low (6.2943-5 Volts) @ 216/15:57:22Z. In FN format, STIS was not in use. Under investigation.

HSTAR 9501: STIS Suspend @ 216/16:38:21. Received Status Buffer message STIS 738 and STIS 734. Under investigation.

HSTAR 9503: STIS Zone 3B Temperature (OTCZ3BT) began flagging OOL intermittently @ 217/06:54:32Z, reaching a low value of 16.6429 ?C. Lower limit is 17.0 ?C. Under investigation.


  • 17238-0 Real Time Map @ 216/0929z
  • 17239-0 Dump STIS Memory after Suspend @ 216/1818z


  • 0900-1 COMMAND PROBLEM @ 216/20:32:19z
  • 0924-0 HSTAR Documentation for Guide Star Acq Failure/Loss of Lock @ 216/08:57:58z (Ref HSTAR # 9499)

                       SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq            08                       08
FGS REacq            05                       04             216/08:57:58z 
(Ref HSTAR # 9499)
FHST Update          10                       10


STIS suspended @ 216/16:38:21Z following receipt of two Status Buffer messages (STIS 738 and STIS 734). See HSTARs 9501. Prior to the suspend, STIS was in Operate with Low Voltage on. MEB/SES + 5 Volt Power Supply (OMBMC5V) was flagging OOL low (6.29425-5 Volts) coming out of ZOE @ 216/15:57Z. See HSTAR 9500. Subsequent extraction of SSR engineering data indicated there was a sudden drop from the nominal operating Voltage @ 216/15:55:21Z. No STIS SPC was taking place around the initial OOL or the suspend. Successfully executed STIS memory dump after Suspend @ 216/18:18Z (OR 17239 with ROP NS-10).

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