Status Report

NASA Hubble Space Telescope Daily Report #4398

By SpaceRef Editor
July 9, 2007
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NASA Hubble Space Telescope Daily Report  #4398

Notice: Due to the conversion of some ACS WFC or HRC observations into WFPC2, or NICMOS observations after the loss of ACS CCD science capability in January, there may be an occasional discrepancy between a proposal’s listed (and correct) instrument usage and the abstract that follows it.


– Continuing to collect World Class Science

PERIOD COVERED: UT July 05, 2007 (DOY 186)


ACS/SBC 10872

Lyman Continuum Emission in Galaxies at z=1.2

Lyman continuum photons produced in massive starbursts may have played a dominant role in the reionization of the Universe. Starbursts are important contributors to the ionizing metagalactic background at lower redshifts as well. However, their contribution to the background depends upon the fraction of ionizing radiation that escapes from the intrinsic opacity of galaxies below the Lyman limit. Current surveys suggest escape fractions of a few percent, up to 10%, with very few detections {as opposed to upper limits} having been reported. No detections have been reported in the epochs between z=0.1 and z=2. We propose to measure the fraction of escaping Lyman continuum radiation from 15 luminous z~1.2 galaxies in the GOODS fields. Using the tremendous sensitivity of the ACS Solar- blind Channel, we will reach AB=30 mag., allowing us to detect an escape fraction of 1%. We will correlate the amount of escaping radiation with the photometric and morphological properties of the galaxies. A non-detection in all sources would imply that QSOs provide the overwhelming majority of ionizing radiation at z=1.3, and it would strongly indicate that the properties of galaxies at higher redshift have to be significantly different for galaxies to dominate reionization. The deep FUV images will also be useful for extending the FUV study of other galaxies in the GOODS fields.

FGS 11212

Filling the Period Gap for Massive Binaries

The current census of binaries among the massive O-type stars is seriously incomplete for systems in the period range from years to millennia because the radial velocity variations are too small and the angular separations too close for easy detection. Here we propose to discover binaries in this observational gap through a Faint Guidance Sensor SNAP survey of relatively bright targets listed in the Galactic O Star Catalog. Our primary goal is to determine the binary frequency among those in the cluster/association, field, and runaway groups.  The results will help us assess the role of binaries in massive star formation and in the processes that lead to the ejection of massive stars from their natal clusters. The program will also lead to the identification of new, close binaries that will be targets of long term spectroscopic and high angular resolution observations to determine their masses and distances. The results will also be important for the interpretation of the spectra of suspected and newly identified binary and multiple systems.

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.

NIC3 11062

NICMOS non-linearity tests

This program incorporates a number of tests to analyze the count rate dependent non- linearity seen in NICMOS spectro-photometric observations. We will observe a field with stars of a range in luminosity in NGC3603 with NICMOS in NIC1: F090M, F110W, F140W, F160W NIC2: F110W, F160W, F187W, F205W, and F222M NIC3: F110W, F150W, F160W, F175W, and F222M. We will repeat the observations with flatfield lamp on, creating artificially high count-rates, allowing tests of NICMOS linearity as function of count rate. We first take exposures with the lamp off, then exposures with the lamp on, and repeat at the end with lamp off. Finally, we continue with taking darks during occultation. We will furthermore observe spectro-photometric standard P041C using the G096, G141, and G206 grisms in NIC3, and repeat the lamp off/on/off test to artificially create a high background.

WFPC2 11175

UV Imaging to Determine the Location of Residual Star Formation in Galaxies Recently Arrived on the Red Sequence

We have identified a sample of low-redshift {z = 0.04 – 0.10} galaxies that are candidates for recent arrival on the red sequence. They have red optical colors indicative of old stellar populations, but blue UV-optical colors that could indicate the presence of a small quantity of continuing or very recent star formation. However, their spectra lack the emission lines that characterize star-forming galaxies. We propose to use ACS/SBC to obtain high- resolution imaging of the UV flux in these galaxies, in order to determine the spatial distribution of the last episode of star formation. WFPC2 imaging will provide B, V, and I photometry to measure the main stellar light distribution of the galaxy for comparison with the UV imaging, as well as to measure color gradients and the distribution of interstellar dust. This detailed morphological information will allow us to investigate the hypothesis that these galaxies have recently stopped forming stars and to compare the observed distribution of the last star formation with predictions for several different mechanisms that may quench star formation in galaxies.

WFPC2 11178

Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries

The recent discovery of numerous transneptunian binaries {TNBs} opens a window into dynamical conditions in the protoplanetary disk where they formed as well as the history of subsequent events which sculpted the outer Solar System and emplaced them onto their present day heliocentric orbits. To date, at least 47 TNBs have been discovered, but only about a dozen have had their mutual orbits and separate colors determined, frustrating their use to investigate numerous important scientific questions. The current shortage of data especially cripples scientific investigations requiring statistical comparisons among the ensemble characteristics. We propose to obtain sufficient astrometry and photometry of 23 TNBs to compute their mutual orbits and system masses and to determine separate primary and secondary colors, roughly tripling the sample for which this information is known, as well as extending it to include systems of two near-equal size bodies. To make the most efficient possible use of HST, we will use a Monte Carlo technique to optimally schedule our observations.


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


#10882 GSacq(2,3,2) fails to RGA control.

Upon acquisition of signal at 187/05:46:34 vehicle was in RGA control. GSacq(2,3,2) scheduled at 05:17:14 failed to RGA control. 486 ESB message “A07” (“FGS Coarse Track failed – Time out waiting for Data Valid”) was received. No FGS flags were seen. OBAD prior to GSACQ at 05:12:54 had RSS error of 2.25 arcseconds.

#10883 GSacq(2,3,2) failed, Search Radius Limit exceeded on FGS 2. Upon acquisition of signal at 187/07:29:15 vehicle was in RGA control with FGS2 Search Radius Limit and Stop flags set. GSacq(2,3,2) scheduled at 06:57:57 failed with search radius limit exceeded on FGS 2.

The following 486 ESB messages were received:

06:56:35 ESB 1904 OBAD Too Many Angle Checks

07:03:58 ESB A05 message (FGS Coarse Track failed- search Radius Limit exceeded)

Post-acquisition OBAD/MAP at 07:48:44 had RSS error of 303.64 arcseconds. OBADs prior to GSACQ are not available.


                               SCHEDULED SUCCESSFUL 
FGS GSacq                       8                6 
FGS REacq                       3                3 
OBAD with Maneuver              23               22 



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