NASA Hubble Space Telescope Daily Status Report #4435

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.

HUBBLE SPACE TELESCOPE DAILY REPORT #4435

– Continuing to collect World Class Science

PERIOD COVERED: UT August 27, 2007 (DOY 239)

OBSERVATIONS SCHEDULED

WFPC2 10599

Multi-color imaging of two 1 Gyr old debris disks within 20 pc of the Sun: Astrophysical mirrors of our Kuiper Belt

We report the first scattered light detections of two debris disk around an F star and a K star using optical coronagraphy and the Hubble Space Telescope. With ages ~1 Gyr, these are the oldest debris disks thus far seen in the optical. We propose deep, multi-roll angle coronagraphic imaging with HST ACS and NICMOS to confirm and characterize the disks in terms of structure and composition. The disks appear to have belt-like morphology that is consistent with the existence of planetary companions or other perturbing bodies. Since these disks are close to our Kuiper Belt in an evolutionary context, detailed understanding of their mass, structure and composition will provide a fresh perspective for inferring the history and properties of our own trans-Neptunian region.

WFPC2 11024

WFPC2 CYCLE 15 INTERNAL MONITOR

This calibration proposal is the Cycle 15 routine internal monitor for WFPC2, to be run weekly to monitor the health of the cameras. A variety of internal exposures are obtained in order to provide a monitor of the integrity of the CCD camera electronics in both bays {both gain 7 and gain 15 — to test stability of gains and bias levels}, a test for quantum efficiency in the CCDs, and a monitor for possible buildup of contaminants on the CCD windows. These also provide raw data for generating annual super-bias reference files for the calibration pipeline.

FGS 11018

Long Term Stability of FGS1r in Position Mode

It is known from our experience with FGS3, and later with FGS1r, that an FGS on orbit experiences long term evolution, presumably due to disorption of water from the instrument’s graphite epoxy composites. This manifests primarily as a change in the plate scale and secondarily as a change in the geometric distortions. These effects are well modeled by adjustments to the rhoA and kA parameters which are used to transform the star selector servo angles into FGS {x, y} detector space coordinates. By observing the relative positions of selected stars in a standard cluster at a fixed telescope pointing and orientation, the evolution of rhoA and kA can be monitored and calibrated to preserve the astrometric performance of FGS1r.

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.

WFPC2 11196

An Ultraviolet Survey of Luminous Infrared Galaxies in the Local Universe

At luminosities above 10^11.4 L_sun, the space density of far-infrared selected galaxies exceeds that of optically selected galaxies. These Luminous Infrared Galaxies {LIRGs} are primarily interacting or merging disk galaxies undergoing starbursts and creating/fueling central AGN. We propose far {ACS/SBC/F140LP} and near {WFPC2/PC/F218W} UV imaging of a sample of 27 galaxies drawn from the complete IRAS Revised Bright Galaxy Sample {RBGS} LIRGs sample and known, from our Cycle 14 B and I-band ACS imaging observations, to have significant numbers of bright {23 < B < 21 mag} star clusters in the central 30 arcsec. The HST UV data will be combined with previously obtained HST, Spitzer, and GALEX images to {i} calculate the ages of the clusters as function of merger stage, {ii} measure the amount of UV light in massive star clusters relative to diffuse regions of star formation, {iii} assess the feasibility of using the UV slope to predict the far- IR luminosity {and thus the star formation rate} both among and within IR-luminous galaxies, and {iv} provide a much needed catalog of rest-frame UV morphologies for comparison with rest-frame UV images of high-z LIRGs and Lyman Break Galaxies. These observations will achieve the resolution required to perform both detailed photometry of compact structures and spatial correlations between UV and redder wavelengths for a physical interpretation our IRX-Beta results. The HST UV data, combined with the HST ACS, Spitzer, Chandra, and GALEX observations of this sample, will result in the most comprehensive study of luminous starburst galaxies to date.

WFPC2 11023

WFPC2 CYCLE 15 Standard Darks – part 1

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 11030

WFPC2 WF4 Temperature Reduction #3

In the fall of 2005, a serious anomaly was found in images from the WF4 CCD in WFPC2. The WF4 CCD bias level appeared to have become unstable, resulting in sporadic images with either low or zero bias level. The severity and frequency of the problem was rapidly increasing, making it possible that WF4 would soon become unusable if no work-around were found. Examination of bias levels during periods with frequent WFPC2 images showed low and zero bias episodes every 4 to 6 hours. This periodicity is driven by cycling of the WFPC2 Replacement Heater, with the bias anomalies occurring at the temperature peaks. The other three CCDs {PC1, WF2, and WF3} appear to be unaffected and continue to operate properly. Lowering the Replacement Heater temperature set points by a few degrees C effectively eliminates the WF4 anomaly. On 9 January 2006, the upper set point of the WFPC2 Replacement Heater was reduced from 14.9C to 12.2C. On 20 February 2006, the upper set point was reduced from 12.2C to 11.3C, and the lower set point was reduced from 10.9C to 10.0C. These changes restored the WF4 CCD bias level; however, the bias level has begun to trend downwards again, mimicking its behavior in late 2004 and early 2005. A third temperature reduction is planned for March 2007. We will reduce the upper set point of the heater from 11.3C to 10.4C and the lower set point from 10.0C to 9.1C. The observations described in this proposal will test the performance of WFPC2 before and after this temperature reduction. Additional temperature reductions may be needed in the future, depending on the performance of WF4. Orbits: internal 26, external 1.

WFPC2 11033

Full Moon Earth Flats Closeout

Flat field exposures will be obtained by observing the moonlit Earth with the broadband WFPC2 filters F606W and F814W, which saturate in the minimum exposure time on the sunlit Earth. These observations will be used to improve the flats currently in the pipeline and are part of the WFPC2 closeout operations. Because CTE effects are large for star flats and small for full field illumination, Earth flats are the superior technique.

WFPC2 11113

Binaries in the Kuiper Belt: Probes of Solar System Formation and Evolution

The discovery of binaries in the Kuiper Belt and related small body populations is powering a revolutionary step forward in the study of this remote region. Three quarters of the known binaries in the Kuiper Belt have been discovered with HST, most by our snapshot surveys. The statistics derived from this work are beginning to yield surprising and unexpected results. We have found a strong concentration of binaries among low-inclination Classicals, a possible size cutoff to binaries among the Centaurs, an apparent preference for nearly equal mass binaries, and a strong increase in the number of binaries at small separations. We propose to continue this successful program in Cycle 16; we expect to discover at least 13 new binary systems, targeted to subgroups where these discoveries can have the greatest impact.

WFPC2 11156

Monitoring Active Atmospheres on Uranus and Neptune

We propose Snapshot observations of Uranus and Neptune to monitor changes in their atmospheres on time scales of weeks and months. Uranus equinox is only months away, in December 2007. Hubble Space Telescope observations during the past several years {Hammel et al. 2005, Icarus 175, 284 and references therein} have revealed strongly wavelength-dependent latitudinal structure, the presence of numerous visible-wavelength cloud features in the northern hemisphere, at least one very long-lived discrete cloud in the southern hemisphere, and in 2006 the first dark spot ever seen on Uranus. Long-term ground-based observations {Lockwood and Jerzekiewicz, 2006, Icarus 180, 442; Hammel and Lockwood 2007, Icarus 186, 291} reveal seasonal brightness changes whose origins are not well understood. Recent near-IR images of Neptune obtained using adaptive optics on the Keck Telescope, together with HST observations {Sromovsky et al. 2003, Icarus 163, 256 and references therein} which include previous Snapshot programs {GO 8634, 10170, 10534} show a general increase in activity at south temperate latitudes until 2004, when Neptune returned to a rather Voyager-like appearance. Further Snapshot observations of these two dynamic planets will elucidate the nature of long-term changes in their zonal atmospheric bands and clarify the processes of formation, evolution, and dissipation of discrete albedo features.

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.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10961 – REacq(2,1,1) results in fine lock backup (2,0,2) using FGS-2

The REacq(2,1,1) scheduled at 239/19:37:08 – 19:45:12 resulted in fine lock backup (2,0,2) using FGS-2 due to (QF1STOPF) stop flag indication on FGS-1. Pre-acquisition OBADs showed (RSS) attitude correction values of 868.94 and 7.06 arcseconds. Post-acquisition OBAD/MAP had (RSS) value of 15.80 arcseconds.

10962 – Coarse Mode Angle Check Failure

At AOS (240/07:22:01) observed 486 ESB “A0C”, Coarse Mode Angle Check Failed. During the LOS from 240/05:23:04 – 07:22:01 there was a ReAcq @ 05:55:07 and after slewing to a new attitude a GSAcq @ 06:51:52. The #44 command (-205.746) has not changed since the GSAcq @ 04:18:46. Currently awaiting an engineering dump for further analysis.

At AOS OBAD #2: V1 -5.68, V2 -6.75, V3 -6.96, RSS 11.24

At AOS (240/09:04:16) received 486 ESB “A0C”, Coarse Mode Angle Check Failed. REAcq occurred at 08:24:13 and the #44 command has not changed. No other flags were noted.

OBAD #2 V1 -8.77, V2 -6.00, V3 -8.99, RSS 13.92

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                 SCHEDULED      SUCCESSFUL 

FGS GSacq          08              08 
FGS REacq          06              04 
OBAD with Maneuver 24              24 

SIGNIFICANT EVENTS: (None)