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 - Continuing to collect World Class Science

DAILY REPORT      # 4436

PERIOD COVERED: UT August 28, 2007 (DOY 240)

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 10915

ACS Nearby Galaxy Survey

Existing HST observations of nearby galaxies comprise a sparse and

highly non-uniform archive, making comprehensive comparative studies

among galaxies essentially impossible. We propose to secure HST's

lasting impact on the study of nearby galaxies by undertaking a

systematic, complete, and carefully crafted imaging survey of ALL

galaxies in the Local Universe outside the Local Group. The resulting

images will allow unprecedented measurements of: {1} the star formation

history {SFH} of a >100 Mpc^3 volume of the Universe with a time

resolution of Delta[log{t}]=0.25; {2} correlations between spatially

resolved SFHs and environment; {3} the structure and properties of thick

disks and stellar halos; and {4} the color distributions, sizes, and

specific frequencies of globular and disk clusters as a function of

galaxy mass and environment. To reach these goals, we will use a

combination of wide-field tiling and pointed deep imaging to obtain

uniform data on all 72 galaxies within a volume-limited sample extending

to ~3.5 Mpc, with an extension to the M81 group. For each galaxy, the

wide-field imaging will cover out to ~1.5 times the optical radius and

will reach photometric depths of at least 2 magnitudes below the tip of

the red giant branch throughout the limits of the survey volume. One

additional deep pointing per galaxy will reach SNR~10 for red clump

stars, sufficient to recover the ancient SFH from the color-magnitude

diagram. This proposal will produce photometric information for ~100

million stars {comparable to the number in the SDSS survey} and uniform

multi- color images of half a square degree of sky. The resulting

archive will establish the fundamental optical database for nearby

galaxies, in preparation for the shift of high- resolution imaging to

the near-infrared.

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 11218

Snapshot Survey for Planetary Nebulae in Globular Clusters of the Local

Group

Planetary nebulae {PNe} in globular clusters {GCs} raise a number of

interesting issues related to stellar and galactic evolution. The number

of PNe known in Milky Way GCs, 4, is surprisingly low if one assumes

that all stars pass through a PN stage. However, it is likely that the

remnants of stars now evolving in Galactic GCs leave the AGB so slowly

that any ejected nebula dissipates long before the star becomes hot

enough to ionize it. Thus there should not be ANY PNe in Milky Way

GCs--but there are four! It has been suggested that these PNe are the

result of mergers of binary stars within GCs, i.e., that they are

descendants of blue stragglers. The frequency of occurrence of PNe in

external galaxies poses more questions, because it shows a range of

almost an order of magnitude. I propose a Snapshot survey aimed at

discovering PNe in the GC systems of Local Group galaxies more distant

than the Magellanic Clouds. These clusters, some of which may be much

younger than their counterparts in the Milky Way, might contain many

more PNe than those of our own galaxy. I will use the standard technique

of emission-line and continuum imaging, which easily discloses PNe.

WFPC2 11289

SL2S: The Strong Lensing Legacy Survey

Recent systematic surveys of strong galaxy-galaxy lenses {CLASS, SLACS,

GOODS, etc.} are producing spectacular results for galaxy masses roughly

below a transition mass M~10^13 Mo. The observed lens properties and

their evolution up to z~0.2, consistent with numerical simulations, can

be described by isothermal elliptical potentials. In contrast, modeling

of giant arcs in X-ray luminous clusters {halo masses M >~10^13 Mo}

favors NFW mass profiles, suggesting that dark matter halos are not

significantly affected by baryon cooling. Until recently, lensing

surveys were neither deep nor extended enough to probe the intermediate

mass density regime, which is fundamental for understanding the assembly

of structures. The CFHT Legacy Survey now covers 125 square degrees, and

thus offers a large reservoir of strong lenses probing a large range of

mass densities up to z~1. We have extracted a list of 150 strong lenses

using the most recent CFHTLS data release via automated procedures.

Following our first SNAPSHOT proposal in cycle 15, we propose to

continue the Hubble follow-up targeting a larger list of 130 lensing

candidates. These are intermediate mass range candidates {between

galaxies and clusters} that are selected in the redshift range of 0.2-1

with no a priori X-ray selection. The HST resolution is necessary for

confirming the lensing candidates, accurate modeling of the lenses, and

probing the total mass concentration in galaxy groups up to z~1 with the

largest unbiased sample available to date.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary reports

of potential non-nominal performance that will be investigated.)

HSTARS:

10963 - GSAcq(1,2,1) results in Fine Lock Back-up (1,0,1)

           GSAcq (1,2,1) scheduled at 241/06:40:56 resulted in Fine Lock Back-up

           (1,0,1) using FGS 1.

           OBAD #1 RSS: 2125.80

           OBAD #2 RSS: 7.20

           OBAD MAP RSS:

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                       SCHEDULED      SUCCESSFUL

FGS GSacq               07                  07                       

FGS REacq               05                  05                                                   

OBAD with Maneuver 24                  24              

SIGNIFICANT EVENTS: (None)