Daily Report #4659

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT*** #4659

PERIOD COVERED: 5am July 23 - 5am July 24, 2008 (DOY
205/0900z-206/0900z)

OBSERVATIONS SCHEDULED

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 11321

NICMOS Cycle 16 Flats Stability

This calibration proposal is the Cycle 16 NICMOS flat field monitor
program. A series of camera 1, 2, & 3 flat fields will be obtained to
monitor the health of the cameras.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA Calibration - CR Persistence Part 6

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 i mages. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.

NIC2 11157

NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the
Stellar Mass Spectrum

Association of planetary systems with dusty debris disks is now quite
secure, and advances in our understanding of planet formation and
evolution can be achieved by the identification and characterization
of an ensemble of debris disks orbiting a range of central stars with
different masses and ages. Imaging debris disks in starlight scattered
by dust grains remains technically challenging so that only about a
dozen systems have thus far been imaged. A further advance in this
field needs an increased number of imaged debris disks. However, the
technical challenge of such observations, even with the superb
combination of HST and NICMOS, requires the best targets. Recent HST
imaging investigations of debris disks were sample-limited not limited
by the technology used. We performed a search for debris disks from a
IRAS/Hipparcos cross correlation which involved an exhaustive
background contamination check to weed out false excess stars. Out of
~140 identified debris disks, we selected 22 best targets in terms of
dust optical depth and disk angular size. Our target sample represents
the best currently available target set in terms of both disk
brightness and resolvability. For example, our targets have higher
dust optical depth, in general, than newly identified Spitzer disks.
Also, our targets cover a wider range of central star ages and masses
than previous debris disk surveys. This will help us to investigate
planetary system formation and evolution across the stellar mass
spectrum. The technical feasibility of this program in two-gyro mode
guiding has been proven with on-orbit calibration and science
observations during HST cycles 13, 14, and 15.

NIC3 11107

Imaging of Local Lyman Break Galaxy Analogs: New Clues to Galaxy
Formation in the Early Universe

We have used the ultraviolet all-sky imaging survey currently being
conducted by the Galaxy Evolution Explorer {GALEX} to identify for the
first time a rare population of low-redshift starbursts with
properties remarkably similar to high-redshift Lyman Break Galaxies
{LBGs}. These "compact UV luminous galaxies" {UVLGs} resemble LBGs in
terms of size, SFR, surface brightness, mass, metallicity, kinematics,
dust, and color. The UVLG sample offers the unique opportunity of
investigating some very important properties of LBGs that have
remained virtually inaccessible at high redshift: their morphology and
the mechanism that drives their star formation. Therefore, in Cycle 15
we have imaged 7 UVLGs using ACS in order to 1} characterize their
morphology and look for signs of interactions and mergers, and 2}
probe their star formation histories over a variety of timescales. The
images show a striking trend of small- scale mergers turning large
amounts of gas into vigorous starbursts {a process referred to as
dissipational or "wet" merging}. Here, we propose to complete our
sample of 31 LBG analogs using the ACS/SBC F150LP {FUV} and WFPC2
F606W {R} filters in order to create a statistical sample to study the
mechanism that triggers star formation in UVLGs and its implications
for the nature of LBGs. Specifically, we will 1} study the trend
between galaxy merging and SFR in UVLGs, 2} artificially redshift the
FUV images to z=1-4 and compare morphologies with those in similarly
sized samples of LBGs at the same rest-frame wavelengths in e.g.
GOODS, UDF, and COSMOS, 3} determine the presence and morphology of
significant stellar mass in "pre-burst" stars, and 4} study their
immediate environment. Together with our Spitzer {IRAC+MIPS}, GALEX,
SDSS and radio data, the HST observations will form a unique union of
data that may for the first time shed light on how the earliest major
episodes of star formation in high redshift galaxies came about. This
proposal was adapted from an ACS HRC+WFC proposal to meet the new
Cycle 16 observing constraints, and can be carried out using the
ACS/SBC and WFPC2 without compromising our original science goals.

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 11544

The Dynamical Legacy of Star Formation

We propose to use WFPC2 to conduct a wide-field imaging survey of the
young cluster IC348. This program, in combination with archival HST
observations, will allow us to measure precise proper motions for
individual cluster members, characterizing the intra-cluster velocity
dispersion and directly studying the dynamical signatures of star
formation and early cluster evolution. Our projected astrometric
precision (~1 mas in each epoch) will allow us to calculate individual
stellar velocities to unprecedented precision (0.5 mas/yr; 1 km/s)
and directly relate these velocities to observed spatial substructure
within the cluster. This survey will also allow us to probe
small-scale star formation physics by searching for high-velocity
stars ejected from decaying multiple systems, expanding our knowledge
of multiplicity in dense environments, and identifying new substellar
and planetary-mass cluster members based on kinematic membership
tests.

WFPC2/NIC2 11173

Completing an Accurate Map of M31 Microlensing

The halo microlensing masses detected in the MACHO survey (claimed to
compose about 20% of the Galaxy's mass) represent a major enigma in
astrophysics, one that must be effectively cross-examined by an
independent test. We have completed a large, densely-sampled survey of
M31 that can reveal in another galaxy such a halo microlensing signal
if it exists. In a previous HST/ACS+WFPC2 program (GO 10273, Cycle 13,
16 orbits) we were able to learn considerably more about a subsample
of these M31 microlensing events. We were pleased to find that in most
cases we could isolate the source star for each event, find its
baseline flux and colors (essential for ruling out classes of
confusing variable stars), test for misidentification of background
supernovae, and measure the Einstein parameters, which constrain the
range of most likely lens mass. (These Cycle 13 results are published
in The Astrophysical Journal Letters.) We propose to finish the job,
taking a similar series of exposures to more than double the sample of
well-constrained microlensing events, which together with the larger
ground-based sample for which we are completing our analyses will
provide 20-30 M31 bona fide microlensing events observed by HST. This
will be done via a series of targeted PC exposures, meant to maximize
the number of candidates studied, one (or two) at a time. A sample of
this size and quality should be sufficient to settle the issue of a
significant contribution to the halos of galaxies by stellar-mass
lenses. Furthermore, if there is a surplus of such microlensing events
above what might be expected from stars alone, the higher quality of
information will allow us to more accurately describe the spatial
distribution of these lenses. We will also complete several unique
studies of M31 stellar populations, both in support of the
microlensing measurement and in their own right.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

#11406 GSACQ(2,3,2) fine lock backup on FGS2 during LOS
@205/11:59:26z

QF3STOPF and QSTOP flags were set on FGS 3. Post acquisition
Observations affected: ACS #3, Proposal #11107; and NICMOS #47,
Proposal #08795.

#11408 GSAcq(2,3,2) failed to RGA Hold (Gyro Control) @205/18:53:30z
due to a Search Radius Limit Exceeded Error on FGS-2.

Also received "T2G OPEN LOOP TIMEOUT" and "TxG FHST SANITY CHECK
FAILED" ESB errors. Observations affected: WFPC #91-94, Proposal
ID#11173.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

***************************** SCHEDULED*** SUCCESSFUL
FGS GSacq********************** 14************ 13
FGS REacq*********************** 0************ 0
OBAD with Maneuver************* 28************ 26

SIGNIFICANT EVENTS: (None)