Daily Report #4660

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT*** #4660

PERIOD COVERED: 5am July 24 - 5am July 25, 2008 (DOY
206/0900z-207/0900z)

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

NIC3 11332

NICMOS Cycle 16 Time Dependent Flat Fields

This proposal obtains sequences of NICMOS narrow, medium and broad
band filter flat fields for camera 1. In cameras 2 and 3, parallel
observations will allow us to obtain high S/N flats for all spectral
elements.

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 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 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: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

******************************* SCHEDULED***** SUCCESSFUL

FGS GSacq*********************** 9******************* 9
FGS REacq*********************** 1******************* 1
OBAD with Maneuver******** **** 20***************** 20

SIGNIFICANT EVENTS: (None)