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 i
mages. 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
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
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)