Daily Report #4689

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4689

PERIOD COVERED: 5am September 4 - 5am September 5, 2008 (DOY
248/0900z-249/0900z)

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 11820

NICMOS Post-SAA Calibration - CR Persistence Part 7

Internals for CR persistence

NIC2 11548

NICMOS Imaging of Protostars in the Orion A Cloud: The Role of Environment
in Star Formation

We propose NICMOS observations of a sample of 252 protostars identified in
the Orion A cloud with the Spitzer Space Telescope. These observations will
image the scattered light escaping the protostellar envelopes, providing
information on the shapes of outflow cavities, the inclinations of the
protostars, and the overall morphologies of the envelopes. In addition, we
ask for Spitzer time to obtain 55-95 micron spectra of 75 of the protostars.
Combining these new data with existing 3.6 to 70 micron photometry and
forthcoming 5-40 micron spectra measured with the Spitzer Space Telescope,
we will determine the physical properties of the protostars such as envelope
density, luminosity, infall rate, and outflow cavity opening angle. By
examining how these properties vary with stellar density (i.e. clusters vs
groups vs isolation) and the properties of the surrounding molecular cloud;
we can directly measure how the surrounding environment influences
protostellar evolution, and consequently, the formation of stars and
planetary systems. Ultimately, this data will guide the development of a
theory of protostellar evolution.

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 11201

Systemic and Internal motions of the Magellanic Clouds: Third Epoch Images

In Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields in the
Magellanic Clouds centered on background quasars. We used these data to
determine the proper motions of the LMC and SMC to better than 5% and 15%
respectively. These are by far the best determinations of the proper motions
of these two galaxies. The results have a number of unexpected implications
for the Milky Way-LMC-SMC system. The implied three-dimensional velocities
are larger than previously believed, and are not much less than the escape
velocity in a standard 10^12 solar mass Milky Way dark halo. Orbit
calculations suggest the Clouds may not be bound to the Milky Way or may
just be on their first passage, both of which would be unexpected in view of
traditional interpretations of the Magellanic Stream. Alternatively, the
Milky Way dark halo may be a factor of two more massive than previously
believed, which would be surprising in view of other observational
constraints. Also, the relative velocity between the LMC and SMC is larger
than expected, leaving open the possibility that the Clouds may not be bound
to each other. To further verify and refine our results we now request an
epoch of WFPC2/PC data for the fields centered on 40 quasars that have at
least one epoch of ACS imaging. We request execution in snapshot mode, as in
our previous programs, to ensure the most efficient use of HST resources. A
third epoch of data of these fields will provide crucial information to
verify that there are no residual systematic effects in our previous
measurements. More importantly, it will increase the time baseline from 2 to
5 yrs and will increase the number of fields with at least two epochs of
data. This will reduce our uncertainties correspondingly, so that we can
better address whether the Clouds are indeed bound to each other and to the
Milky Way. It will also allow us to constrain the internal motions of
various populations within the Clouds, and will allow us to determine a
distance to the LMC using rotational parallax.

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 11795

WFPC2 Cycle 16 UV Earth Flats

Monitor flat field stability. This proposal obtains sequences of earth
streak flats to improve the quality of pipeline flat fields for the WFPC2 UV
filter set. These Earth flats will complement the UV earth flat data
obtained during cycles 8-15.

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 11 11
FGS REacq 04 04
OBAD with Maneuver 30 30

SIGNIFICANT EVENTS: (None)