Daily Rpt #4791

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT****** #4791

PERIOD COVERED: 5am February 12 - 5am February 13, 2009 (DOY
*************************** 043/1000z-044/1000z)

OBSERVATIONS SCHEDULED

ACS/SBC 11970

HST Observations of Titan's Escaping Atmosphere in Transit and in
Emission

We propose UV observations using the ACS/SBC of Titan's extended
escaping atmosphere for the Jan/Feb 2009 period of transits of Titan
across Saturn. A combination of absorption of Saturn's reflected solar
UV emission in transit, and extended emissions primarily from H atoms
away from transit, will yield new information about the structure of
Titan's extended upper atmosphere. These observations are expected to
provide new constraints on theoretical models for a hydrodynamic flow
of species through Titan's exobase level, resulting from the
interpretation of recent Cassini measurements at Titan.

FGS 11788

The Architecture of Exoplanetary Systems

Are all planetary systems coplanar? Concordance cosmogony makes that
prediction. It is, however, a prediction of extrasolar planetary
system architecture as yet untested by direct observation for main
sequence stars other than the Sun. To provide such a test, we propose
to carry out FGS astrometric studies on four stars hosting seven
companions. Our understanding of the planet formation process will
grow as we match not only system architecture, but formed planet mass
and true distance from the primary with host star characteristics for
a wide variety of host stars and exoplanet masses.

We propose that a series of FGS astrometric observations with
demonstrated 1 millisecond of arc per-observation precision can
establish the degree of coplanarity and component true masses for four
extrasolar systems: HD 202206 (brown dwarf+planet); HD 128311
(planet+planet), HD 160691 = mu Arae (planet+planet), and HD 222404AB
= gamma Cephei (planet+star). In each case the companion is identified
as such by assuming that the minimum mass is the actual mass. For the
last target, a known stellar binary system, the companion orbit is
stable only if coplanar with the AB binary orbit.

WFPC2 11944

Binaries at the Extremes of the H-R Diagram

We propose to use HST/Fine Guidance Sensor 1r to survey for binaries
among some of the most massive, least massive, and oldest stars in our
part of the Galaxy. FGS allows us to spatially resolve binary systems
that are too faint to observe using ground-based, speckle or optical
long baseline interferometry, and too close to resolve with AO. We
propose a SNAP-style program of single orbit FGS TRANS mode
observations of very massive stars in the cluster NGC 3603, luminous
blue variables, nearby low mass main sequence stars, cool subdwarf
stars, and white dwarfs. These observations will help us to (1)
identify systems suitable for follow up studies for mass
determination, (2) study the role of binaries in stellar birth and in
advanced evolutionary states, (3) explore the fundamental properties
of stars near the main sequence-brown dwarf boundary, (4) understand
the role of binaries for X-ray bright systems, (5) find binaries among
ancient and nearby subdwarf stars, and (6) help calibrate the white
dwarf mass - radius relation.

WFPC2 11967

WFPC2 Imaging of the Lockman Hole

In order to understand galaxy evolution and constrain theoretical
models, we require both multiwavelength photometry (to robustly
determine physical parameters such as star formation rates and stellar
masses) and detailed morphological information. Galaxy morphology
encodes crucial information about galaxy formation history and the
physical processes that trigger star formation and AGN activity, and
high-resolution imaging for large samples of galaxies is currently
only obtainable with HST. The Lockman Hole has been the target of
extensive multi-wavelength observations from the X-ray to the radio,
and will be the target of the deepest wide-area blankfield thermal IR
observations with Herschel, but currently lacks comprehensive HST
imaging. We propose to obtain WFPC2 imaging of ~500 arcmin2 of the
central region of the Lockman Hole in F606W and F814W, to a depth of
V606~26.8 and I814~26. This imaging is crucial in order to
characterize the sources detected at other wavelengths.

WFPC2 11986

Completing HST's Local Volume Legacy

Nearby galaxies offer one of the few laboratories within which stellar
populations can be tied to multi-wavelength observations. They are
thus essential for calibrating and interpreting key astrophysical
observables, such as broad-band luminosities, durations and energy
input from starbursts, and timescales of UV, H-alpha, and FIR
emission. The study of stellar populations in nearby galaxies requires
high-resolution observations with HST, but HST's legacy for this
limited set of galaxies remains incomplete.

As a first attempt to establish this legacy, The ACS Nearby Galaxy
Survey Treasury (ANGST) began observations in late 2006. ANGST was
designed to carry out a uniform multi-color survey of a volume-limited
sample of ~70 nearby galaxies that could be used for systematic
studies of resolved stellar populations. The resulting data provide
nuanced constraints on the processes which govern star formation and
galaxy evolution, for a well-defined population of galaxies. All
photometry for the survey has been publicly released.

However, the failure of ACS 4.5 months after ANGST began taking data
led to a drastic reduction in the planned survey. The loss is
two-fold. First, the goals of completeness and uniformity were greatly
compromised, impacting global comparison studies. Second, the variety
of observed star formation histories was reduced. Given that we have
never found two galaxies with identical star formation histories, and
fully sampling the population allows us to catch those few systems
whose star formation rates and metallicities place the strongest
constraints on key astrophysical processes.

Here we propose WFPC2 observations of all remaining galaxies within
the Local Volume (D3.5Mpc) for which current HST observations are
insufficient for meaningful stellar population studies. We will use
these observations for research on the star formation histories of
individual galaxies and the Local Volume, detailed calibrations of
star formation rate indicators, and the durations of starbursts. We
will also make them publicly available through the ANGST archive to
support future research. The proposed observations will finally
complete a lasting legacy of HST

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************** 08***************** 08
FGS REacq************** 06***************** 06
OBAD with Maneuver **** 28***************** 28

SIGNIFICANT EVENTS:* (None)