Daily Report #4831

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT***** #4831

PERIOD COVERED: 5am April 10 - 5am April 13, 2009 (DOY
************************** 100/0900z-103/0900z)

OBSERVATIONS SCHEDULED

WFPC2 11990

Determining the Physical Properties of Comet 103P/Hartley 2 in Support
of NASA's EPOXI Mission

We request 12 orbits of imaging to measure the size, shape, and
rotation period of the nucleus of comet 103P/Hartley 2, the target of
NASA's EPOXI mission. Knowledge of rotation period at the 20% level is
required early to plan the mission sequencing, and the only time to
secure these observations before the coma signal dominates the nucleus
is during the first half of 2009. As demonstrated by the international
campaigns to determine the rotation period of comet 9P/Tempel 1 for
both the Deep Impact and Stardust-NExT missions, spacecraft and
Earth-based observations can be combined to achieve unprecedented
accuracy on the rotation of the nucleus. For comet Tempel 1 this has
led to paradigm-changing ideas about the physical processes
responsible for cometary activity. The nucleus flyby of 103P/Hartley 2
on 2010 November 4 presents another opportunity for unique science
enabled by combining ground-based and in-situ observations. The size
and shape of the comet's nucleus are currently uncertain, and the
rotation period is completely unknown. Hubble observations are
uniquely suited to measure the physical properties of this nucleus.

WFPC2 11987

The Recent Star Formation History of SINGS Galaxies

The Spitzer Legacy project SINGS provided a unique view of the current
state of star formation and dust in a sample of galaxies of all Hubble
types. This multi-wavelength view allowed the team to create current
star formation diagnostics that are independent of the dust content
and increased our understanding of the dust in galaxies. Even so,
using the SINGS data alone we can only make rough estimates of the
recent star formation history of these galaxies. The lack of U-band
observations means that it is impossible to estimate the ages of young
clusters. In addition, the low resolution of the Spitzer and
ground-based observations means that what appear to be individual
Spitzer sources can actually be composed of many individual clusters
with varying ages. In this proposal we plan to address this missing
area in SINGS by obtaining high-resolution WFPC2 UBVI observations to
accurately find and determine the ages of the young stellar clusters
in a subset of the SINGS galaxies. These observations will greatly
enhance the legacy value of the SINGS observations while also directly
answering questions pertaining to star formation in galaxies.

ACS/SBC 11982

Spanning the Reionization History of IGM Helium: a Large and Efficient
HST Spectral Survey of Far-UV-Bright Quasars

The reionization of IGM helium is thought to have occurred at
redshifts of z=3 to 4. Detailed studies of HeII Lyman-alpha absorption
toward a handful of QSOs at 2.7z3.3 demonstrated the high potential
of such IGM probes, but the small sample size and redshift range limit
confidence in cosmological inferences. The requisite unobscured
sightlines to high-z are extremely rare, but we've cross-correlated
10, 000 z2.8 SDSS DR7 (and other) quasars with GALEX GR4 UV sources
to obtain 550 new, high confidence, sightlines potentially useful for
HST HeII studies; and in cycle 15-16 trials we demonstrated the
efficacy of our SDSS/GALEX selection approach identifying 9 new HeII
quasars at unprecedented 67% efficiency. We propose the first
far-UV-bright HeII quasar survey that is both large in scale and also
efficient, via 2-orbit reconnaissance ACS/SBC prism spectra toward a
highly select subset of 40 new SDSS/GALEX quasars at 3.1z5.1. These
will provide a community resource list that includes 5 far-UV-bright
(restframe) HeII sightlines in each of 8 redshift bins spanning
3.1z3.9 (and perhaps several objects at z4), enabling superb
post-SM4 follow-up spectra with COS or STIS. But simultaneously and
independent of any SM4 uncertainties, we will hereby directly obtain
10-orbit UV spectral stacks from the 5 HeII quasars in each of the 8
redshift bins to trace the reionization history of IGM helium over at
least 3.1z3.9. These spectral stacks will average over cosmic
variance and individual object pathology. Our new high-yield HeII
sightline sample and spectral stacks, covering a large redshift range,
will allow confident conclusions about the spectrum and evolution of
the ionizing background, the evolution of HeII opacity, the density of
IGM baryons, and the epoch of helium reionization.

WFPC2 11978

Luminous and Dark Matter in Disk Galaxies from Strong Lensing and
Stellar Kinematics

The formation of realistic disk galaxies within the LCDM paradigm is
still an unsolved problem. Theory is only now beginning to make
predictions for how dark matter halos respond to galaxy formation and
for the properties of disk galaxies. Measuring the density profiles of
dark matter halos on galaxy scales is therefore a strong test for the
standard paradigm of galaxy formation, offering great potential for
discovery. However, from an observational point of view, the
degeneracy between the stellar and dark matter contributions to galaxy
rotation curves remains a major road block. Strong gravitational
lensing, when coupled to spatially-resolved kinematics and stellar
population models, can solve this long-standing problem.
Unfortunately, this joint methodology could not be exploited so far
due to the paucity of known edge-on spiral lenses. Exploiting the full
SDSS-DR7 archive we have identified a new sample of exactly these
systems. We propose multi-color HST imaging to confirm and measure a
sample of twenty spiral lenses, covering a range of bulge to disk
ratios. By combining dynamical lensing and stellar population
information for this unique sample we will deliver the first
statistical constraints on halos and disk properties, and a new
stringent test of disk galaxy formation theories.

WFPC2 11975

UV Light from Old Stellar Populations: a Census of UV Sources in
Galactic Globular Clusters

In spite of the fact that HST has been the only operative
high-resolution eye in the UV-window over the last 18 years, no
homogeneous UV survey of Galactic globular clusters (GGCs) has been
performed to date. In order to fill this gap in the stellar population
studies, we propose a program that exploits the unique capability of
the WFPC2 and the SBC in the far-/mid- UV for securing deep UV imaging
of 46 GGCs. The proposed observations will allow to study with
unprecedented accuracy the hottest GGC stars, comprising the extreme
horizontal branch (HB) stars and their progeny (the so-called
AGB-manque', and Post-early AGB stars), and "exotic stellar
populations" like the blue straggler stars and the interacting
binaries. The targets have been selected to properly sample the GGC
metallicity/structural parameter space, thus to unveil any possible
correlation between the properties of the hot stellar populations and
the cluster characteristics. In addition, most of the targets have
extended HB "blue tails", that can be properly studied only by means
of deep UV observations, especially in the far-UV filters like the
F160BW, that is not foreseen on the WFC3. This data base is
complemented with GALEX observations in the cluster outermost regions,
thus allowing to investigate any possible trend of the UV-bright
stellar types over the entire radial extension of the clusters.
Although the hottest GGC stars are just a small class of "special"
objects, their study has a broad relevance in the context of structure
formation and chemical evolution in the early Universe, bringing
precious information on the basic star formation processes and the
origin of blue light from galaxies. Indeed, the proposed observations
will provide the community with an unprecedented data set suitable for
addressing a number of still open astrophysical questions, ranging
from the main drivers of the HB morphology and the mass loss
processes, to the origin of the UV upturn in elliptical galaxies, the
dating of distant systems from integrated light, and the complex
interplay between stellar evolution and dynamics in dense stellar
aggregates. In the spirit of constructing a community resource, we
entirely waive the proprietary period for these observations.

FGS 11944/11943

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.

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 11316

HST Cycle 16 & Pre-SM4 Optical Monitor

This is a continuation of the Cycle 15 & pre-SM4 Optical Monitor,
11020. Please see that proposal for a more complete description of the
observing strategy. The 6 visits comprising this proposal observe two
single standard stars with WFPC2/PC in order to establish overall OTA
focal length for the purposes of focus maintenance. The goal of this
monitoring before SM4 is to establish a best estimate of the OTA focus
entering SMOV.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

11767 - GSAcq (2,3,2) scheduled from 100/22:37:13 - 22:45:18 failed to
RGA Hold due to QF2STOPF and QSTOP flag indications on FGS-2

Observations affected: Astrometry, Proposal ID# 11944

11768 - GSAcq (1,2,2) at 102/09:20:45 failed to RGA control at
102/09:24:59 with QF1STOPF and QSTOP flags set.

Observations affected: WFPC 149 - 151, Proposal ID# 11987.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

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

FGS GSAcq************** 25**************** 23
FGS REAcq************** 19**************** 19
OBAD with Maneuver **** 88**************** 88

SIGNIFICANT EVENTS: (None)