Daily # 4175

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4175

PERIOD COVERED: UT August 10, 2006 (DOY 222)

OBSERVATIONS SCHEDULED

ACS/HRC 10860

The largest Kuiper belt object

The past year has seen an explosion in the discoveries of Pluto-sized
objects in the Kuiper belt. With the discoveries of the
methane-covered 2003 UB313 and 2005 FY9, the multiple satellite system
of 2003 EL61, and the Pluto-Charon analog system of Orcus and its
satellite, it is finally apparent that Pluto is not a unique oddball
at the edge of the solar system, but rather one of a family of
similarly large objects in the Kuiper belt and beyond. HST
observations over the past decade have been critical for understanding
the interior, surface, and atmosphere of Pluto and Charon. We propose
here a comprehensive series of observations designed to similarly
expand our knowledge of these recently discovered Pluto-sized and
near-Pluto-sized Kuiper belt objects. These observations will measure
objects' sizes and densities, explore the outcome of collisions in the
outer solar system, and allow the first ever look at the interior
structure of a Kuiper belt object. Our wide field survey that
discovered all of these objects is nearly finished, so after five
years of continuous searching we are finally almost complete in our
tally of these near-Pluto-sized objects. This large HST request is the
culmination of this half-decade search for new planetary-sized
objects. As has been demonstrated repeatedly by the approximately 100
previous orbits devoted to the study of Pluto, only HST has the
resolution and sensitivity for detailed study of these distant
objects. With these new Pluto-sized objects only now being discovered
we have a limited window left to still use HST for these critical
observations.

ACS/HRC/WFC 10733

CCD Hot Pixel Annealing

Hot pixel annealing will continue to be performed once every 4 weeks.
The CCD TECs will be turned off and heaters will be activated to bring
the detector temperatures to about +20C. This state will be held for
approximately 6 hours, after which the heaters are turned off, the
TECs turned on, and the CCDs returned to normal operating condition.
To assess the effectiveness of the annealing, a bias and four dark
images will be taken before and after the annealing procedure for both
WFC and HRC. The HRC darks are taken in parallel with the WFC darks.
The charge transfer efficiency {CTE} of the ACS CCD detectors declines
as damage due to on-orbit radiation exposure accumulates. This
degradation has been closely monitored at regular intervals, because
it is likely to determine the useful lifetime of the CCDs. We combine
the annealling activity with the charge transfer efficiency monitoring
and also merge into the routine dark image collection. To this end,
the CTE monitoring exposures have been moved into this proposal . All
the data for this program is acquired using internal targets {lamps}
only, so all of the exposures should be taken during Earth occultation
time {but not during SAA passages}. This program emulates the ACS
pre-flight ground calibration and post-launch SMOV testing {program
8948}, so that results from each epoch can be directly compared.
Extended Pixel Edge Response {EPER} and First Pixel Response {FPR}
data will be obtained over a range of signal levels for both the Wide
Field Channel {WFC}, and the High Resolution Channel {HRC}.

ACS/WFC 10787

Modes of Star Formation and Nuclear Activity in an Early Universe
Laboratory

Nearby compact galaxy groups are uniquely suited to exploring the
mechanisms of star formation amid repeated and ongoing gravitational
encounters, conditions similar to those of the high redshift universe.
These dense groups host a variety of modes of star formation, and they
enable fresh insights into the role of gas in galaxy evolution. With
Spitzer mid-IR observations in hand, we have begun to obtain high
quality, multi-wavelength data for a well-defined sample of 12 nearby
{4500km/s} compact groups covering the full range of evolutionary
stages. Here we propose to obtain sensitive BVI images with the
ACS/WFC, deep enough to reach the turnover of the globular cluster
luminosity function, and WFPC2 U-band and ACS H-alpha images of
Spitzer- identified regions hosting the most recent star formation. In
total, we expect to detect over 1000 young star clusters forming
inside and outside galaxies, more than 4000 old globular clusters in
40 giant galaxies {including 16 early-type galaxies}, over 20 tidal
features, approximately 15 AGNs, and intragroup gas in most of the 12
groups. Combining the proposed ACS images with Chandra observations,
UV GALEX observations, ground-based H-alpha imaging, and HI data, we
will conduct a detailed study of stellar nurseries, dust, gas
kinematics, and AGN.

ACS/WFC 10816

The Formation History of Andromeda's Extended Metal-Poor Halo

We propose deep ACS imaging in the outer spheroid of the Andromeda
galaxy, in order to measure the star formation history of its true
halo. For the past 20 years, nearly all studies of the Andromeda
"halo" were focused on the spheroid within 30 kpc of the galaxy's
center, a region now known to host significant substructure and
populations with high metallicity and intermediate ages. However, two
groups have recently discovered an extended metal-poor halo beyond 30
kpc; this population is distinct in its surface-brightness profile,
abundance distribution, and kinematics. In earlier cycles, we obtained
deep images of the inner spheroid {11 kpc on the minor axis}, outer
disk {25 kpc on the major axis}, and giant tidal stream, yielding the
complete star formation history in each field. We now propose deep ACS
imaging of 4 fields bracketing this 30 kpc transition point in the
spheroid, so that the inner spheroid and the extended halo populations
can be disentangled, enabling a reconstruction of the star formation
history in the halo. A wide age distribution in the halo, as found in
the inner spheroid, would imply the halo was assembled through ongoing
accretion of satellite galaxies, while a uniformly old population
would be a strong indication that the halo was formed during the early
rapid collapse of the Andromeda proto-galaxy.

FGS 10611

Precise Distances to Nearby Planetary Nebulae

We propose to carry out astrometry with the FGS to obtain accurate and
precise distances to four nearby planetary nebulae. In 1992, Cahn et
al. noted that ``The distances to Galactic planetary nebulae remain a
serious, if not THE most serious, problem in the field, despite
decades of study.'' Twelve years later, the same statement still
applies. Because the distances to planetary nebulae are so uncertain,
our understanding of their masses, luminosities, scale height, birth
rate, and evolutionary state is severely limited. To help remedy this
problem, HST astrometry can guarantee parallaxes with half the error
of any other available approach. These data, when combined with
parallax measurements from the USNO, will improve distance
measurements by more than a factor of two, producing more accurate
distances with uncertainties that are of the order of ~6%. Lastly,
most planetary nebula distance scales in the literature are
statistical. They require several anchor points of known distance in
order to calibrate their zero point. Our program will provide "gold
standard" anchor points by the end of 2006, a decade before any
anticipated results from future space astrometry missions.

NIC1 10879

A search for planetary-mass companions to the nearest L dwarfs -
completing the survey

We propose to extend the most sensitive survey yet undertaken for very
low-mass companions to ultracool dwarfs. We will use NICMOS to
complete imaging of an all-sky sample of 87 L dwarfs in 80 systems
within 20 parsecs of the Sun. The combination of infrared imaging and
proximity allows us to search for companions with mass ratios q0.25
at separations exceeding ~3 AU, while probing companions with q0.5 at
~1.5 AU separation. This resolution is crucial, since no ultracool
binaries are known in the field with separations exceeding 15 AU.
Fifty L dwarfs from the 20-parsec sample have high-resolution imaging,
primarily through our Cycle 13 HST proposal which identified six new
binaries, including an L/T system. Here, we propose to target the
remaining 30 dwarfs

NIC1/NC2/NC3 10723

Cycle 14 NICMOS dark current, shading profile, and read noise
monitoring program

The purpose of this proposal is to monitor the dark current, read
noise, and shading profile for all three NICMOS detectors throughout
the duration of Cycle 14. This proposal is a slightly modified version
of proposal 10380 of cycle 13 and 9993 of cycle12 that we cut down
some exposure time to make the observation fit within 24 orbits.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

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.

NIC2 10847

Coronagraphic Polarimetry of HST-Resolved Debris Disks

We propose to take full advantage of the recently commissioned
coronagraphic polarimetry modes of ACS and NICMOS to obtain imaging
polarimetry of circumstellar debris disks that were imaged previously
by the HST coronagraphs, but without the polarizers. It is well
established that stars form in gas-rich protostellar disks, and that
the planets of our solar system formed from a circum-solar disk.
However, the connection between the circumstellar disks that we
observe around other stars and the processes of planet formation is
still very uncertain. Mid-IR spectral studies have suggested that disk
grains are growing in the environments of young stellar objects during
the putative planet-formation epoch. Furthermore, structures revealed
in well resolved images of circumstellar disks suggest gravitational
influences on the disks from co-orbital bodies of planetary mass.
Unfortunately, existing imaging data provides only rudimentary
information abou the disk grains and their environments. Our proposed
observations, which can be obtained only with HST, will enable us to
quantitatively determine the sizes of the grains and optical depths as
functions of their location within the disks {i.e., detailed
tomography}. Armed with these well-determine physical and geometrical
systemic parameters, we will develop a set of self-consistent models
of disk structures to investigate possible interactions between unseen
planets and the disks from which they formed. Our results will also
calibrate models of the thermal emission from these disks, that will
in turn enable us to infer the properties of other debris disks that
cannot be spatially resolved with current or planned instruments and
telescopes.

WFPC2 10631

Intermediate-Age Globular Clusters in M31

We propose deep ACS/WFC imaging of four halo M31 globular clusters in
order to derive their horizontal branch morphologies. Our
spectroscopic investigation of their integrated light identifies them
as members of an intermediate-age population of globular clusters in
M31. Since our spectroscopic results are based on the analysis of
Balmer absorption lines, we need to secure our results against an
artificial juvenation due to extreme horizontal branch morphologies.
The proposed observations will allow a clear-cut answer to the
question of whether spectroscopically derived intermediate-age
estimates are due to genuinely younger ages or are the result of
anomalously hot horizontal branch morphologies. Either way, our
results will have important implications for spectroscopically derived
ages and metallicities of distant stellar populations. Because of the
high spatial resolution of the proposed ACS/WFC observations we will
also derive accurate surface brightness profiles of our target
globular clusters and investigate the influence of stellar density on
horizontal branch morphology. Moreover, together with deep parallel
WFPC2 fields we will study the metallicity dispersion of the
background stellar population in M31 as a function of galactocentric
radius.

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 07 07
FGS REacq 07 07
OBAD with Maneuver 28 28

SIGNIFICANT EVENTS: (None)