Daily Report #4179

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4179

PERIOD COVERED: UT August 16, 2006 (DOY 228)

OBSERVATIONS SCHEDULED

ACS/HRC 10870

The Ring Plane Crossings of Uranus in 2007

The rings of Uranus turn edge-on to Earth in May and August 2007. In
between, we will have a rare opportunity to see the unlit face of the
rings. With the nine optically thick rings essentially invisible, we
will observe features and phenomena that are normally lost in their
glare. We will use this opportunity to search thoroughly for the
embedded "shepherd" moons long believed to confine the edges of the
rings, setting a mass limit roughly 10 times smaller than that of the
smallest shepherd currently known, Cordelia. We will measure the
vertical thicknesses of the rings and study the faint dust belts only
known to exist from a single Voyager image. We will also study the
colors of the newly-discovered faint, outer rings; recent evidence
suggests that one ring is red and the other blue, implying that each
ring is dominated by a different set of physical processes. We will
employ near-edge-on photometry from 2006 and 2007 to derive the
particle filling factor within the rings, to observe how ring epsilon
responds to the "traffic jam" as particles pass through its narrowest
point, and to test the latest models for preserving eccentricities and
apse alignment within the rings. Moreover, this data set will allow us
to continue monitoring the motions of the inner moons, which have been
found to show possibly chaotic orbital variations; by nearly doubling
the time span of the existing ACS astrometry, the details of the
variations will become much clearer.

ACS/HRC/WFC 10758

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This programme will be
for the entire lifetime of ACS. Changes from cycle 13:- The default
gain for WFC is 2 e-/DN. As before bias frames will be collected for
both gain 1 and gain 2. Dark frames are acquired using the default
gain {2}. This program cover the period May, 31 2006- Oct, 1-2006. The
first half of the program has a different proposal number: 10729.

ACS/HRC/WFC 10896

An Efficient ACS Coronagraphic Survey for Debris Disks around Nearby
Stars

We propose to finish our Cycle 11 optical survey for nearby debris
disks using the ACS/HRC coronagraph. Out of 43 orbits originally
proposed for the survey, 23 orbits were allocated, leading to a survey
of 22 stars, from which two new debris disks were imaged for the first
time. Our analysis of the initial survey gives an empirical estimate
for the detection rate of debris disks relative to heliocentric
distance and dust optical depth. Our target list for Cycle 15 is now
optimized to yield more frequent disk detections. Likewise our
observing strategy is improved to maximize sensitivity per telescope
orbit allocated. Therefore we present the most efficient survey
possible. The scientific motivation is to obtain scattered light
images of previously unresolved debris disks to determine their
viewing geometry and physical architecture, both of which may
characterize the underlying planetary system. We choose 25 debris disk
targets for which we predict a detection rate of 25% ? 5%. Four
targets have extrasolar planets from which the viewing geometry
revealed by a disk detection will resolve the v sin{i} ambiguity in
the planet masses. These targets present the remarkable opportunity of
finally seeing a debris disk in system with known planets.

ACS/WFC 10592

An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in
the Local Universe

At luminosities above 10^11.4 L_sun, the space density of far-infrared
selected galaxies exceeds that of optically selected galaxies. These
`luminous infrared galaxies' {LIRGs} are primarily interacting or
merging disk galaxies undergoing enhanced star formation and Active
Galactic Nuclei {AGN} activity, possibly triggered as the objects
transform into massive S0 and elliptical merger remnants. We propose
ACS/WFC imaging of a complete sample of 88 L_IR 10^11.4 L_sun
luminous infrared galaxies in the IRAS Revised Bright Galaxy Sample
{RBGS: i.e., 60 micron flux density 5.24 Jy}. This sample is ideal
not only in its completeness and sample size, but also in the
proximity and brightness of the galaxies. The superb sensitivity,
resolution, and field of view of ACS/WFC on HST enables a unique
opportunity to study the detailed structure of galaxies that sample
all stages of the merger process. Imaging will be done with the F439W
and F814W filters {B and I-band} to examine as a function of both
luminosity and merger state {i} the evidence at optical wavelengths of
star formation and AGN activity and the manner in which instabilities
{bars and bridges} in the galaxies may funnel material to these active
regions, {ii} the relationship between star formation and AGN
activity, and {iii} the structural properties {AGN, bulge, and disk
components} and fundamental parameters {effective radius and surface
brightness} of LIRGs and their similarity with putative evolutionary
byproducts {elliptical, S0 and classical AGN host galaxies}. This HST
survey will also bridge the wavelength gap between a Spitzer imaging
survey {covering seven bands in the 3.6-160 micron range} and a GALEX
UV imaging survey of these galaxies, but will resolve complexes of
star clusters and multiple nuclei at resolutions well beyond the
capabilities of either Spitzer or GALEX. The combined datasets will
result in the most comprehensive multiwavelength study of interacting
and merging galaxies to date.

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.

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:

10404 - GSacq(2,1,2) failed. @ 228/10:15:57z

GSacq(2,1,2) failed to RGA control (FGS Coarse Track failed - Timed
out waiting for data valid ) was received.

10405 - ACS 954 GS Acquisition failure.

At 228/10:23:12 ACS 954 (TDF was down when small angle maneuver was
commanded during a target acquisition) was received due to GSacq
failure.


COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 08 07
FGS REacq 07 07
OBAD with Maneuver 30 30

SIGNIFICANT EVENTS: (None)