Daily # 4178

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4178

PERIOD COVERED: UT August 15, 2006 (DOY 227)

OBSERVATIONS SCHEDULED

ACS/HRC 10909

Exploring the diversity of cosmic explosions: The supernovae of
gamma-ray bursts

While the connection between gamma-ray bursts {GRBs} and supernovae
{SNe} is now clearly established, there is a large variety of
observational properties among these SNe and the physical parameters
of these explosions are poorly known. As part of a comprehensive
program, we propose to use HST in order to obtain basic information
about the supernovae associated with gamma-ray bursts. HST offers the
means to cleanly separate the light curves of the GRB afterglow from
the supernova, and to remove the contamination from the host galaxy,
opening a clear route to the fundamental parameters of the SN. From
these observations, we will determine the absolute magnitude at
maximum, the shape of the spectral energy distribution, and any change
over time of the energy distribution. We will also measure the rate of
decay of the exponential tail. Merged with the ground-based data that
we will obtain for each event, we will be able to compare our data set
to models and constrain the energy of the explosion, the mass of the
ejecta and the mass of Nickel synthesized during the explosion. These
results will shed light on the apparent variety of supernovae
associated with gamma-ray bursts and X-ray flashes, and on the
relation between these SNe and other, more common varieties of core-
collapse explosions.

ACS/SBC 10184

A New Class of Bright Ultraviolet Variable Sources in the Globular
Cluster NGC 1851

Our reductions of archival STIS/FUV-MAMA data {AR9225} have discovered
13 completely unexpected and unexplained Ultraviolet bright variables.
Eleven of the variables have been identified with evolved stars
{Horizontal Branch or Asymptotic Giant Branch}. The total number and
nature of these systems is completely unknown. If these variables are
binaries the implication is that the binary fraction {up to 25%} in
NGC 1851 is the highest in all Galactic globular clusters. The radial
distributions of the variables and the blue horizontal branch stars
imply a common origin and perhaps an explanation of the bi-modal
morphology of the horizontal branch in the color magnitude diagrams of
globular clusters. These variables may be the tip of the iceberg and a
critical clue concerning the infamous "second parameter". We propose
to observe NGC 1851 on three occasions with the same setup as the
archival data to determine the total number and periods of the
ultraviolet variables.

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.

ACS/WFC 10881

The Ultimate Gravitational Lensing Survey of Cluster Mass and
Substructure

We propose a systematic and detailed investigation of the mass,
substructure, and thermodynamics of one hundred X-ray luminous galaxy
clusters at 0.15z0.3. The primary goal is to test our recent
suggestion that this population is dominated by dynamically immature
disturbed clusters, and that the observed mass-temperature relation
suffers strong structural segregation. If confirmed, this would
represent a paradigm shift in our observational understanding of
clusters, that were hitherto believed to be dominated by mature,
undisturbed systems. The key observation to this endeavor is Hubble
imaging of cluster cores to identify robustly tangential and radial
multiple arcs and measure the shape of faint galaxies. These strong
and weak lensing signals will give an accurate measure of the total
mass and structure of the dark matter distribution that we will
subsequently compare with X-ray and Sunyaev Zeldovich Effect
observables. The broader applications of our project include 1} the
calibration of mass-temperature and mass-SZE scaling relations which
will be critical for the calibration of proposed dark energy
experiments, and 2} the low redshift baseline study of the
demographics of massive clusters to aid interpretation of future high
redshift {z1} cluster samples. For this ultimate cluster survey, we
request ACS SNAPSHOTS through the F606W filter drawn from a target
list of 143 clusters.

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.

WFPC2 10745

WFPC2 CYCLE 14 INTERNAL MONITOR

This calibration proposal is the Cycle 14 routine internal monitor for
WFPC2, to be run weekly to monitor the health of the cameras. A
variety of internal exposures are obtained in order to provide a
monitor of the integrity of the CCD camera electronics in both bays
{both gain 7 and gain 15 -- to test stability of gains and bias
levels}, a test for quantum efficiency in the CCDs, and a monitor for
possible buildup of contaminants on the CCD windows. These also
provide raw data for generating annual super-bias reference files for
the calibration pipeline.

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 07 07
OBAD with Maneuver 30 30

SIGNIFICANT EVENTS:

BB SPA Back On-Line Flash Report

As the battery temperatures have decreased to acceptable levels, per
plan the -BB SPA trim relay was successfully placed back on-line in
hardware and FSW. The commanding was executed at approximately DOY
2006/227 15:17 GMT via Ops Request 17892. EPS SE monitored the system
for one orbit and observed nominal battery temperatures cycling below
2 deg C. In addition, the SA section 1 & 5 anomaly is still present
with the same signature of ~1.8 amps reduction in SA section 1 current
and an increase of ~1.8 amps in SA section 5 current when battery 5
reaches cut-off.