Daily 3671

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 3671

PERIOD COVERED: DOY 223

OBSERVATIONS SCHEDULED

ACS/HRC 10130

Systemic Proper Motions of the Magellanic Clouds from Astrometry with
ACS: II. Second Epoch Images

We request second epoch observations with ACS of Magellanic Cloud
fields centered on the 40 quasars in the LMC and SMC for which we have
first epoch Cycle 11 data. The new data will determine the systemic
proper motion of the Clouds. An extensive astrometric analysis of the
first epoch data shows that follow-up observations with a two year
baseline will allow us to measure the proper motion of the clouds to
within 0.022 mas/year in each of the two orthogonal directions
{assuming that we can image 25 quasars, i.e., with a realistic
Snapshot Program completion rate}. The best weighted combination of
all previous measurements has a seven times larger error than what we
expect. We will determine the proper motion of the clouds with 2%
accuracy. When combined with HI data for the Magellanic Stream this
will constrain both the mass distribution in the Galactic Halo and
theoretical models for the origin of the Magellanic Stream. Previous
measurements are too crude for such constraints. Our data will provide
by far the most accurate proper motion measurement for any Milky Way
satellite.

ACS/HRC/WFC 10061

CCD Daily Monitor

This program consists of basic tests to monitor, the read noise, the
development of hot pixels and test for any source of noise in ACS CCD
detectors. This programme will be executed once a day for the entire
lifetime of ACS.

ACS/WFC 10046

CCD Hot Pixel Annealing

Hot pixel annealing will 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
12 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 this procedure, a bias and two dark images will be
taken after the annealing procedure for both WFC and HRC. The HRC
darks are taken in parallel with the WFC darks.

ACS/WFC 10210

Groups of Dwarf Galaxies: Pools of Mostly Dark Matter?

Within 5 Mpc, there are 6 groups with well-known luminous galaxies but
there also appears to be a comparable number of groups containing only
dwarfs. If these dwarf entities are truly bound then M/L values are an
order of magnitude higher than values found for groups with luminous
spiral galaxies. There are theoretical reasons to anticipate that low
mass halos may frequently be mostly dark. The dynamical influence of
low mass halos is negligible in familiar groups with luminous members.
By contrast, a study of the dynamics of `groups of dwarfs' may provide
direct evidence of the existence of dark matter potential wells with
few baryons. The goal of the present study is to gather detailed
information on the 3-D distribution of dwarf galaxies suspected to lie
within 7 groups of dwarfs within 5 Mpc. Distances with 7% relative
accuracy can be measured with the Tip of the Giant Branch method with
ACS and integrations within 1 orbit per target.

ACS/WFC 10260

The Most Massive Star Clusters: Supermassive Globular Clusters or
Dwarf Galaxy Nuclei?

Evidence is mounting that the most massive globular clusters, such as
Omega Centauri and M31-G1, may be related to the recently discovered
"Ultra-Compact Dwarfs" and the dense nuclei of dE, N galaxies.
However, no systematic imaging investigation of these supermassive
globular clusters -- at the level of Omega Cen and beyond -- has been
done, and we do not know what fraction of them might bear the
signatures {such as large effective radii or tidal tails} of having
originated as dE nuclei. We propose to use the ACS/WFC to obtain deep
images of 18 such clusters in NGC 5128 and M31, the two nearest rich
globular cluster systems. These globulars are the richest star
clusters that can be found in nature, the biggest of them reaching
10^7 Solar masses, and they are likely to represent the results of
star formation under the densest and most extreme conditions known.
Using the profiles of the clusters including their faint outer
envelopes, we will carry out state-of-the-art dynamical modelling of
their structures, and look for any clear evidence which would indicate
that they are associated with stripped satellites. This study will
build on our previous work with STIS and WFPC2 imaging designed to
study the 'Fundamental Plane' of globular clusters. When our new work
is combined with Archival WFPC2, STIS, and ACS material, we will also
be able to construct the definitive mapping of the Fundamental Plane
of globular clusters at its uppermost mass range, and confirm whether
or not the UCD and dE, N objects occupy a different structural
parameter space.

ACS/WFC 9864

The Distance to M83

M83 is a spiral galaxy at a distance of 4-5 Mpc. It is almost face-on,
and it has been measured to support one of the largest
chemical-composition, radial metallicity gradients in the local sample
of high-luminosity spiral galaxies. It also has one of the highest
absolute levels of mean metallicity in its inner regions. As such M83
is a chemical laboratory, within which we can probe {in both a
differential and in an absolute way} the zero point, the variation and
the sensitivity of the Cepheid PL relation as a function of
metallicity.

FGS 10110

Parallaxes of Extreme Halo Subgiants: Calibrating Globular Cluster
Distances and the Ages of the Oldest Stars

The ages of the oldest stars are a key constraint on the evolution of
our Galaxy, the history of star formation, and cosmological models.
These ages are usually determined from globular clusters. However, it
is alternatively possible to determine ages of extreme Population II
subgiants in the solar neighborhood based on trigonometric parallaxes,
without any recourse to clusters. This approach completely avoids the
vexing issues of cluster distances, reddenings, and chemical
compositions. There are 3 known nearby, extremely metal-deficient Pop
II subgiants with Hipparcos parallax errors of 6-11% which are
available for such age determinations. At present, based on the latest
isochrones, the derived ages of these stars {HD 84937, HD 132475, and
HD 140283} are all close to 14 Gyr, uncomfortably close to or higher
than current estimates of the age of the universe. However, the errors
in the Hipparcos parallaxes imply uncertainties of at least 2 Gyr in
the ages of the 3 stars. We propose to measure parallaxes of these
three Pop II subgiants using HST's Fine Guidance Sensor 1R. We expect
to reduce the Hipparcos parallax error bars by factors of 5-6,
providing the most stringent test yet of current theoretical stellar
models of Pop II stars and pushing the age uncertainties to below 0.5
Gyr. These data will also provide a major new constraint on the
distance scale of globular clusters, with wide implications for
stellar evolution and the calibration of Pop II standard candles.

FGS 10202

Resolving OB Binaries in the Carina Nebula, Resuming the Survey

In March 2002 we carried out a small, high-angular resolution survey
of some of the brightest OB stars in the Carina Nebula with FGS1r in
an attempt to resolve binary systems which had thus far evaded
detection by other techniques. Of 23 stars observed, 5 new OB binaries
were discovered with component separations ranging from 0.015"
to0.325". This yield over the spatial domain of FGS1r's angular
resolution, coupled with published statistics of the incidence of OB
stars in short-period spectroscopic, and long-period visual binaries
suggests that the fraction of binarity or multiplicity among OB stars
is near unity. Our unexpected resolution of the prototype O2 If* star
HD 93129A as a 55 milli-arcsecond double is a case in point that great
care must be exercised when one attempts to establish the IMF and
upper-mass cuttoff at the high-mass end of the HR diagram. We propose
to resume the survey to observe a larger, statistically meaningful
sample of OB stars to establish a firm assessment of multiplicity at
the high-mass end of the IMF in these clusters. We will also
investigate the single-star/binary-star status of several
astrophysically important, individual stars in order to enable a
better understanding of the evolution of high-mass stars.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration - CR Persistence Part 4

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 9875

The Fundamental Plane of Massive Gas-Rich Mergers

We propose deep NICMOS H-band imaging of a carefully selected sample
of 33 luminous, late-stage galactic mergers. This program is part of a
comprehensive investigation of the most luminous mergers in the nearby
universe, the ultraluminous infrared galaxies {ULIGs}. The
high-resolution HST images will complement an extensive set of
ground-based data that include long-slit NIR spectra from a recently
approved Large VLT Programme. This unique dataset will allow us to
derive with unprecedented precision structural -and- kinematic
parameters for a large unbiased sample of objects spanning the entire
ULIG luminosity function. These data will refine the fundamental plane
of massive gas-rich mergers and enable us to answer the following
questions: {1} Do ultraluminous mergers form elliptical galaxies, and
in particular, giant ellipticals? {2} Do ULIGs evolve into optically
bright QSOs? The results from this detailed study of massive mergers
in the local universe will be relevant to understanding galaxy
formation and evolution at earlier epochs, and in particular, the
dusty sub-mm population that accounts for more than half of the star
formation at z 1.

WFPC2 10071

WFPC2 CYCLE 12 Supplemental Darks Part 3/3

This dark calibration program obtains 3 dark frames every day to
provide data for monitoring and characterizing the evolution of hot
pixels.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.) None

COMPLETED OPS REQs:
17249-0 - Battery Pressure Test Limit Update @ 223/0953z
17245-2 - Battery 1 Capacity Test (complete thru step 17; High Rate
Terminated/Low Rate begin) @ 223/2012z)

OPS NOTES EXECUTED:
1258-0 - Turn Off OSTISERR LIMIT @ 223/2117z

SCHEDULED SUCCESSFUL FAILURE TIMES
FGS GSacq 12 12
FGS REacq 4 4
FHST Update 16 16
LOSS of LOCK


SIGNIFICANT EVENTS:

In response to the continued decline in Battery State of Charge (SOC)
and in preparation for Battery 1 Capacity Test, adjusted the Battery
Pressure Test limits @ 223/09:53Z (OR 17249 with COP 4.33). The
Battery Pressure Test now protects a Battery system SOC of 160 Ampere
hours to serve as a back-stop to the Battery SOC 2 Test that will be
set to 170 Ampere hours at the end of the Battery 1 Capacity Test.

Set-up for Battery 1 Capacity Test began on schedule @ 223/09:58Z (OR
17245-2 with attached Battery 1 Capacity Test script). Discharge began
with entry into orbit night @ 223/11:02Z. The Solar Array, Section 1
was transferred to the bus and the "high rate" discharge was applied @
223/11:08Z. Completed through Step 17, High Rate Terminate/Low Rate
begin @ 223/20:21Z.