Daily 3828

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 3828

PERIOD COVERED: DOY 89

OBSERVATIONS SCHEDULED

ACS/HRC/WFC 10367

ACS CCDs daily monitor- cycle 13 - part 1

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.

ACS/WFC/NIC/NIC3/WFPC 10246 2 The HST survey of the Orion Nebula
Cluster

We propose a Treasury Program of 104 HST orbits to perform the
definitive study of the Orion Nebula Cluster, the Rosetta stone of
star formation. We will cover with unprecedented sensitivity {23-25
mag}, dynamic range {~12 mag}, spatial resolution {50mas}, and
simultaneous spectral coverage {5 bands} a ~450 square arcmin field
centered on the Trapezium stars. This represents a tremendous gain
over the shallow WFC1 study made in 1991 with the aberrated HST on an
area ~15 times smaller. We maximize the HST observing efficiency using
ACS/WFC and WFPC2 in parallel with two opposite roll angles, to cover
the same total field. We will assemble the richest, most accurate and
unbiased HR diagram for pre-main-sequence objects ever made. Combined
with the optical spectroscopy already available for ~1000 sources and
new deep near-IR imaging and spectroscopy {that we propose as Joint
HST-NOAO observations}, we will be able to attack and possibly solve
the most compelling questions on stellar evolution: the calibration of
pre-main-sequence evolutionary tracks, mass segration and the
variation of the initial mass function in different environments, the
evolution of mass accretion rates vs. age and environment, disk
dissipation in environments dominated by hard vs. soft-UV radiation,
stellar multiplicity vs. disk fraction. In addition, we expect to
discover and classify an unknown, but substantial, population of
pre-Main Sequence binaries, low mass stars and brown dwarfs down to
~10 MJup. This is also the best possible way to discover dark
silhouette disks in the outskirts of the Orion Nebula and study their
evolutionary status through multicolor imaging. This program is timely
and extremely well leveraged to other programs targeting Orion: the
ACS H-alpha survey of the Orion Nebula, the recently completed 850ks
ultradeep Chandra survey, the large GTO programs to be performed with
SIRTF, plus the availability of 2MASS and various deep JHK surveys of
the core recently done with 8m class telescopes.

ACS/WFC/WFPC2 10241

An ACS H-alpha Survey of the Carina Nebula

We propose an H-alpha ACS imaging survey covering 540 square
arcminutes of the Carina Nebula, including an unbiased survey of the
bright core, and several prominent dust pillars in the rich southern
region of the nebula. Carina provides an important link between
well-studied nearby H II regions like Orion, and more distant
mini-starbusts like 30 Doradus. CVZ orbits will allow extremely
efficient use of HST to map a large area of this complex and important
region -- more than 95 percent of the proposed survey will be observed
by HST for the first time. This survey will provide a complete census
of microjets, proplyds, and silhouette disks with diameters as small
as 200 AU, enough to spatially resolve disks like those in Orion, and
will provide the first catalog of outflows {jets} from embedded
low-mass stars, thin filamentary shocks, and wind-wind collisions in
Carina. An accurate census of these phenomena is needed to
characterize the star formation activity and gas dynamics as a
function of position in the nebula, and to determine if models for
protoplanetary disk evaporation from Orion are applicable in more
extreme regions. Our previous ground-based optical and IR surveys have
already revealed dozens of candidates for this type of activity -- but
this is just the tip of the iceberg. Our proposed HST/ACS survey
promises to be a bonanza for understanding ongoing low-mass star
formation influenced by extremely high-mass stars.

ACS/WFC/WFPC2 10424

The White Dwarf Cooling Age and Dynamical History of the Metal-Poor
Globular Cluster NGC 6397

We propose to determine the white dwarf cooling age in the nearest
metal-poor {[Fe/H]=- 2} globular cluster, NGC 6397. This globular
cluster provides the best opportunity to test the white dwarf cooling
age in such a metal-poor system and at the same time provide a
comparison with the more metal-rich cluster {M4} which we recently
successfully observed with HST. Any {or even no} age difference
between these clusters will be important in understanding the
age-metallicity relation for these systems which reflects the star
formation history in the early Galaxy. The absolute age is an
important cosmological constraint. We expect to be able to detect age
DIFFERENCES between these clusters at the 0.5 Gyr level and absolute
ages should be accurate to 1.0 Gyr. In addition, and in contrast with
M4, NGC 6397 is highly dynamically evolved, has a collapsed core, and
the distribution of its white dwarfs throughout the cluster have
almost certainly been modified by dynamical processes. We are using
N-body simulations specifically developed for this cluster to
understand these modifications and to include their effects in our
measurement of the white dwarf luminosity function and cooling age.
Among the dynamical questions we expect to answer with this proposal
a 1} what was the primordial binary frequency in NGC 6397? 2} can
we explain the high central concentration with a population of massive
white dwarfs and/or neutron stars? 3} do we see sufficient central
binaries to reverse the core collapse of the cluster?

FGS 10108

Dynamical Masses and Radii of Four White Dwarf Stars

The cool white dwarf stars WD1639+153 and WD1818+126 were recently
resolved by HST FGS1r to be double degenerate binary systems with
projected separations of 112 mas and 174 mas respectively. At a
distance of less than 50 pc they may both have periods shorter than
about 20 years, making them ideal candidates for follow up studies for
dynamical mass determinations. This will increase the number of white
dwarfs with dynamical mass measurements from the current 4 up to 8.
Continued observations of these white dwarfs along with nearby field
stars with the FGS will accurately determine the orbital elements and
parallax of each system. The mass and radius of all four white dwarfs
can be determined to an unprecedented 1%, making it possible to test
and calibrate the theoretical white dwarf mass radius relation at the
cool end of the cooling curve for the DA and DC subclasses. Since the
components of the binary are coeval, once the mass and radius, and
hence the cooling age of each star is known, it will be possible to
estimate the relation between the initial mass and final mass for all
four white dwarfs. We are requesting a total of 4 HST orbits per year
for the next three cycles to initiate the process that will result in
a determination of the mass and radius of the four white dwarfs.

NIC1/NIC2/NIC3 8792

NICMOS Post-SAA calibration - CR Persistence Part 3

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 10177

Solar Systems In Formation: A NICMOS Coronagraphic Survey of
Protoplanetary and Debris Disks

Until recently, despite decades of concerted effort applied to
understanding the formation processes that gave birth to our solar
system, the detailed morphology of circumstellar material that must
eventually form planets has been virtually impossible to discern. The
advent of high contrast, coronagraphic imaging as implemented with the
instruments aboard HST has dramatically enhanced our understanding of
natal planetary system formation. Even so, only a handful of evolved
disks {~ 1 Myr and older} have been imaged and spatially resolved in
light scattered from their constituent grains. To elucidate the
physical processes and properties in potentially planet-forming
circumstellar disks, and to understand the nature and evolution of
their grains, a larger spatially resolved and photometrically reliable
sample of such systems must be observed. Thus, we propose a highly
sensitive circumstellar disk imaging survey of a well-defined and
carefully selected sample of YSOs {1-10 Myr T Tau and HAeBe stars} and
{ app 10 Myr} main sequence stars, to probe the posited epoch of
planetary system formation, and to provide this critically needed
imagery. Our resolved images will shed light on the spatial
distributions of the dust in these thermally emissive disks. In
combination with their long wavelength SEDs the physical properties of
the grains will be discerned, or constrained by our photometrically
accurate surface brightness sensitivity limits for faint disks which
elude detection. Our sample builds on the success of the exploratory
GTO 7233 program, using two-roll per orbit PSF-subtracted NICMOS
coronagraphy to provide the highest detection sensitivity to the
smallest disks around bright stars which can be imaged with HST. Our
sample will discriminate between proposed evolutionary scenarios while
providing a legacy of cataloged morphologies for interpreting mid- and
far-IR SEDs that the recently launched Spitzer Space Telescope will
deliver.

FLIGHT OPERATIONS SUMMARY:

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

COMPLETED OPS REQs: None


OPS NOTES EXECUTED: None


SCHEDULED SUCCESSFUL FAILURE TIMES
FGS Gsacq 09 09
FGS Reacq 07 07
FHST Update 12 12
LOSS of LOCK



SIGNIFICANT EVENTS: None