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Daily 3937



 
 
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Old September 2nd 05, 04:36 PM
Joe Cooper
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Default Daily 3937

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 3937

PERIOD COVERED: UT September 01, 2005 (DOY 244)

OBSERVATIONS SCHEDULED

ACS/HRC 10547

A SNAP Program to Obtain Complete Wavelength Coverage of Interstellar
Extinction

We propose a SNAP program to obtain ACS/HRC spectra in the near-UV
{PR200L} and near-IR {G800L} for a set of main sequence B stars with
available IUE UV spectrophotometry, optical photometry, and 2MASS IR
photometry. Together with these existing data, the new observations
will provide complete photometric and spectrophotometric coverage from
1150 to 11000 A and enable us to produce complete extinction curves
from the far-UV to the near-IR, with well- determined values of R{V}.
The proposed set of 50 program sight lines includes the full range of
interstellar extinction curve types and a wide range of color
excesses. The new data will allow us to examine variability in the
near-UV through near-IR spectral regions, including the UV-optical
"knee" and the "Very Broad Structure." We will examine the response of
these features to different interstellar environments and their
relationship to other curve features. These are largely unexplored
aspects of extinction curves which will provide additional constraints
on the properties of interstellar grains. The curves will be derived
using stellar atmosphere models to represent the intrinsic spectral
energy distributions of the program stars, eliminating the need to
observe unreddened "standard stars." This approach virtually
eliminates "mismatch error", allowing us to derive extinction curves
with much higher precision than previously possible. In addition, the
new spectra will provide higher S/N data for the peak of the 2175 A
bump than previously available.

ACS/HRC/WFC 10514

Kuiper Belt Binaries: Probes of Early Solar System Evolution

Binaries in the Kuiper Belt are a scientific windfall: in them we have
relatively fragile test particles which can be used as tracers of the
early dynamical evolution of the outer Solar System. We propose a
Snapshot program using the ACS/HRC that has a potential discovery
efficiency an order of magnitude higher than the HST observations that
have already discovered the majority of known transneptunian binaries.
By more than doubling the number of observed objects in dynamically
hot and cold subpopulations we will be able to answer, with
statistical significance, the question of whether these groups differ
in the abundance of binaries as a result of their particular dynamical
paths into the Kuiper Belt. Today's Kuiper Belt bears the imprints of
the final stages of giant-planet building and migration; binaries may
offer some of the best preserved evidence of that long-ago era.

ACS/SBC 9806

Properties of the Intergalactic Medium near the Epoch of HeII
Reionization

Our STIS spectral snapshot programs have found a rare case of a He-II
Lyman-alpha absorption trough in a z=3.51, V=17.6 quasar. This is the
highest redshift at which this feature has been observed. We propose
to obtain a high-quality STIS spectrum that will enable us to {1}
Investigate the evolution and properties of the intergalactic medium
{IGM} over an epoch between z=2.8 and 3.5; {2} Search for signs of the
reionization of the intergalactic helium; {3} Measure the intensity of
the UV background radiation, and find clues toward its origin; and {4}
Estimate the IGM baryonic density. The instrument has been changed
from STIS to ASC prism.

ACS/WFC 10523

The Halo Shape and Metallicity of Massive Spiral Galaxies

We propose to resolve the stellar populations of the halos of seven
nearby, massive disk galaxies using a SNAP survey with WFC/ACS. These
observations will provide star counts and color-magnitude diagrams 2-3
magnitudes below the tip of the Red Giant Branch along the two
principal axes and one intermediate axis of each galaxy. We will
measure the metallicity distribution functions and stellar density
profiles from star counts down to very low average surface
brightnesses, equivalent to ~31 V-mag per square arcsec. This proposal
will create a unique sampling of galaxy halo properties, as our
targets cover a range in galaxy mass, luminosity, inclination, and
morphology. As function of these galaxy properties this survey will
provide:- the first systematic measurement of radial light profiles
and axial ratios of the diffuse stellar halos and outer disks of
spiral galaxies- a comprehensive analysis of halo metallicity
distributions as function of galaxy type and position within the
galaxy- an unprecedented study of the stellar metallicity and age
distribution in the outer disk regions where the disk truncations
occur- the first comparative study of globular clusters and their
field stellar populations We will use these fossil records of the
galaxy assembly process to test halo formation models within the
hierarchical galaxy formation scheme.

ACS/WFC 10550

The Nature of LSB galaxies revealed by their Globular Clusters

Low Surface Brightness {LSB} galaxies encompass many of the extremes
in galaxy properties. Their understanding is essential to complete our
picture of galaxy formation and evolution. Due to their historical
under-representation on galaxy surveys, their importance to many areas
of astronomy has only recently began to be realized. Globular clusters
are superb tracers of the formation histories of galaxies and have
been extensively used as such in high surface brightness galaxies. We
propose to investigate the nature of massive LSB galaxies by studying
their globular cluster systems. No globular cluster study has been
reported for LSB galaxies to date. Yet, both the presence or absence
of globular clusters set very strong constraints on the conditions
prevailing during LSB galaxy formation and evolution. Both in dwarf
and giant high surface brightness {HSB} galaxies, globular clusters
are known to form as a constant fraction of baryonic mass. Their
presence/absence immediately indicates similarities or discrepancies
in the formation and evolution conditions of LSB and HSB galaxies. In
particular, the presence/absence of metal-poor halo globular clusters
infers similarities/differences in the halo formation and assembly
processes of LSB vs. HSB galaxies, while the presence/absence of
metal-rich globular clusters can be used to derive the occurrence and
frequency of violent events {such as mergers} in the LSB galaxy
assembly history. Two band imaging with ACS will allow us to identify
the globular clusters {just resolved at the selected distance} and to
determine their metallicity {potentially their rough age}. The
composition of the systems will be compared to the extensive census
built up on HSB galaxies. Our representative sample of six LSB
galaxies {cz 2700 km/s} are selected such, that a large system of
globular clusters is expected. Globular clusters will constrain phases
of LSB galaxy formation and evolution that can currently not be probed
by other means. HST/ACS imaging is the only facility capable of
studying the globular cluster systems of LSB galaxies given their
distance and relative scarcity.

FGS 10610

Astrometric Masses of Extrasolar Planets and Brown Dwarfs

We propose observations with HST/FGS to estimate the astrometric
elements {perturbation orbit semi-major axis and inclination} of
extra-solar planets orbiting six stars. These companions were
originally detected by radial velocity techniques. We have
demonstrated that FGS astrometry of even a short segment of reflex
motion, when combined with extensive radial velocity information, can
yield useful inclination information {McArthur et al. 2004}, allowing
us to determine companion masses. Extrasolar planet masses assist in
two ongoing research frontiers. First, they provide useful boundary
conditions for models of planetary formation and evolution of
planetary systems. Second, knowing that a star in fact has a plantary
mass companion, increases the value of that system to future
extrasolar planet observation missions such as SIM PlanetQuest, TPF,
and GAIA.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)

HSTARS:

9933 - GSAcq (1,2,2) resulted in fine lock backup (1,0,1) on FGS-1 @
245/0413z Previous OBAD #1 results: -212.74, -488.23, 534.56, 754.57.
Previous OBAD #2 results: 1.87, -9.93, 1.48, 10.22.


COMPLETED OPS REQUEST:
17532-3 - Power off Gyro 4 after TGS Transition @ 244/2248z

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS Gsacq 10 10
FGS Reacq 4 4
OBAD with Maneuver 28 28

FAD from OBAD with No Maneuver - 8

SIGNIFICANT EVENTS:

Flash Report for Gyro 4 Power Off - September 1, 2005

Gyro 4 was turned off. Operations Request 17532-3 was executed at
244/22:47 with the gyro power off command sent at 22:47:29.


 




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