Status Report

NASA Hubble Space Telescope Daily Report # 3800

By SpaceRef Editor
February 19, 2005
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT       # 3800



ACS 10156

Saturn’s Auroral Energy Deposition Coordinated with Cassini UVIS

An in-depth study of Saturn’s magnetosphere and auroral processes has
begun in Jan. 2004 with coordinated HST images of Saturn’s aurora
while the approaching Cassini measures the solar wind. This program is
expected to establish the degree of solar wind control of Saturn’s
aurora. The beginning of the Cassini orbiter tour of the Saturn system
in July 2004 will offer new opportunities for collaborative science.
The energetics of Saturn’s auroral processes can best be studied via
low resolution UV spectra of the emissions and the auroral “color
ratio”. The geometry of the initial Cassini orbits provides the best
observing geometry for UVIS measurements of auroral energetics when it
is close to Saturn on the night side. Both the distributions of the
auroral emissions and the energy of the precipitating particles can be
measured simultaneously at conjugate points north and south. This
proposal is to conduct one such simultaneous observation, which will
demonstrate the potential for future cycles. We request 5 HST orbits
to observe a large fraction of one complete Saturn rotation at the
same time as Cassini UVIS.

ACS/HRC 10145

Physical parameters of the upper atmosphere of the extrasolar planet

Every 3.5 days, the transits of the gaseous planet orbiting HD209458
offer the unique opportunity to investigate the spectral features of
an extra-solar planetary atmosphere. Using HST, we first discovered
the extended upper atmosphere of HD209458b through the detection of a
15% HI Lyman alpha absorption. We concluded that the hydrogen must be
escaping the planet with a lower limit rate of 10^10 g/s {Vidal-Madjar
et al. 2003}. Additional observations, subsequently allowed to detect
OI and CII in the upper atmosphere implying that this atmosphere is
hydrodynamically escaping {in “blow off”, Vidal-Madjar et al. 2004}.
Here we propose to further study this upper atmosphere to better
constrain the “blow off” state by directly estimating the physical
conditions and the flow characteristics. In particular we will
determine the temperature and density at the base of the upper
atmosphere {the thermosphere}, and the density distribution and
ionization state just below that level. Comparison between the optical
and ultraviolet occultation light curves will provide useful
information on the molecular/haze content of the lower atmosphere. The
observation of six HD209458b transits with HRC and SBC settings will
allow the detection of many lines addressing these issues. The
proposed observations will give us for the first time a detailed probe
of the atmosphere of an “evaporating” extra-solar planet.With species
as abundant as FeII or MgII, the damping wings in the strongest lines
will start to form at levels around 1.9% absorption. Due to either the
strength of the MgII doublet lines around 280 nm or the packing of
FeII lines, strong absorptions arising from the accumulated damping
wings should show up clearly in FeII and MgII. All these signatures
should be easily detected even with the 40 to 100 Angstrom resolution
of the PR200L prism in these spectral regions. In addition to these
goals, any signature of molecules {e.g CO below 154 nm}, dust or haze
should also show up as broad band absorption in both PR110L and PR200L
settings. The estimate of the planet radius at different wavelengths
in the UV would become possible for all efficient absorbers in this
spectral range. The achievement of 0.1% precision in the occultation
curves thus provides sensitivity high enough to potentially lead to
important discoveries.


The Star Formation History and Metallicity Evolution of M33: A
Comprehensive Study of Disk Evolution

We will obtain deep, panchromatic imaging photometry of stellar
populations in four fields ranging from 0.5 to 4 scale lengths across
the disk of the Local Group spiral M33. The observations are designed
to detect the oldest main-sequence turnoffs in three outer disk
fields, and to reach the crowding limit in the innermost field. We
will combine the photometry data with information we already have
in-hand on abundances from stars and H II regions in M33 to derive the
star formation history and metallicity evolution of the M33 disk. The
information from our four fields will allow us to obtain {1} the ages
of the oldest disk stars and the radial variation of their ages; {2}
the radial variation of the star formation history and its nature
{e.g., constant, declining, or bursting}; and {3} the metallicity
distribution in each field and the time evolution of the metallicity
gradient. Our team, an experienced mix of photometrists,
spectroscopists, and galaxy evolution theorists, will use the results
from this program to construct a comprehensive chemo- dynamical model
for the M33 disk. This detailed study of M33 will be a key in
developing an understanding of the formation and evolution of disks
that can be applied to studies of disks at both low and high redshift,
and will also yield a wealth of information on stellar populations,
chemical evolution, and star clusters that will be of great value to
future investigators.

ACS/HRC/NIC2 10455

ACS Two-gyro Mode / Three-Gyro PSF Baseline Test

1 orbit. This test provides a three-gyro baseline for PSF measurements
planned in the February 2005 two-gyro test. Due to the recent re-focus
of the OTA, this test was thought to be advisable. The program is
essentially identical to program 10443 visit 1.

ACS/WFC 10152

A Snapshot Survey of a Complete Sample of X-ray Luminous Galaxy
Clusters from Redshift 0.3 to 0.7

We propose a public, uniform imaging survey of a well-studied,
complete, and homogeneous sample of X-ray clusters. The sample of 73
clusters spans the redshift range between 0.3-0.7. The samples spans
almost 2 orders of magnitude of X-ray luminosity, where half of the
sample has X-ray luminosities greater than 10^44 erg/s {0.5- 2.0 keV}.
These snapshots will be used to obtain a fair census of the morphology
of cluster galaxies in the cores of clusters, to detect radial and
tangential arc candidates, to detect optical jet candidates, and to
provide an approximate estimate of the shear signal of the clusters
themselves, and potentially an assessment of the contribution of large
scale structure to lensing shear.


Accurately Mapping M31’s Microlensing Population

We propose to augment an existing microlensing survey of M31 with
source identifications provided by a modest amount of ACS {and WFPC2
parallel} observations to yield an accurate measurement of the masses
responsible for microlensing in M31, and presumably much of its dark
matter. The main benefit of these data is the determination of the
physical {or “Einstein”} timescale of each microlensing event, rather
than an effective {“FWHM”} timescale, allowing masses to be determined
more than twice as accurately as without HST data. The Einstein
timescale is the ratio of the lensing cross-sectional radius and
relative velocities. Velocities are known from kinematics, and the
cross-section is directly proportional to the {unknown} lensing mass.
We cannot easily measure these quantities without knowing the
amplification, hence the baseline magnitude, which requires the
resolution of HST to find the source star. This makes a crucial
difference because M31 lens mass determinations can be more accurate
than those towards the Magellanic Clouds through our Galaxy’s halo
{for the same number of microlensing events} due to the better
constrained geometry in the M31 microlensing situation. Furthermore,
our larger survey, just completed, should yield at least 100 M31
microlensing events, more than any Magellanic survey. A small amount
of ACS+WFPC2 imaging will deliver the potential of this large database
{about 350 nights}. For the whole survey {and a delta-function mass
distribution} the mass error should approach only about 15%, or about
6% error in slope for a power-law distribution. These results will
better allow us to pinpoint the lens halo fraction, and the shape of
the halo lens spatial distribution, and allow
generalization/comparison of the nature of halo dark matter in spiral
galaxies. In addition, we will be able to establish the baseline
magnitude for about 50, 000 variable stars, as well as measure an
unprecedentedly detailed color-magnitude diagram and luminosity
function over much of M31.

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.


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

17366-0 – FSW 2.7A RAM Installation @ 048/1226z
17368-0 – Perform ESTR Reconditioning Prior to F2G On-Orbit Test @ 049/0050z


                             SCHEDULED     SUCCESSFUL    FAILURE TIMES 
 FGS Gsacq                   7                         7 
 FGS Reacq                   8                         8 
 FHST Update                 12                      12 


Flightsoftware (FSW) 2.7 Release A was successfully installed in
HST486 RAM (Ops Request 17366-0). The baseline RAM memory dump was
completed at 045/17:34:21. The 2.7A RAM loads were completed and the
2.7A flight software activated at 048/10:47:29. The post-installation
RAM memory dump was completed at 048/12:25:55 and verified by FSW.
Telemetry was monitored for 1 orbit following the 2.7A activation and
everything was nominal.

SpaceRef staff editor.