Status Report

NASA Hubble Space Telescope Daily Report # 3870

By SpaceRef Editor
June 2, 2005
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT    # 3870



ACS/HRC 9854

Anomalous Flux Ratios in Quadruple Gravitationally Lensed QSOs

We propose to observe eight {8} gravitationally lensed systems which
exhibit quadruple images of the background high redshift quasars.
Models invoking a smooth potential fit the observed image positions
accurately, in most cases better than 5 milliarcseconds. But the same
models dramatically fail to predict the observed flux ratios. These
anomalous flux ratios can be attributed to micro- or milli-lensing in
the massive lensing halo. In this proposal, we will isolate the source
of the anomalous flux ratios by using the superior resolution of HST
to obtain spectrophotometric data and compare the emission line flux
ratio of the QSOs to the continuum flux ratios. Due to the much larger
size of the broad emission line regions, the flux ratios in the
emission lines should only be affected by milli-lensing if the
sub-halos are comparable or larger in projected size than the source
region. That is, flux ratios observed in the QSO continuum are
senstive to substructure on all scales {both micro- and
milli-lensing}, while the broad emission lines are insensitive to
micro-lensing due to the larger physical size of the source emission
region. This sample of eight quasars will provide the definitive
evidence to distinguish between possible sources causing the observed
anomalous flux ratios.


NICMOS Post-SAA calibration – CR Persistence Part 1.

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.

S/C 10700

Guide Star Test for the Deep Impact Encounter

This proposal is to perform guide star tests on the critical HST
science visits circum- encounter of the Deep Impact mission with comet
9P/Tempel 1.


The Late Formation of Satellite Galaxies

Tiny isolated HII regions have been discovered up to 30 kpc from the
closest galaxy in the NOAO Survey for Ionization in Neutral Gas
Galaxies {SINGG}. These halo HII regions can be ionized by only a few
OB stars and seem to be most commonly found in interacting systems.
They may represent the beginning of the formation of satellite
galaxies at low redshift and/or are the source of the numerous
intracluster planetary nebula. The halo HII regions are a unique mode
of star formation in a low density and low metallicity environment and
high resolution HST images are required to identify their underlying
stellar populations. Determining the stellar populations of these HII
regions will establish whether in-situ star formation is a significant
contributor to the stellar content and enrichment of galactic halos
and intergalactic space. In particular, ACS/HRC observations are
required for their resolution, UV sensitivity, and wide wavelength
coverage, allowing young and intermediate age populations to be
identified. Parallel ACS/WFC observations will explore the possibility
of a further stellar population in the interactive debris. The results
of this project have implications on the formation of satellite
galaxies, the origin of Galactic halo B stars, IGM ionization and
enrichment, and star formation principles.

ACS/HRC 10431

A Search for Faint Companions of Altair

We propose to use the innovative new technique of spectral
deconvolution {Sparks & Ford 2002} to search for very faint
companions, possibly extrasolar planets shining by reflected light,
around Altair, the nearest bright, single star to the Sun. The
technique offers a Poisson-limited detection capability that brings
Jovian-class planets into the realm of feasibility for a select few
stars. We turn the wavelength dependence of the coronagraphic PSF to
advantage and use it to eliminate stray light from the host star. As
part of the detection process, we obtain a spectrum over the
wavelength range, 750 nm to 1 micron, with 9% resolution. The search
will be orders of magnitude more sensitive than all previous efforts
and should take us to within about an order of magnitude of the Jovian
luminosity flux limit.


The Formation and Evolution of Spirals: An ACS and WFPC2 Imaging
Survey of Nearby Galaxies

Over 50% of galaxies in the local universe are spirals. Yet the star
formation histories and evolution of this crucial population remain
poorly understood. We propose to combine archival data with new
ACS/WFC and WFPC2 observations of 11 galaxies, to tackle a
comprehensive investigation of nearby spirals covering the entire
spiral sequence. The new observations will fill a serious deficiency
in HST’s legacy, and maximize the scientific return of existing HST
data. The filter combination of UBVI, and Halpha is ideal for studying
stellar populations, dust properties, and the ISM. Our immediate
scientific objectives are: {i} to use the resolved cluster
populations, both young massive clusters and ancient globular clusters
as a chronometer, to understand how spirals assembled as a function of
time; {ii} study the rapid disruption properties of young clusters;
and {iii} understand dust distributions in spirals from pc to kpc
scales. Each of these goals provides an important step towards
charting the evolution of galaxies, and an essential baseline for
interpreting the galaxy populations being surveyed in both the early
and present universe. The resolution of our survey, which exploits the
excellent imaging capabilities of HST’s two optical cameras, will
enable us to understand the record of star cluster, and galaxy
formation in a level of detail which is not possible for more distant
systems. Finally, the proposed observations will provide a key to
interpret an extensive, multiwavelength archive of space- and ground-
based data at lower spatial resolution {SPITZER, CHANDRA, GALEX,
NICMOS P alpha and H band imaging} for local spirals.


Accurate and Robust Calibration of the Extragalactic Distance Scale
with the Maser Galaxy NGC4258 II

The extragalactic distance scale {EDS} is defined by a comparison of
Cepheid Period-Luminosity {PL} relations for nearby galaxies and the
LMC, whose uncertain distance is thereby the SOLE anchor. Studies of
masers orbiting the central black hole in NGC4258 have provided the
most accurate extragalactic distance ever {7.2+/-0.5 Mpc}, and new
radio data and analysis techniques will reduce the uncertainty to < 3.5% {0.07 mag} by 2005. Since this distance is well determined and based on geometric arguments, NGC4258 can provide a much needed new anchor for the EDS. Ultimately, the combination of an independent measurement of H0 and measurements of CMB fluctuations {e.g., WMAP} can be used to directly constrain cosmological parameters including the equation of state of dark energy. In our Cycle 12 proposal, we defined a program spanning two cycles. The Cycle 12 portion was accepted. We have acquired WFC images and are constructing well sampled PL relations in 3 colors {BVI}. The purpose of the Cycle 13 observations is to address systematic sources of error and is crucial for the success of the entire program. To disentangle the effects of reddening and metallicity, and to characterize the effects of blending, we require 50 orbits to obtain H-band photometry {NICMOS/NIC2} and high resolution images {ACS/HRC}.


The Ghosts of Galaxies: Tidal Debris and the Formation of Clusters

Intergalactic stellar populations and tidal debris are now recognized
as important components of galaxy clusters. This project examines the
interrelated processes of galaxy destruction, recycling of tidal
debris, and creation of dwarf galaxies and intergalactic star
clusters, all of which are part of the grand scheme of cluster
formation. We propose deep multicolor imaging of two examples of newly
created tidal debris, the spectacular plumes in the Centaurus and Coma
clusters. The Centaurus observations will extend our earlier work,
which demonstrated the existence of tidal debris dwarf galaxies and
star cluster in the body of the Centaurus plume. Deep ACS/WFC
observations can determine rough ages and cluster membership, better
characterizing the new debris. The Coma observations will reproduce
this work for a second plume feature, in the quintessential rich
cluster of galaxies. Parallel WFPC2 observations will investigate the
central intracluster spaces at the bottom of the each cluster’s
potential, where older debris is thickest.


Deep imaging of newly discovered globular clusters in the outer halo
of M31

Globular clusters {GCs} are fossil relics with which we can
investigate the processes of galaxy formation and growth. We have
recently discovered a sample of GCs, as part of a very wide area CCD
survey of M31. These clusters span a range in projected galactocentric
distance of 20 – 80 kpc, more than double the radii of the previous
most remote known GC. Here we apply for deep ACS images of 13 GCs,
which will allow us to study their stellar populations, line-of-sight
distances and structural parameters. These will be used to: a}
Investigate the merger history of M31, through an examination of
variations in the RGB and HB morphologies, particularly to obtain
metallicities and check for the presence of any second parameter
effect in the HB. d} Determine, in conjuction with ground-based
spectroscopy, the dynamical mass of M31 at large radius, providing a
direct probe of the mass distribution of its dark halo.


ACS CCDs daily monitor – Cycle 13 – Part 2

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.


Focus Monitor

The focus of HST is measured from WFPC2/PC and ACS/HRC images of
stars. Multiple exposures are taken in parallel over an orbit to
determine the influence of breathing on the derived mean focus.
Observations are taken of clusters with suitable orientations to
ensure stars appear in all fields.

ACS/HRC 10377

ACS Earth Flats

High signal sky flats will be obtained by observing the bright Earth
with the HRC and WFC. These observations will be used to verify the
accuracy of the flats currently used by the pipeline and will provide
a comparison with flats derived via other techniques: L-flats from
stellar observations, sky flats from stacked GO observations, and
internal flats using the calibration lamps. Weekly coronagraphic
monitoring is required to assess the changing position of the spots.

WFPC2 10363

WFPC2 CYCLE 13 Intflat and Visflat Sweeps and Filter Rotation Anomaly

Using intflat observations, this WFPC2 proposal is designed to monitor
the pixel-to- pixel flatfield response and provide a linearity check.
The intflat sequences, to be done once during the year, are similar to
those from the Cycle 12 program 10075. The images will provide a
backup database as well as allow monitoring of the gain ratios. The
sweep is a complete set of internal flats, cycling through both
shutter blades and both gains. The linearity test consists of a series
of intflats in F555W, in each gain and each shutter. As in Cycle 12,
we plan to continue to take extra visflat, intflat, and earthflat
exposures to test the repeatability of filter wheel motions.

ACS/WFC 10352

A Study of the Physics of Extended Relativistic X-ray Jets, Discovered
in our

We will measure the changing flow speeds, magnetic fields, and energy
fluxes in well-resolved quasar jets found in our short-exposure
Chandra survey by combining new, deep Chandra data with radio and
optical imaging. We will image each jet with sufficient sensitivity to
estimate beaming factors and magnetic fields in several distinct
regions, and so map the variations in these parameters down the jets.
HST observations will help diagnose the role of synchrotron emission
in the overall SED, and may reveal condensations on scales less than
0.1 arcsec.

ACS/WFC 10343

X-ray from misaligned FRI jets: IC/CMB emission from a fast spine?

There is evidence that FRI jets have a fast “spine”, consisting of
relativistically moving plasma, and a slow “wall”, decelerated by
entrainement of ambient gas. This opens the interesting possibility
that inverse Compton scattering of the CMB photons {IC/CMB} off the
relativistic electrons could contribute to the high-energy emission
from the fast spine. This strongly beamed radiation is visibile only
in closely aligned FRI jets, i.e., acccording to unification schemes,
in BL Lac objects. Thus, we propose to observe 2 radio-selected BL
Lacs with prominent radio jets to search for IC/CMB X-ray emission and
confirm unification models. This study will impact models for the
origin of the FRI/II division.

ACS/HRC 10255

A Never Before Explored Phase Space: Resolving Close White Dwarf / Red

We propose an ACS Snapshot imaging survey to resolve a well-defined
sample of highly probable white dwarf plus red dwarf close binaries.
These candidates were selected from a search for white dwarfs with
infrared excess from the 2MASS database. They represent unresolved
systems {separations less than approximately 2″ in the 2MASS images}
and are distributed over the whole sky. Our HST+ACS observations will
be sensitive to a separation range {1-20 AU} never before probed by
any means. The proposed study will be the first empirical test of
binary star parameters in the post-AGB phase, and cannot be
accomplished from the ground. By resolving as few as 20 of our ~100
targets with HST, we will be able to characterize the distribution of
orbital semi-major axes and secondary star masses.

ACS/SBC 10231

Tracing the Reionization History of Intergalactic Helium out to
Redshift 3.8

We have found He II absorption in a quasar at redshift 3.82 via our
Cycle 12 program of UV snapshots. This is the highest redshift yet at
which He II absorption has been observed, and we propose to study
helium ionization in the IGM along this new, long, unobscured
sightline to high- redshift. The object has UV flux comparable to that
of the rare handful of other z>3 quasars known to be suitable for
helium studies, and it is also in the Continuous Viewing Zone.
Theproposed spectrum will allow us to study the evolution and
properties of the IGM and ionizing radiation from z=3.8 {the IGM
environment near the quasar} all the way down to z=2.8. This redshift
range may span the epoch of helium reionization, and even extends to
high enough redshift to enable improved helium opacity measures using
both He II Ly-alpha and Ly-beta. This program is now approved to use
ACS prism.

ACS/HRC 10198

Probing the Dynamics of the Galactic Bar through the Kinematics of

The observed optical depths to microlensing of stars in the Galactic
bulge are difficult to reconcile with our present understanding of
Galactic dynamics. The main source of uncertainty in those comparisons
is now shifting from microlensing measurements to the dynamical models
of the Galactic bar. We propose to constrain the Galactic bar models
with proper motion observations of Bulge stars that underwent
microlensing by determining both the kinematic identity of the
microlensed sources and the importance of streaming motions. The
lensed stars are typically farther than randomly selected stars.
Therefore, our proper motion determinations for 36 targeted MACHO
events will provide valuable constraints on the dynamics of bulge
stars as a function of distance. The first epoch data for our proposed
events is already available in the HST archive so the project can be
completed within a single HST cycle. The exceptional spatial
resolution of HST is essential for completion of the project.
Constraints on the total mass in the bulge will ultimately lead to the
determination of the amount of dark matter in inner Galaxy.

ACS/WFC/NIC3 10195

Probing the Surroundings of a Highly Luminous Redshift 6.5 Galaxy

We propose deep images of a recently discovered galaxy at z=6.535,
which is among the most luminous Lyman-alpha emitting galaxies known
at high redshift. The brightness and rarity of this source imply that
it is associated with a high peak in the matter density distribution.
{It is the brightest Lyman alpha source in 2e5 comoving Mpc3, with a
luminosity of 6 L*.} Further objects in this peak are expected to be
visible with HST’s sensitivity. The Lyman alpha line has a large rest
frame equivalent width, with a lower bound >100 Angstroms. Such a
large equivalent width would be impossible for objects embedded in
neutral gas, and instead requires either that {a} the universe was
reionized before z=6.5 or {b} the galaxy resides in a local ionized
bubble, in which case an additional contribution to the ionizing
photon budget from presently undetected neighbors is required. With 19
orbits of ACS and NICMOS imaging, we will measure this object’s
morphology and spectral energy distribution, thus searching for either
active nuclei or old stellar populations. We will also search for
possible neighbors, which could establish the first known galaxy group
at z>6, and may provide sufficient ionizing flux to allow the escape
of the observed Lyman alpha photons in a neutral universe. If
neighbors are not found, it will lead to an upper bound on the neutral
fraction in the general IGM at z=6.5.

ACS/HRC 10185

When does Bipolarity Impose itself on the Extreme Mass Outflows from
AGB Stars? An ACS SNAPshot Survey

Essentially all well-characterized preplanetary nebulae {PPNe} —
objects in transition between the AGB and planetary nebula
evolutionary phases – are bipolar, whereas the mass-loss envelopes of
AGB stars are strikingly spherical. In order to understand the
processes leading to bipolar mass-ejection, we need to know at what
stage of stellar evolution does bipolarity in the mass-loss first
manifest itself? Our previous SNAPshot surveys of a PPNe sample {with
ACS & NICMOS} show that roughly half our targets observed are
resolved, with well-defined bipolar or multipolar morphologies.
Spectroscopic surveys of our sample confirm that these objects have
not yet evolved into planetary nebulae. Thus, the transformation from
spherical to aspherical geometries has already fully developed by the
time these dying stars have become preplanetary nebulae. From this new
and surprising result, we hypothesize that the transformation to
bipolarity begins during the very late AGB phase, and happens very
quickly, just before, or as the stars are evolving off the AGB. We
propose to test this hypothesis quantitatively, through a SNAPshot
imaging survey of very evolved AGB stars which we believe are nascent
preplanetary nebulae; with our target list being drawn from published
lists of AGB stars with detected heavy mass-loss {from millimeter-wave
observations}. This survey is crucial for determining how and when the
bipolar geometry asserts itself. Supporting kinematic observations
using long-slit optical spectroscopy {with the Keck}, millimeter and
radio interferometric observations {with OVRO, VLA & VLBA} are being
undertaken. The results from this survey {together with our previous
work} will allow us to draw general conclusions about the onset of
bipolar mass-ejection during late stellar evolution, and will provide
crucial input for theories of post-AGB stellar evolution. Our survey
will produce an archival legacy of long-standing value for future
studies of dying stars.

NIC2 10176

Coronagraphic Survey for Giant Planets Around Nearby Young Stars

A systematic imaging search for extra-solar Jovian planets is now
possible thanks to recent progress in identifying “young stars near
Earth”. For most of the proposed young {<~ 30 Myrs} and nearby {<~ 60 pc} targets, we can detect a few Jupiter-mass planets as close as a few tens of AUs from the primary stars. This represents the first time that potential analogs of our solar system - that is planetary systems with giant planets having semi-major axes comparable to those of the four giant planets of the Solar System - come within the grasp of existing instrumentation. Our proposed targets have not been observed for planets with the Hubble Space Telescope previously. Considering the very successful earlier NICMOS observations of low mass brown dwarfs and planetary disks among members of the TW Hydrae Association, a fair fraction of our targets should also turn out to posses low mass brown dwarfs, giant planets, or dusty planetary disks because our targets are similar to {or even better than} the TW Hydrae stars in terms of youth and proximity to Earth. Should HST time be awarded and planetary mass candidates be found, proper motion follow-up of candidate planets will be done with ground-based AOs.

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 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.

NIC3 10150

NICMOS observations of A1689

The potential of galaxy clusters as “cosmic telescopes” has been
known for a long time, but practical results in the pre-ACS era have
been scarce due to two main problems: the uncertainty in determining
the magnification distribution of the cluster {the “optics” of the
instrument} and the presence of numerous bright cluster galaxies which
cover the field of view and hinder the detection of background
galaxies. We have developed techniques to solve these two problems
working with our ACS observations of A1689, the most powerful lens in
the sky, and for the first time we have been able to determine the
“specifications” of a cosmic telescope with a useful level of
precision, thanks to the detection and identification of more than 100
multiple images with reliable redshift information. We propose to
observe the high magnification region in the A1689 field in the F110W
band with a 3×3 mosaic of NIC3 pointings; the resulting image will
reach a lens-corrected limiting magnitudes of 29.5 for point sources,
surpassing in depth the UDF NICMOS observations and providing an
unique dataset with multiple scientific returns.


Determining the Origin of Virgo’s Intracluster Stars

Intracluster stars constitute about 20% of the total stellar
population of a typical galaxy cluster, and their existence provides a
vital clue for our understanding of cluster formation and evolution.
However, to exploit their probative value, we need to know their
origins: are they the remnants of dwarf galaxies, long since destroyed
by the cluster potential, or have the stars been harassed from their
parent galaxies at recent epochs? To answer this question, we propose
to use the Wide-Field Channel of ACS to make an I, {V-I}
color-magnitude diagram of Virgo’s intracluster stars. From the
position and morphology of the population’s red giant branch, we will
be able to determine the metallicity distribution function of the
stars, and thereby determine their likely origin and ejection
mechanisms. Only HST with the ACS has the sensitivity and resolution
to perform this fundamental measurement. This program has two options.
Option one uses conventional methods of cluster photometry and
requires 37 orbits of exposure time. Option two involves a novel
analysis technique, which promises to achieve most of the same science
in two- thirds the time {23 orbits}. We describe this alternative
method of analysis and demonstrate its use via simulations.

ACS/WFC 10119

Solving the Mystery of the Short-Hard Gamma-Ray Bursts

Seven years after the afterglow detections that revolutionized studies
of the long- soft gamma-ray bursts, not even one afterglow of a
short-hard GRB has been seen, and the nature of these events has
become one of the most important problems in GRB research. The
forthcoming Swift satellite will report few-arcsecond localizations
for short-hard bursts in minutes, however, enabling prompt, deep
optical afterglow searches for the first time. Discovery and
observation of the first short-hard optical afterglows will answer
most of the critical questions about these events: What are their
distances and energies? Do they occur in distant galaxies, and if so,
in which regions of those galaxies? Are they the result of collimated
or quasi-spherical explosions? In combination with an extensive
rapid-response ground-based campaign, we propose to make the critical
high-sensitivity HST TOO observations that will allow us to answer
these questions. If theorists are correct in attributing the
short-hard bursts to binary neutron star coalescence events, then the
short-hard bursts are signposts to the primary targeted source
population for ground- based gravitational-wave detectors, and
short-hard burst studies will have a vital role to play in guiding
their observations.

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.

ACS/HRC 10102

Rings of Uranus: Dynamics, Particle Properties and Shepherding Moons

Last year, our Uranian ring and moon observing program {GO-9823}
resulted in the discovery of two moons, S/2003 U 1 and S/2003 U 2. We
imaged two additional small moons, Ophelia and S/1986 U 10, that had
not been seen since the Voyager encounter of 1986. Furthermore, our
data show faint arcs and clumps orbiting within the rings, which were
not seen by Voyager and are completely unexpected. We employed several
“tricks” of the HRC to achieve this remarkable sensitivity;
specifically, we used the CLEAR filter and oriented the images so that
the planet, though vastly overexposed, did not interfere with the
ring/moon region of interest to us. This allowed us to detect
25th-magnitude moons circling a 5th-magnitude planet. Now we propose
to complete the task by carrying out a comprehensive survey of the
system using the same techniques. Our goals are to recover the moons,
better discern their orbital elements, and learn more about the
dynamics of the ring clumps. In particular, we need to {1} understand
the long-term stability of S/2003 U 2, which orbits perilously close
to the larger moon Belinda; {2} complete our search for moons, which
was only ~ 50% complete last year, and {3} better understand how the
clumps and arcs within the ring system might relate to nearby
“shepherding” moons, seen or unseen. This program is now a merger of
two programs 10275 and 10102. The former is our new program, whereas
the latter is the second year of our three-year program to study the
light scattering properties of Uranus’s rings as they approach their
edge-on presentation in 2007.


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


9836 – GSacq(2,1,2) Failed to RGA control @ 149/18:03:59z The
GSacq(2,1,2) scheduled at 149/17:54:18 failed to RGA control due to
search radius limit exceeded on FGS 1 and FGS 2. the following Reacqs
also failed due to SRLEX. A real time map at 20:35 showed errors of
-10.781, 39.085, and 7.170 .

9837 – ACS Target Acquistion Failed Due to Guide Star Failure. @
149/18:09:33z ACS target acquisition scheduled at 149/18:07:50 failed
due to GSacq failure. ACS Status Buff message 954, P= 1, T = 13745



 FGS Gsacq          34             33        Hstar # 9836 
 FGS Reacq          28             25        Hstar # 9836 
 FHST Update        57             57 


SpaceRef staff editor.