Notice: For the foreseeable future, the daily reports may
contain
apparent discrepancies between some proposal descriptions
and the listed
instrument usage. This is due to the conversion of
previously approved
ACS WFC or HRC observations into WFPC2, or NICMOS
observations
subsequent to the loss of ACS CCD science capability in
late January.
HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT # 4358
PERIOD COVERED: UT May 08, 2007 (DOY 128)
OBSERVATIONS SCHEDULED
WFPC2 10800
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 to
continue a Snapshot program using the ACS/HRC that has a
demonstrated
discovery potential an order of magnitude higher than the
HST
observations that have already discovered the majority of
known
transneptunian binaries. With this continuation we seek to
reach the
original goals of this project: to accumulate a
sufficiently large
sample in each of the distinct populations collected in
the Kuiper Belt
to be able to measure, with statistical significance, how
the fraction
of binaries varies as a function 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.
WFPC2 10832
Solving the microlensing puzzle: An HST high-resolution
imaging approach
We propose to use the HST Advanced Camera for Surveys High
Resolution
Channel to obtain high resolution imaging data for 10
bona-fide LMC
microlensing events seen in the original MACHO survey. The
purpose of
this survey will be to assess whether or not the lens and
source stars
have separated enough to be resolved since the original
microlensing
event took place - about a decade has passed since the
original MACHO
survey and the HST WFPC2 follow-up observations of the
microlensing
events. If the components of the lensing event are
resolved, we will
determine the apparent magnitude and color of both the
lens and the
source stars. These data, in combination with Spitzer/IRAC
data and
Magellan near-IR JHK data, will be used to ascertain the
basic
properties of the lens stars. With the majority of the
microlensing
events in the original MACHO survey observed at the
highest spatial
resolution currently possible, we will be able to draw
important
conclusions as to what fraction of these events have
lenses which belong
to some population of dwarf stars in the disk and what
fraction must be
due to lenses in the halo or beyond. These data will greatly
increase
our understanding of the structure of the Galaxy by
characterizing the
stellar population responsible for the gravitational
microlensing.
WFPC2 10788
Probing the Central Dark Mass Concentration of the
Collapsed-Core
Globular Cluster M15
We plan to probe the central dark mass concentration in
the
collapsed-core globular cluster M15 by analyzing the
structure of its
central stellar cusp with the highest possible angular
resolution. The
rapid rise of M/L toward the center of M15 can be alternatively
explained by a central concentration of several thousand
compact
remnants {heavy white dwarfs and neutron stars} or instead
by the
presence of an intermediate-mass black hole {IMBH} of a
few thousand
solar masses. We propose to obtain one orbit of highly
dithered WFPC2
F555W {V} imaging to supplement the available ACS/HRC
F435W {B} imaging
from GO-10401. This will allow us {1} to improve the
constraints on the
radius of the as yet unresolved core and {2} to
investigate the relation
between cusp slope and stellar mass, the form of which
depends on the
size and mix of the remnant population and on whether or
not an IMBH is
present. We will compare the central cusp structure with
predictions
from both Fokker-Planck and GRAPE-6 N-body models, with
and without
IMBHs, to constrain the nature of the intriguing dark mass
concentration.
WFPC2 10791
Proper motion may nail counterpart of unique X-ray pulsar
1E 1207.4-5209 is one of the most puzzling X-ray compact
sources in the
Galaxy. Long known to be a radio-quiet Neutron Star {NS}
embedded in a
young {~7000 y} supernova remnant, it displays a unique
phenomenology,
including multiple cyclotron absorption features in its
thermal X-ray
spectrum, as well as a possible non-monotonous evolution
of its 424 ms
rotational period. A candidate optical counterpart
{I~23.4} with very
red colours {not consistent with the expected emission of
a NS, but
rather with a low-mass stellar companion, or a fossil
disk} was singled
out with HST/ACS in 2003, at the margin of the Chandra
error box. In
order to test the reality of such an association, we
propose to take
advantage of the high space velocities characteristics of
NSs to search
for the expected displacement {~150 mas in the NE
direction} of the
candidate counterpart over a 3 years time span. One orbit
observation,
either unveiling the displacement or ruling it out, will
settle the
problem of the optical identification of 1E1207.4-5209. We
stress that a
null result would also be important for the understanding
of this
source.
WFPC2 10823
The spectrum of a magnetar in the blue and ultraviolet.
Magnetars are natural laboratories for investigating the
behaviour of
matter at the very extremes of nature. The magnetar CXOU
J010043.1-721134 was serendipitously discovered by WFPC2
imaging of the
SMC. Because of the low reddening to this source compared
to the other
magnetars, this is a unique opportunity to measure the
spectral shape in
the blue and ultraviolet. We hope also to establish the
feasibility of
spectroscopic follow-up. We are asking for two orbits of
ACS imaging.
WFPC2 10903
Resolving the LMC Microlensing Puzzle: Where are the
Lensing Objects?
We are requesting 12 HST orbits to continue to investigate
the nature of
the population that gives rise to the microlensing seen
towards the LMC.
This proposal builds on the cycle 14 HST program {10583}
and will
complement the study with 12 yet-to-be discovered
microlensing
candidates from Fall 2006. Our SuperMacho project is an
ongoing ground-
based survey on the CTIO 4m that has demonstrated the
ability to detect
LMC microlensing events via frame subtraction. The
combination of high
angular resolution and photometric accuracy with HST will
allow us to 1}
confrim that the detected flux excursions arise from LMC
stars, rather
than background supernovae or AGN, and 2} obtain reliable
baseline flux
measurements for the objects in their unlensed state. This
latter
measurement in important in determining the microlensing
optical depth
towards the LMC.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are
preliminary reports
of potential non-nominal performance that will be
investigated.)
HSTARS: (None)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS GSacq
05
05
FGS REacq
08
08
OBAD with Maneuver
26
26
SIGNIFICANT EVENTS:
Evaluation of Universal Kalman Filter performance
continued. Details
follow.
Background Kalman Filter Operation Flash Report for day
127
The KF was halted at 127/18:15. The filter was restarted
at 127/18:18
with the CSS disabled, the Gyro2 input enabled, during
orbit day, during
a vehicle slew and during an M2G guiding interval and
during a slow
changing B-field. All UKF parameters showed nominal
operation. The test
was an MSS/Gyro2 Initialization test case during a vehicle
slew with a
slow changing B-field (M_G2_IVS, Test #35).
The KF was reconfigured and restarted at 127/19:14 with
the CSS and both
gyro inputs disabled to leave the filter in an MSS only
configuration.
This configuration is to help provide a earlier baseline
set of data for
PCS analysis and it will remain the default configuration
outside of
other KF convergence testing for the remainder of the week.