HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4501
PERIOD
COVERED: UT December 6, 2007 (DOY 340)
OBSERVATIONS
SCHEDULED
FGS
11211
An Astrometric
Calibration of Population II Distance Indicators
In
2002 HST produced a highly precise parallax for RR Lyrae. That
measurement
resulted in an absolute magnitude, M{V}= 0.61+/-0.11, a
useful
result, judged by the over ten refereed citations each year
since.
It is, however, unsatisfactory to have the direct,
parallax-based,
distance scale of Population II variables based on a
single
star. We propose, therefore, to obtain the parallaxes of four
additional
RR Lyrae stars and two Population II Cepheids, or
stars.
The Population II Cepheids lie with the RR Lyrae stars on a
common
K-band Period-Luminosity relation. Using these parallaxes to
inform
that relationship, we anticipate a zero-point error of 0.04
magnitude.
This result should greatly strengthen confidence in the
Population
II distance scale and increase our understanding of RR Lyrae
star
and Pop II Cepheid astrophysics.
WFPC2
11002
A
Census of LIRGs in Clusters of Galaxies in the First Half of the
Universe
from the IRAC Shallow Survey
The
incidence of LIRGs and ULIRGs is roughly two orders of magnitude
higher
in the field at redshift z > 1, and at these redshifts such
objects
dominate the global star formation activity. Mergers which fuel
such
activity might be expected to enhance the frequency of LIRGs in
dense
environments. We propose to use MIPS to obtain a census of LIRGs
in
z > 1 galaxy clusters from a well defined sample found in the IRAC
Shallow
Survey. Supporting IRAC and HST ACS data are also requested.
WFPC2
11032
CTE
Extended Targets Closeout
Measuring
the charge transfer efficiency {CTE} of an astronomical CCD
camera
is crucial to determining the CCD's photometric fidelity across
the
field of view. WFPC2's CTE has degraded steadily over the last 13
years
because of continuous exposure to trapped particles in HST's
radiation
environment. The fraction of photometric signal lost from
WFPC2's
CTI {change transfer inefficiency} is a function of WFPC2's time
in
orbit, the integrated signal in the image, the location of the image
on
the CCD, and the background signal. Routine monitoring of WFPC2's
degrading
CTE over the last 13 years has primarily concerned the effects
of
CTI on point-source photometry. However, most of the sources imaged
by
WFPC2 are extended rather than point-like. This program aims to
characterize
the effects of CTI on the photometry and morphology of
extended
sources near the end of WFPC2's functional life. Images of a
standard
field within the rich galaxy cluster Abell 1689 are recorded
with
each WFPC2 camera using the F606W and F814W filters. These images
will
be compared with contemporaneous images of Abell 1689 recorded with
the
field rotated by approximately 180 degrees to assess differences
between
extended sources imaged near and far from the serial register.
The
images will also be compared with similar images recorded in Cycle 8
{Program
8456} to characterize the rate of CTE degradation over the
lifetime
of WFPC2.
WFPC2
11169
Collisions
in the Kuiper belt
For
most of the 15 year history of observations of Kuiper belt objects,
it
has been speculated that impacts must have played a major role in
shaping
the physical and chemical characteristics of these objects, yet
little
direct evidence of the effects of such impacts has been seen. The
past
18 months, however, have seen an explosion of major new discoveries
giving
some of the first insights into the influence of this critical
process.
From a diversity of observations we have been led to the
hypotheses
that: {1} satellite- forming impacts must have been common in
the
Kuiper belt; {2} such impacts led to significant chemical
modification;
and {3} the outcomes of these impacts are sufficiently
predictable
that we can now find and study these impact-derived systems
by
the chemical and physical attributes of both the satellites and the
primaries.
If our picture is correct, we now have in hand for the first
time
a set of incredibly powerful tools to study the frequency and
outcome
of collisions in the outer solar system. Here we propose three
linked
projects that would answer questions critical to the multiple
prongs
of our hypothesis. In these projects we will study the chemical
effects
of collisions through spectrophotometric observations of
collisionally
formed satellites and through the search for additional
satellites
around primaries with potential impact signatures, and we
will
study the physical effects of impacts through the examination of
tidal
evolution in proposed impact systems. The intensive HST program
that
we propose here will allow us to fully test our new hypotheses and
will
provide the ability to obtain the first extensive insights into
outer
solar system impact processes.
WFPC2
11178
Probing
Solar System History with Orbits, Masses, and Colors of
Transneptunian
Binaries
The
recent discovery of numerous transneptunian binaries {TNBs} opens a
window
into dynamical conditions in the protoplanetary disk where they
formed
as well as the history of subsequent events which sculpted the
outer
Solar System and emplaced them onto their present day heliocentric
orbits.
To date, at least 47 TNBs have been discovered, but only about a
dozen
have had their mutual orbits and separate colors determined,
frustrating
their use to investigate numerous important scientific
questions.
The current shortage of data especially cripples scientific
investigations
requiring statistical comparisons among the ensemble
characteristics.
We propose to obtain sufficient astrometry and
photometry
of 23 TNBs to compute their mutual orbits and system masses
and
to determine separate primary and secondary colors, roughly tripling
the
sample for which this information is known, as well as extending it
to
include systems of two near-equal size bodies. To make the most
efficient
possible use of HST, we will use a
optimally
schedule our observations.
WFPC2
11312
The
Local Cluster Substructure Survey {LoCuSS}: Deep Strong Lensing
Observations
with WFPC2
LoCuSS
is a systematic and detailed investigation of the mass,
substructure,
and thermodynamics of 100 X-ray luminous galaxy clusters
at
0.15<z<0.3. The primary goal is to test our recent suggestion that
this
population is dominated by dynamically immature disturbed clusters,
and
that the observed mass-temperature relation suffers strong
structural
segregation. If confirmed, this would represent a paradigm
shift
in our observational understanding of clusters, that were hitherto
believed
to be dominated by mature, undisturbed systems. We propose to
complete
our successful Cycle 15 program {SNAP:10881} which prior to
premature
termination had delivered robust weak-lensing detections in 17
clusters,
and candidate strongly-lensed arcs in 11 of these 17. These
strong
and weak lensing signals will give an accurate measure of the
total
mass and structure of the dark matter distribution that we will
subsequently
compare with X-ray and Sunyaev Zeldovich Effect
observables.
The broader applications of our project include 1} the
calibration
of mass-temperature and mass-SZE scaling relations which
will
be critical for the calibration of proposed dark energy
experiments,
and 2} the low redshift baseline study of the demographics
of
massive clusters to aid interpretation of future high redshift {z>1}
cluster
samples. To complete the all-important high resolution imaging
component
of our survey, we request deep WFPC2 observations of 20
clusters
through the F606W filter, for which wide-field weak-lensing
data
are already available from our Subaru imaging program. The
combination
of deep WFPC2 and Subaru data for these 20 clusters will
enable
us to achieve the science program approved by the Cycle 15 TAC.
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
11087
- GSAcq(1,2,2) requires multiple attempts to achieve CT-DV
OTA SE review of PTAS processing revealed that GSAcq(1,2,2) on day
333/04:07:32z required two attempts to achieve CT-DV on FGS1. The
acquisition was successful.
11090
- REACQ(2,3,2) fine lock backup on FGS 2
REACQ(2,3,2) at 340/02:18:31 acquired in fine lock backup on FGS 2
only,
with QF3STOPF and QSTOP flags set on FGS 3 at 02:22:50. No other
flags
were seen. Previous acquisitions at 339/21:31:59, 23:06:44 and
340/00:42:37 were successful
COMPLETED
OPS REQUEST:
18160-1
- Null genslews for proposal 11226 - slots 1-12
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSacq
06
06
FGS
REacq
08
08
OBAD
with Maneuver
30
30
SIGNIFICANT
EVENTS: (None)