Notice:
Due to the conversion of some ACS WFC or HRC observations into
WFPC2,
or NICMOS observations after the loss of ACS CCD science
capability
in January, there may be an occasional discrepancy between a
proposal's
listed (and correct) instrument usage and the abstract that
follows
it.
HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4441
PERIOD
COVERED: UT September 05, 2007 (DOY 248)
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 W Vir
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.
FGS
11212
Filling
the Period Gap for Massive Binaries
The
current census of binaries among the massive O-type stars is
seriously
incomplete for systems in the period range from years to
millennia
because the radial velocity variations are too small and the
angular
separations too close for easy detection. Here we propose to
discover
binaries in this observational gap through a Faint Guidance
Sensor
SNAP survey of relatively bright targets listed in the Galactic O
Star
Catalog. Our primary goal is to determine the binary frequency
among
those in the cluster/association, field, and runaway groups. The
results
will help us assess the role of binaries in massive star
formation
and in the processes that lead to the ejection of massive
stars
from their natal clusters. The program will also lead to the
identification
of new, close binaries that will be targets of long term
spectroscopic
and high angular resolution observations to determine
their
masses and distances. The results will also be important for the
interpretation
of the spectra of suspected and newly identified binary
and
multiple systems.
WFPC2
10915
ACS
Nearby Galaxy Survey
Existing
HST observations of nearby galaxies comprise a sparse and
highly
non-uniform archive, making comprehensive comparative studies
among
galaxies essentially impossible. We propose to secure HST's
lasting
impact on the study of nearby galaxies by undertaking a
systematic,
complete, and carefully crafted imaging survey of ALL
galaxies
in the Local Universe outside the Local Group. The resulting
images
will allow unprecedented measurements of: {1} the star formation
history
{SFH} of a >100 Mpc^3 volume of the Universe with a time
resolution
of Delta[log{t}]=0.25; {2} correlations between spatially
resolved
SFHs and environment; {3} the structure and properties of thick
disks
and stellar halos; and {4} the color distributions, sizes, and
specific
frequencies of globular and disk clusters as a function of
galaxy
mass and environment. To reach these goals, we will use a
combination
of wide-field tiling and pointed deep imaging to obtain
uniform
data on all 72 galaxies within a volume-limited sample extending
to
~3.5 Mpc, with an extension to the M81 group. For each galaxy, the
wide-field
imaging will cover out to ~1.5 times the optical radius and
will
reach photometric depths of at least 2 magnitudes below the tip of
the
red giant branch throughout the limits of the survey volume. One
additional
deep pointing per galaxy will reach SNR~10 for red clump
stars,
sufficient to recover the ancient SFH from the color-magnitude
diagram.
This proposal will produce photometric information for ~100
million
stars {comparable to the number in the SDSS survey} and uniform
multi-
color images of half a square degree of sky. The resulting
archive
will establish the fundamental optical database for nearby
galaxies,
in preparation for the shift of high- resolution imaging to
the
near-infrared.
WFPC2
11029
WFPC2
CYCLE 15 Intflat Linearity Check and Filter Rotation Anomaly
Monitor
Intflat
observations will be taken to provide a linearity check: the
linearity
test consists of a series of intflats in F555W, in each gain
and
each shutter. A combination of intflats, visflats, and earthflats
will
be used to check the repeatability of filter wheel motions.
{Intflat
sequences tied to decons, visits 1-18 in prop 10363, have been
moved
to the cycle 15 decon proposal xxxx for easier scheduling.} Note:
long-exposure
WFPC2 intflats must be scheduled during ACS anneals to
prevent
stray light from the WFPC2 lamps from contaminating long ACS
external
exposures.
WFPC2
11038
Narrow
Band and Ramp Filter Closeout
These
observations are to improve calibration of narrow band and ramp
filters.
We also test for changes in the filter properties during
WFPC2's
14 years on-board HST.
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 Monte Carlo
technique to
optimally
schedule our observations.
WFPC2
11201
Systemic
and Internal motions of the Magellanic Clouds: Third Epoch
Images
In
Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields in
the
Magellanic Clouds centered on background quasars. We used these data
to
determine the proper motions of the LMC and SMC to better than 5% and
15%
respectively. These are by far the best determinations of the proper
motions
of these two galaxies. The results have a number of unexpected
implications
for the Milky Way-LMC-SMC system. The implied
three-dimensional
velocities are larger than previously believed, and
are
not much less than the escape velocity in a standard 10^12 solar
mass
Milky Way dark halo. Orbit calculations suggest the Clouds may not
be
bound to the Milky Way or may just be on their first passage, both of
which
would be unexpected in view of traditional interpretations of the
Magellanic
Stream. Alternatively, the Milky Way dark halo may be a
factor
of two more massive than previously believed, which would be
surprising
in view of other observational constraints. Also, the
relative
velocity between the LMC and SMC is larger than expected,
leaving
open the possibility that the Clouds may not be bound to each
other.
To further verify and refine our results we now request an epoch
of
WFPC2/PC data for the fields centered on 40 quasars that have at
least
one epoch of ACS imaging. We request execution in snapshot mode,
as
in our previous programs, to ensure the most efficient use of HST
resources.
A third epoch of data of these fields will provide crucial
information
to verify that there are no residual systematic effects in
our
previous measurements. More importantly, it will increase the time
baseline
from 2 to 5 yrs and will increase the number of fields with at
least
two epochs of data. This will reduce our uncertainties
correspondingly,
so that we can better address whether the Clouds are
indeed
bound to each other and to the Milky Way. It will also allow us
to
constrain the internal motions of various populations within the
Clouds,
and will allow us to determine a distance to the LMC using
rotational
parallax.
WFPC2
11292
The
Ring Plane Crossings of Uranus in 2007
The
rings of Uranus turn edge-on to Earth in May and August 2007. In
between,
we will have a rare opportunity to see the unlit face of the
rings.
With the nine optically thick rings essentially invisible, we
will
observe features and phenomena that are normally lost in their
glare.
We will use this opportunity to search thoroughly for the
embedded
"shepherd" moons long believed to confine the edges of the
rings,
setting a mass limit roughly 10 times smaller than that of the
smallest
shepherd currently known, Cordelia. We will measure the
vertical
thicknesses of the rings and study the faint dust belts only
known
to exist from a single Voyager image. We will also study the
colors
of the newly-discovered faint, outer rings; recent evidence
suggests
that one ring is red and the other blue, implying that each
ring
is dominated by a different set of physical processes. We will
employ
near- edge-on photometry from 2006 and 2007 to derive the
particle
filling factor within the rings, to observe how ring epsilon
responds
to the "traffic jam" as particles pass through its narrowest
point,
and to test the latest models for preserving eccentricities and
apse
alignment within the rings. Moreover, this data set will allow us
to
continue monitoring the motions of the inner moons, which have been
found
to show possibly chaotic orbital variations; by nearly doubling
the
time span of the existing Hubble astrometry, the details of the
variations
will become much clearer.
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
09
09
FGS
REacq
05
05
OBAD
with Maneuver
28
28
SIGNIFICANT
EVENTS:
NICMOS
Recovery Flash Report:
NICMOS
recovery procedure was successfully completed at 246/15:03 UTC.
This
procedure enabled NICMOS Buffer Box 2 and transitioned NICMOS up to
Operate
mode and then back down to SAAOPER. The mode transition was
performed
in order to refresh the Buffer Box (BB) telemetry. The current
temperatures
for BB1, 2 and 3 are -1.94, -7.76 and -2.42 respectively.
NICMOS
is now configured to intercept science at the next available
opportunity.
The nominal plan is to intercept science at the beginning
of
next week's SMS (Day 253).