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 # 4418
PERIOD COVERED: UT August 2, 2007 (DOY 214)
OBSERVATIONS SCHEDULED
NIC1/NIC2/NIC3 8794
NICMOS Post-SAA calibration - CR Persistence Part 5
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.
NIC2 10854
Coronagraphic Imaging of Bright New Spitzer Debris Disks
II.
Fifteen percent of bright main sequence stars possess
dusty
circumstellar debris disks revealed by far-infrared
photometry. These
disks are signposts of planetary systems: collisions among
larger,
unseen parent bodies maintain the observed dust population
against
losses to radiation pressure and P-R drag. Images of
debris disks at
optical, infrared, and millimeter wavelengths have shown
central holes,
rings, radial gaps, warps, and azimuthal asymmetries which
indicate the
presence of planetary mass perturbers. Such images provide
unique
insights into the structure and dynamics of exoplanetary
systems.
Relatively few debris disks have been spatially resolved.
Only thirteen
have ever been resolved at any wavelength, and at
wavelengths < 10
microns {where subarcsec resolution is available}, only
ten. Imaging of
many other debris disk targets has been attempted with
various HST
cameras/coronagraphs and adaptive optics, but without
success. The key
property which renders a debris disk observable in
scattered light is
its dust optical depth. The ten disks imaged so far all
have a dust
excess luminosity >~ 0.01% that of the central star; no
disks with
smaller optical depths have been detected. Most main
sequence stars
known to meet this requirement have already been observed,
so future
progress in debris disk imaging depends on discovering
additional stars
with large infrared excess. The Spitzer Space Telescope
offers the best
opportunity in 20 years to identify new examples of high
optical depth
debris disk systems. We propose to complete ACS
coronagraphic imaging
followup of bright, new debris disks discovered during the
first two
years of the Spitzer mission, by observing three
additional targets in
Cycle 15. Our goal is to obtain the first resolved images
of these disks
at ~3 AU resolution, define the disk sizes and
orientations,and uncover
disk substructures indicative of planetary perturbations.
The results
will open wider a window into the structure of planetary
systems.
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 11084
Probing the Least Luminous Galaxies in the Local Universe
We propose to obtain deep color-magnitude data of eight new
Local Group
galaxies which we recently discovered: Andromeda XI,
Andromeda XII, and
Andromeda XIII {satellites of M31}; Canes Venatici I,
Canes Venatici II,
Hercules, and Leo IV {satellites of the Milky Way}; and
Leo T, a new
"free-floating" Local Group dwarf spheroidal
with evidence for recent
star formation and associated H I gas. These represent the
least
luminous galaxies known at *any* redshift, and are the
only accessible
laboratories for studying this extreme regime of galaxy
formation. With
deep WFPC-2 F606W and F814W pointings at their centers, we
will
determine whether these objects contain single or multiple
age stellar
populations, as well as whether these objects display a
range of
metallicities.
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/NIC3 11188
First Resolved Imaging of Escaping Lyman Continuum
The emission from star-forming galaxies appears to be
responsible for
reionization of the universe at z>6. However, the
models that attempt to
describe the detailed impact of high- redshift galaxies on
the
surrounding inter-galactic medium {IGM} are strongly
dependent upon
several uncertain parameters. Perhaps the most uncertain
is the fraction
of HI-ionizing photons produced by young stars which
escape into the
IGM. Most attempts to measure this "escape
fraction" {f_esc} have
produced null results. Recently, a small subset of z~3
Lyman Break
Galaxies {LBGs} has been found exhibiting large escape
fractions. It
remains unclear however, what differentiates them from
other LBGs.
Several models attempt to explain how such a large
fraction of ionizing
continuum can escape through the HI and dust in the ISM
{eg. "chimneys"
created by SNe winds, globular cluster formation, etc.},
each producing
unique signatures which can be observed with resolved
imaging of the
escaping Lyman continuum. We propose a deep, high
resolution WFPC2 image
of the ionizing continuum {F336W} and the rest-frame 1500
Angstrom
continuum {F606W} of five of the six known LBGs with large
escape
fractions. These LBGs all fit within a single WFPC2
pointing, yielding
high observing efficiency. Additionally, they all have
z~3.1 or higher,
the optimal redshift range for probing the Lyman Continuum
region with
available WFPC2 filters. These factors make our proposed
sample
especially suitable for follow- up. With these data we
will discern the
mechanisms responsible for producing large escape
fractions, and
therefore gain insight into the process of reionization.
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
07
07
FGS
REacq 06
06
OBAD with Maneuver
26
26
SIGNIFICANT EVENTS: (None)