HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT #4902
PERIOD
COVERED: 5am August 4 - 5am August 5, 2009 (DOY 216/09:00z-217/09:00z)
OBSERVATIONS
SCHEDULED
ACS/WFC3
11586
Exceptional
Galactic Halo Globular Clusters and the Second Parameter
We
propose to obtain deep ACS-WFC images of six globular clusters (five
of
which have no previous HST photometry) that reside in the Galactic
halo,
where the second parameter effect is most pronounced. These
globular
clusters are among the least studied in the Galaxy and yet,
from
the perspective of the second parameter phenomenon, the most
intriguing.
With
the best available CMDs only reaching the vicinity of the main
sequence
turn off at present, the unique sensitivity and resolution of
ACS-WFC
will yield ages of unprecedented precision for these clusters.
These
data will provide us with new insight into the stellar populations
present
in the outer Galactic halo and the nature of the second
parameter.
The second parameter plays a critical role in our
understanding
of the formation and evolution of the Galaxy and the
proposed
observations will shed new light on this problem and these
exceptional
clusters.
ACS/WFC3
11882
CCD
Hot Pixel Annealing
All
the data for this program is acquired using internal targets (lamps)
only,
so all of the exposures should be taken during Earth occultation
time
(but not during SAA passages). This program emulates the ACS
pre-flight
ground calibration and post launch SMOV testing (program
8948),
so that results from each epoch can be directly compared.
Extended
Pixel Edge Response (EPER) and First Pixel Response (FPR) data
will
be obtained over a range of signal levels for the Wide Field
Channel
(WFC). The High Resolution Channel (HRC) visits have been
removed
since it could not be repaired during SM4.
COS
11474
COS
NUV Internal/External Wavelength Scales
Observe
external radial velocity standard targets (preferably, though
not
required, in CVZ) in TIME-TAG (FLASH=YES) mode with as many grating
and
central wavelength combinations as feasible. The purpose is to
obtain
zero-point offsets for the wavelength scale (internal wavecal
lamp
scale to external standard wavelength scale) for all central
wavelengths.
Following this determination, adjustments of the nominal
science
target spectral range for each grating and central wavelength
combination
will be made via SMS patchable constant for nominal OSM2
positions
corresponding to each central wavelength. Subsequent to this
modification
of the wavelength scale (and its verification in COS 15 -
program
11475), NUV science-related operations and wavelength-scale
dependent
EROs can commence.
COS
11475
COS
Internal NUV Wavelength Verification
This
program will be executed after the uplink of the OSM2 position
updates
derived from the determination of the wavelength-scale zero
points
and desired spectral ranges for each grating in activity COS14
(program
11474 - COS NUV Internal/External Wavelength Scales). This
program
will verify that the operational spectral ranges for each
grating,
central wavelength, and FP-POS are those desired. Subsequent to
a
successful verification, COS NUV ERO observations and NUV science can
be
enabled. An internal wavelength calibration spectrum using the
default
PtNe lamp (lamp 1) with each NUV grating at each central
wavelength
setting and each FP-POS position will be obtained for the
verification.
Additional exposures and waits between certain exposures
will
be required to avoid - and to evaluate - mechanism drifts.
FGS
11704
The
Ages of Globular Clusters and the Population II Distance Scale
Globular
clusters are the oldest objects in the universe whose age can
be
accurately determined. The dominant error in globular cluster age
determinations
is the uncertain Population II distance scale. We propose
to
use FGS 1r to obtain parallaxes with an accuracy of 0.2
milliarcsecond
for 9 main sequence stars with [Fe/H] < -1.5. This will
determine
the absolute magnitude of these stars with accuracies of 0.04
to
0.06mag. This data will be used to determine the distance to 24
metal-poor
globular clusters using main sequence fitting. These
distances
(with errors of 0.05 mag) will be used to determine the ages
of
globular clusters using the luminosity of the subgiant branch as an
age
indicator. This will yield absolute ages with an accuracy 5%, about
a
factor of two improvement over current estimates. Coupled with
existing
parallaxes for more metal-rich stars, we will be able to
accurately
determine the age for globular clusters over a wide range of
metallicities
in order to study the early formation history of the Milky
Way
and provide an independent estimate of the age of the universe.
The
Hipparcos database contains only 1 star with [Fe/H] < -1.4 and an
absolute
magnitude error less than 0.18 mag which is suitable for use in
main
sequence fitting. Previous attempts at main sequence fitting to
metal-poor
globular clusters have had to rely on theoretical
calibrations
of the color of the main sequence. Our HST parallax program
will
remove this source of possible systematic error and yield distances
to
metal- poor globular clusters which are significantly more accurate
than
possible with the current parallax data. The HST parallax data will
have
errors which are 10 times smaller than the current parallax data.
Using
the HST parallaxes, we will obtain main sequence fitting distances
to
11 globular clusters which contain over 500 RR Lyrae stars. This will
allow
us to calibrate the absolute magnitude of RR Lyrae stars, a
commonly
used Population II distance indicator.
STIS/CCD
11844
CCD
Dark Monitor Part 1
Monitor
the darks for the STIS CCD.
STIS/CCD
11846
CCD
Bias Monitor-Part 1
Monitor
the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1,
and
1x1 at gain = 4, to build up high-S/N superbiases and track the
evolution
of hot columns.
STIS23
11393
STIS-23
FUV MAMA Image Quality
This
proposal will measure the FUV spectroscopic PSF along the length of
a
long slit. It will do this by observing a point source with the 52X0.1
aperture
and the G140L grating, using a seven-point centered
perpendicular-to-slit
LINE pattern with 0.1 arcsec spacing to measure
centering
of the target. This seven-point pattern will be done at three
different
positions along the length of the aperture, including both the
repeller
offset aperture position (three arcseconds below repeller wire)
and
the D1 position, which is located at a position of low FUV dark
current
2 arcseconds from the bottom edge. A third position along the
aperture
is 6.0" above the repeller offset position is included. A
single
exposure at nominal position will also be taken through the
photometric
52X2 aperture to provide a reference for estimating the
small
slit throughput. Sufficient targets will be provided to allow this
test
to be executed at any time during the BEA period..
WFC3
11426
UVIS
SMOV Contamination Monitor
The
UV throughput of WFC3 during SMOV is monitored via weekly standard
star
observations in a subset of key filters (as many as will fit into a
single
orbit but to include at a minimum F218W, F225W, F275W, and
F606W).
The data will provide a measure of throughput levels as a
function
of time and wavelength, allowing for detection of the presence
of
possible contaminants. In addition, a small set of internal exposures
are
included with the externals, to provide verification of detector
stability.
This
proposal corresponds to Activity WFC3-13.
WFC3
11446
WFC3
UVIS Dark Current, Readnoise, and CTE
This
proposal obtains full-frame, four-amp readout bias and dark frames
at
regularly- spaced intervals throughout SMOV in order to assess and
monitor
dark current, bad (warm, hot, dead) pixels, and readnoise. In
addition,
a set of internals using the WFC3 calsystem are taken to
provide
a baseline CTE measurement. WFC3-33
WFC3
11447
WFC3
IR Dark Current, Readnoise, and Background
This
proposal obtains full-frame, four-amp readout images.
Un-illuminated
internals are taken at regularly spaced intervals
throughout
SMOV in order to assess and monitor readnoise and dark
current
(of both light-sensitive pixels and reference pixels), and bad
(warm,
hot, dead, variable) pixels. In addition, externals aimed at
fields
with sparse stellar density are taken to measure diffuse
background
light.
This
program corresponds to WFC3-34.
WFC3
11552
Characterization
of the WFC3 IR Grisms
Image
displacement, spectral trace and dispersion, and throughput of the
IR
G102 and G141 grisms will be verified. The HST flux standard GD 153
will
be observed in a 5-point pattern in the IR field of view, which
will
provide image displacement, spectral trace, and throughput
measurements
as a function of location within the FOV. Similarly, the
planetary
nebula PN HB12 will be observed in a 9-point pattern in the IR
field
of view, which will provide dispersion measurements as a function
of
FOV position.
WFC3
11808
WFC3
UVIS Bowtie Monitor
The
UVIS detector was observed during ground testing to occasionally
exhibit
flat field and dark variations with a bowtie pattern. These
variations
are most significant as ~1% flat field (gain) variations
across
the field of view. It is believed that this represents a state or
condition
into which the detector can transition for reasons and under
circumstances
which are not currently understood. It is also very
unlikely
that most science observations will determine the state (bowtie
or
no-bowtie) of the detector. Ground test data indicates that this
state
is long lived (many hours to ~one day). Hysteresis or memory of
past
light exposure is also associated with this state.
Recent
evidence suggests that exposing the detector to ~200k to 500k
electrons
may quench this state. This proposal obtains an internal flat
field
sequence of three exposures: one at 10x full well with two at 0.5x
full
well immediately before and after. Each exposure is 3x3 binned to
reduce
the data volume required.
These
visits should be scheduled 2x per day until further direction is
provided.
WFC3/UVI/IR
11570
Narrowing
in on the Hubble Constant and Dark Energy
A
measurement of the Hubble constant to a precision of a few percent
would
be a powerful aid to the investigation of the nature of dark
energy
and a potent "end-to-end" test of the present cosmological model.
In
Cycle 15 we constructed a new, streamlined distance ladder utilizing
high-quality
type Ia supernova data and observations of Cepheids with
HST
in the near-IR to minimize the dominant sources of systematic
uncertainty
in past measurements of the Hubble constant and reduce its
total
uncertainty to a little under 5%. Here we propose to exploit this
new
route to reduce the remaining uncertainty by more than 30%,
translating
into an equal reduction in the uncertainty of the equation
of
state of dark energy. We propose three sets of observations to reach
this
goal: a mosaic of NGC 4258 with WFC3 in F160W to triple its sample
of
long period Cepheids, WFC3/F160W observations of the 6 ideal SN Ia
hosts
to triple their samples of Cepheids, and observations of NGC 5584
the
host of a new SN Ia, SN 2007af, to discover and measure its Cepheids
and
begin expanding the small set of SN Ia luminosity calibrations.
These
observations would provide the bulk of a coordinated program aimed
at
making the measurement of the Hubble constant one of the leading
constraints
on dark energy.
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
11964
- GSAcq(2,1,1) scheduled at 216/14:17:09 and at 216/15:52:33 resulted
in fine lock backup (1,0,1) using FGS-1 due to scan step limit
exceeded
on FGS-2.
Observations possibly affected: ACS 21 thru 30 Proposal ID# 11586
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSAcq
9
9
FGS
REAcq
7
7
OBAD
with Maneuver
8
8
SIGNIFICANT
EVENTS: (None)