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Daily Report #5089



 
 
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Old May 5th 10, 02:46 PM posted to sci.astro.hubble
Cooper, Joe
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Default Daily Report #5089


HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5089

PERIOD COVERED: 5am May 4 - 5am May 5, 2010 (DOY 124/09:00z-125/09:00z)

OBSERVATIONS SCHEDULED

ACS/WFC 11995
CCD Daily Monitor (Part 2)

This program comprises basic tests for measuring the read noise and
dark current of the ACS WFC and for tracking the growth of hot pixels.
The recorded frames are used to create bias and dark reference images
for science data reduction and calibration. This program will be
executed four days per week (Mon, Wed, Fri, Sun) for the duration of
Cycle 17. To facilitate scheduling, this program is split into three
proposals. This proposal covers 320 orbits (20 weeks) from 1 February
2010 to 20 June 2010.


ACS/WFC/WFC3/UVI 11636
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 that escape
into the IGM. Most attempts to measure this "escape fraction" 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. To date, there are only six
LBGs with individual detections of escaping Lyman continuum at any
redshift. We propose a single deep, high resolution WFC3/UVIS image of
the ionizing continuum (F336W) and the rest-frame UV/optical
(F606W/F814W/F160W) of five of these six LBGs with large escape
fractions. These LBGs have a high surface density and large escape
fractions, and lie at the optimal redshift for Lyman continuum imaging
with UVIS filters, making our 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.

ACS/WFC/WFC3/UVI 1739
Multiple Stellar Generations in the Unique Globular Clusters NGC 6388
and NGC 6441

Over the last few years HST observations have resulted in one of the
most exciting and unexpected developments in stellar population
studies: the discovery of multiple generations of stars in several
globular clusters. The finding of multiple main sequences in the
massive clusters NGC 2808 and Omega Centauri, and multiple subgiant
branches in NGC 1851, M54, and NGC 6388 has challenged the long-held
paradigm that globular clusters are simple stellar populations. Even
more surprising, given the spectroscopic and photometric constraints,
the only viable explanation for the main sequence splitting appears to
be Helium enrichment, up to an astonishingly high Y=0.4. The
conditions under which certain globulars experience the formation of
multiple stellar generations remain mysterious, and even more so the
helium-enrichment phenomenon. Such an enrichment has important
implications for chemical-enrichment, star-formation, and
stellar-evolution scenarios, in star clusters and likely elsewhere. To
properly constrain the multiple main sequence phenomenon, it is
important to determine its extent among GCs: is it limited to Omega
Cen and NGC2808, or is it more common? We propose deep WFC3 optical/IR
imaging of NGC 6388 and 6441, the two globular clusters that are most
likely to host multiple, helium-enriched populations. Our simulations
of WFC3 performance suggest that we will be able to detect even the
main sequence splittings caused by small He differences (Delta Y
0.03).

ACS/WFC/WFC3/UVI 12020
The Deepest Stellar X-ray/optical Census of the Bulge

We have obtained the deepest optical dataset ever taken or planned
towards the bulge, allowing bulge/disk decomposition down to F606W=23
and variability monitoring over seven days, diagnostics not available
for any bulge field observed by Chandra. We propose ACIS-I imaging to
identify X-ray point sources in this field. This will directly trace a
number of fundamental yet poorly-constrained parameters of the inner
Milky Way, for example the spin-down timescale of stars along the disk
and bulge; the formation history of the bulge and, for the first time,
direct constraints on the gravitational potential of the inner milky
way through AGN-enabled absolute proper motions. Our proposed survey
will be an essential calibrator for other X-ray/optical surveys of the
bulge both past and planned.

COS/FUV/COS/NUV 11645
HST COS Observations of the Atmosphere and Airglow/Aurora of Enceladus

Recent observations from several instruments on the Cassini spacecraft
have revealed plumes of dust and water from the southern polar region,
and clearly shown that Enceladus contributes large amounts of plasma
to Saturn?s magnetosphere. This implies a global thin atmosphere
containing water and likely other species, and a local region with
orders of magnitude higher density near the plumes. While water and
dust have been identified from the plumes, the presence of many other
species in the atmosphere is possible and not yet ruled out. The
identification of all significant species in the atmosphere of
Enceladus is of key importance to speculation about the source of the
water plumes, and the implications for any form of life at or below
the surface. In addition, modeling suggests that Enceladus? mass
loading region may be comparable in extent to Io?s, and interacts
strongly with Saturn?s corotating magnetic field and plasma. We have
recently concluded a search for an auroral footprint of Enceladus in
HST images, which set a low upper limit implying that the
magnetospheric interaction is concentrated near Enceladus, rather than
being communicated along field lines to Saturn?s ionosphere. The next
step will be to observe the interaction at the satellite, and to learn
whatever we can about the physics of the release of the atmospheric
gas. We propose here an exploratory set of spectral observations with
HST COS to measure the solar reflection spectrum over a broad range of
UV wavelengths for atmospheric absorption signatures. This will at the
same time measure the emission spectrum of the atmosphere from both
the leading and trailing hemispheres ? Enceladus orbit apart, as was
done in HST STIS observations of Io to study its interaction at
Jupiter. The higher sensitivity of COS will be needed to study the
much smaller and relatively weakly-interacting Enceladus, and the
outcome of these observations will determine the nature of future
studies of the atmosphere of Enceladus and its plasma interaction with
the Saturnian magnetosphere.

COS/NUV/S/C 11891
NUV MAMA Fold Distribution

The performance of MAMA microchannel plate can be monitored using a
MAMA fold analysis procedure. The fold analysis provides a measurement
of the distribution of charge cloud sizes incident upon the anode
giving some measure of changes in the pulse-height distribution of the
MCP and, therefore, MCP gain. This proposal executes the same steps as
the COS SMOV as proposal 13555 (visit 5).

STIS/CCD 11845
CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CCD 11847
CCD Bias Monitor-Part 2

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.

STIS/CCD/STIS/MA2 11568
A SNAPSHOT Survey of the Local Interstellar Medium: New NUV
Observations of Stars with Archived FUV Observations

We propose to obtain high-resolution STIS E230H SNAP observations of
MgII and FeII interstellar absorption lines toward stars within 100
parsecs that already have moderate or high-resolution far-UV (FUV),
900-1700 A, observations available in the MAST Archive. Fundamental
properties, such as temperature, turbulence, ionization, abundances,
and depletions of gas in the local interstellar medium (LISM) can be
measured by coupling such observations. Due to the wide spectral range
of STIS, observations to study nearby stars also contain important
data about the LISM embedded within their spectra. However, unlocking
this information from the intrinsically broad and often saturated FUV
absorption lines of low-mass ions, (DI, CII, NI, OI), requires first
understanding the kinematic structure of the gas along the line of
sight. This can be achieved with high resolution spectra of high-mass
ions, (FeII, MgII), which have narrow absorption lines, and can
resolve each individual velocity component (interstellar cloud). By
obtaining short (~10 minute) E230H observations of FeII and MgII, for
stars that already have moderate or high-resolution FUV spectra, we
can increase the sample of LISM measurements, and thereby expand our
knowledge of the physical properties of the gas in our galactic
neighborhood. STIS is the only instrument capable of obtaining the
required high resolution data now or in the foreseeable future.

STIS/MA1 11861
MAMA FUV Flats

This program will obtain FUV-MAMA observations of the STIS internal
Krypton lamp to construct an FUV flat applicable to all FUV modes.

STIS/MA2 11857
STIS Cycle 17 MAMA Dark Monitor

This proposal monitors the behavior of the dark current in each of the
MAMA detectors. The basic monitor takes two 1380s ACCUM darks each
week with each detector. However, starting Oct 5, pairs are only
included for weeks that the LRP has external MAMA observations
planned. The weekly pairs of exposures for each detector are linked so
that they are taken at opposite ends of the same SAA free interval.
This pairing of exposures will make it easier to separate long and
short term temporal variability from temperature dependent changes.
For both detectors, additional blocks of exposures are taken once
every six months. These are groups of five 1314 s FUV-MAMA TIME-TAG
darks or five 3x315 s NUV ACCUM darks distributed over a single SAA
free interval. This will give more information on the brightness of
the FUV MAMA dark current as a function of the amount of time that the
HV has been on, and for the NUV MAMA will give a better measure of the
short term temperature dependence.

WFC3/IR/WFC3/UVI 11644
A dynamical-compositional survey of the Kuiper belt:
a new window into the formation of the outer solar system

The eight planets overwhelmingly dominate the solar system by mass,
but their small numbers, coupled with their stochastic pasts, make it
impossible to construct a unique formation history from the dynamical
or compositional characteristics of them alone. In contrast, the huge
numbers of small bodies scattered throughout and even beyond the
planets, while insignificant by mass, provide an almost unlimited
number of probes of the statistical conditions, history, and
interactions in the solar system. To date, attempts to understand the
formation and evolution of the Kuiper belt have largely been dynamical
simulations where a hypothesized starting condition is evolved under
the gravitational influence of the early giant planets and an attempt
is made to reproduce the current observed populations. With little
compositional information known for the real Kuiper belt, the test
particles in the simulation are free to have any formation location
and history as long as they end at the correct point. Allowing
compositional information to guide and constrain the formation,
thermal, and collisional histories of these objects would add an
entire new dimension to our understanding of the evolution of the
outer solar system. While ground based compositional studies have hit
their flux limits already with only a few objects sampled, we propose
to exploit the new capabilities of WFC3 to perform the first ever
large-scale dynamical-compositional study of Kuiper belt objects
(KBOs) and their progeny to study the the chemical, dynamical, and
collisional history of the region of the giant planets. The
sensitivity of the WFC3 observations will allow us to go up to two
magnitudes deeper than our ground based studies, allowing us the
capability of optimally selecting a target list for a large survey
rather than simply taking the few objects that can be measured, as we
have had to do to date. We have carefully constructed a sample of 120
objects which provides both overall breadth, for a general
understanding of these objects, plus a large enough number of objects
in the individual dynamical subclass to allow detailed comparison
between and within these groups. These objects will likely define the
core Kuiper belt compositional sample for years to come. While we have
many specific results anticipated to come from this survey, as with
any project where the field is rich, our current knowledge level is
low, and a new instrument suddenly appears which can exploit vastly
larger segments of the population, the potential for discovery -- both
anticipated and not -- is extraordinary.

WFC3/UVI 11628
Globular Cluster Candidates for Hosting a Central Black Hole

We are continuing our study of the dynamical properties of globular
clusters and we propose to obtain surface brightness profiles for high
concentration clusters. Our results to date show that the distribution
of central surface brightness slopes do not conform to standard
models. This has important implications for how they form and evolve,
and suggest the possible presence of central intermediate-mass black
holes. From our previous archival proposals (AR-9542 and AR-10315), we
find that many high concentration globular clusters do not have flat
cores or steep central cusps, instead they show weak cusps. Numerical
simulations suggest that clusters with weak cusps may harbor
intermediate-mass black holes and we have one confirmation of this
connection with omega Centauri. This cluster shows a shallow cusp in
its surface brightness profile, while kinematical measurements suggest
the presence of a black hole in its center. Our goal is to extend
these studies to a sample containing 85% of the Galactic globular
clusters with concentrations higher than 1.7 and look for objects
departing from isothermal behavior. The ACS globular cluster survey
(GO-10775) provides enough objects to have an excellent coverage of a
wide range of galactic clusters, but it contains only a couple of the
ones with high concentration. The proposed sample consists of clusters
whose light profile can only be adequately measured from space-based
imaging. This would take us close to completeness for the high
concentration cases and therefore provide a more complete list of
candidates for containing a central black hole. The dataset will also
be combined with our existing kinematic measurements and enhanced with
future kinematic studies to perform detailed dynamical modeling.

WFC3/UVI 11630
Monitoring Active Atmospheres on Uranus and Neptune

We propose Snapshot observations of Uranus and Neptune to monitor
changes in their atmospheres on time scales of weeks and months, as we
have been doing for the past seven years. Previous Hubble Space
Telescope observations (including previous Snapshot programs 8634,
10170, 10534, and 11156), together with near-IR images obtained using
adaptive optics on the Keck Telescope, reveal both planets to be
dynamic worlds which change on time scales ranging from hours to
(terrestrial) years. Uranus equinox occurred in December 2007, and the
northern hemisphere is becoming fully visible for the first time since
the early 1960s. HST observations during the past several years
(Hammel et al. 2005, Icarus 175, 284 and references therein) have
revealed strongly wavelength-dependent latitudinal structure, the
presence of numerous visible-wavelength cloud features in the northern
hemisphere, at least one very long-lived discrete cloud in the
southern hemisphere, and in 2006 the first clearly defined dark spot
seen on Uranus. Long-term ground-based observations (Lockwood and
Jerzekiewicz, 2006, Icarus 180, 442; Hammel and Lockwood 2007, Icarus
186, 291) reveal seasonal brightness changes that seem to demand the
appearance of a bright northern polar cap within the next few years.
Recent HST and Keck observations of Neptune (Sromovsky et al. 2003,
Icarus 163, 256 and references therein) show a general increase in
activity at south temperate latitudes until 2004, when Neptune
returned to a rather Voyager-like appearance with discrete bright
spots rather than active latitude bands. Further Snapshot observations
of these two dynamic planets will elucidate the nature of long-term
changes in their zonal atmospheric bands and clarify the processes of
formation, evolution, and dissipation of discrete albedo features.

WFC3/UVI 11905
WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set
of full-frame, four-amp biasBRand dark frames. A smaller set of
2Kx4K subarray biases are acquired at less frequent
intervalsBRthroughout the cycle to support subarray science
observations. The internals from this proposal,BRalong with those
from the anneal procedure (11909), will be used to generate the
necessary superbiasBRand superdark reference files for the
calibration pipeline (CDBS).

WFC3/UVI 11908
Cycle 17: UVIS Bowtie Monitor

Ground testing revealed an intermittent hysteresis type effect in the
UVIS detector (both CCDs) at the level of ~1%, lasting hours to days.
Initially found via an unexpected bowtie-shaped feature in flatfield
ratios, subsequent lab tests on similar e2v devices have since shown
that it is also present as simply an overall offset across the entire
CCD, i.e., a QE offset without any discernable pattern. These lab
tests have further revealed that overexposing the detector to count
levels several times full well fills the traps and effectively
neutralizes the bowtie. Each visit in this proposal acquires a set of
three 3x3 binned internal flatfields: the first unsaturated image will
be used to detect any bowtie, the second, highly-exposed image will
neutralize the bowtie if it is present, and the final image will allow
for verification that the bowtie is gone.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)

HSTARS:

12269 - STIS Status Buffer Messages #645, #646 and #556 received
124/22:54:24z-124/22:55:29z

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSAcq 10 10
FGS REAcq 6 6
OBAD with Maneuver 7 7

SIGNIFICANT EVENTS:

Flash Report

At 124/22:54z, during a STIS MAMA1 monitor HV ramp, two consecutive
event yellow limits were exceeded. After the second consecutive out of
limit, the HV was turned off and event flag 2 was set.

 




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