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Daily Report #4330



 
 
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Old March 30th 07, 04:36 PM posted to sci.astro.hubble
Bassford, Lynn
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Posts: 44
Default Daily Report #4330

Notice: For the foreseeable future, the daily reports may contain apparent
discrepancies between some proposal descriptions and the listed instrument
usage. This is due to the conversion of previously approved ACS WFC or HRC
observations into WFPC2, or NICMOS observations subsequent to the loss of
ACS CCD science capability in late January.

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4330

PERIOD COVERED: UT March 29, 2007 (DOY 088)

OBSERVATIONS SCHEDULED

ACS/SBC 10810

The Gas Dissipation Timescale: Constraining Models of Planet Formation

We propose to constrain planet-formation models by searching for molecular
hydrogen emission around young {10-50 Myr} solar-type stars that have
evidence for evolved dust disks. Planet formation models show that the
presence of gas in disks is crucial to the formation of BOTH giant and
terrestrial planets, influences dust dynamics, and through tidal
interactions with giant planets leads to orbital migration. However, there
is a lack of systematic information on the presence and lifetime of gas
residing at planet-forming radii. We will use a newly identified broad
continuum emission feature of molecular hydrogen at 1600 Angstrom to search
for residual gas within an orbital radius of 5-10 AU around young stars that
have evolved beyond the optically thick T Tauri phase. These observations
will enable the most sensitive probe to date of remant gas in circumstellar
disks, detecting surfaces densites of ~0.0001 g/cm^2, or less than 10^-5 of
the theoretical "mininum mass" solar nebula from which our solar system is
thought to have formed. Our observations are designed to be synergistic with
ongoing searches for gas emission that is being performed using the Spitzer
Space Telescope in that the proposed HST observations are ~100 times more
sensitive and will have 50 times higher angular resolution. These combined
studies will provide the most comprehensive view of residual gas in
proto-planetary disks and can set important constraints on models of planet
formation.

NIC2 10858

NICMOS Imaging of the z ~ 2 Spitzer Spectroscopic Sample of
Ultraluminous Infrared Galaxies

We propose to obtain NICMOS images of the first large sample of high-z
ultra-luminous infrared galaxies {ULIRGs} whose redshifts and physical
states have been determined with Spitzer mid-IR spectra. The detection of
strong silicate absorption and/or PAH emission lines suggest that the these
sources are a mixture of highly obscured starbursts, AGNs and composite
systems at z=2. Although some of the spectra show PAH emission similar to
local starburst ULIRGs, their bolometric luminosities are roughly an order
of magnitude higher. One important question is if major mergers, which are
the trigger for 95% of local ULIRGs, also drive this enormous energy output
observed in our z=2 sample. The NICMOS images will allow us to {1} measure
surface brightness profiles of z~2 ULIRGs and establish if major mergers
could be common among our luminous sources at these early epochs, {2}
determine if starbursts and AGNs classified based on their mid-IR spetra
would have different morphological signatures, thus different dynamic state;
{3} make comparisons with the similar studies of ULIRGs at z ~ 0 - 1, thus
infer any evolutionary connections between high-z ULIRGs and the formation
of normal, massive galaxies and quasars observed today.

WFPC2 10886

The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

As a continuation of the highly successful Sloan Lens ACS {SLACS} Survey for
new strong gravitational lenses, we propose one orbit of ACS-WFC F814W
imaging for each of 50 high-probability strong galaxy-galaxy lens
candidates. These observations will confirm new lens systems and permit
immediate and accurate photometry, shape measurement, and mass modeling of
the lens galaxies. The lenses delivered by the SLACS Survey all show
extended source structure, furnishing more constraints on the projected lens
potential than lensed-quasar image positions. In addition, SLACS lenses have
lens galaxies that are much brighter than their lensed sources, facilitating
detailed photometric and dynamical observation of the former. When confirmed
lenses from this proposal are combined with lenses discovered by SLACS in
Cycles 13 and 14, we expect the final SLACS lens sample to number 80--100:
an approximate doubling of the number of known galaxy-scale strong
gravitational lenses and an order-of-magnitude increase in the number of
optical Einstein rings. By virtue of its homogeneous selection and sheer
size, the SLACS sample will allow an unprecedented exploration of the mass
structure of the early-type galaxy population as a function of all other
observable quantities. This new sample will be a valuable resource to the
astronomical community by enabling qualitatively new strong lensing science,
and as such we will waive all but a short {3-month} proprietary period on
the observations.

FGS 10612

Binary Stars in Cyg OB2: Relics of Massive Star Formation in a
Super-Star Cluster

We propose to make a high angular resolution SNAP survey of the massive
stars in the nearby, super-star cluster Cyg OB2. We will use FGS1r TRANS
mode observations to search for astrometric companions in the separation
range of 0.01 to 1.00 arcsec and in the magnitude difference range smaller
than 4 magnitudes. The observations will test the idea that the formation of
very massive stars involves mergers and the presence of nearby companions.
Discovery of companions to massive stars in this relatively nearby complex
will provide guidance in the interpretation of apparently supermassive stars
in distant locations. The search for companions will also be important for
verification of fundamental parameters derived from spectroscopy,
adjustments to main sequence fitting and distance estimations, determining
third light contributions of eclipsing binaries, identifying wide colliding
wind binaries, studying the relationship between orbital and spin angular
momentum, and discovering binaries amenable to future mass determinations.
The massive star environment in Cyg OB2 may be similar to the kinds found in
the earliest epoch of star formation, so that a study of the role of
binaries in Cyg OB2 will help us understand the formation processes of the
first stars in the Universe.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration - CR Persistence Part 6

A new proceedure proposed to alleviate the CR-persistence problem of NICMOS.
Dark frames will be obtained immediately upon exiting the SAA contour 23,
and everytime 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 i mages. Each observation will need its own CRMAP, as
different SAA passages leave different imprints on the NICMOS detectors.

WFPC2 10869

The upper atmosphere and the escape state of the transiting
very-hot-Jupiter HD189733b

The observation of the HD209458b transits in Lyman-alpha revealed that the
atmosphere of this planet is escaping. These observations raised the
question of the evaporation state of hot-Jupiters. Is the evaporation
specific to HD209458b or general to hot-Jupiters? What is the evaporation
mechanism, and how does the escape rate depend on the planetary system
characteristics? The recent discovery of HD189733b, a planet transiting a
bright and nearby K0 star {V=7.7}, offers the unprecedented opportunity to
answer these questions. Indeed, among the stars harboring transiting
planets, HD189733 presents the largest apparent brightness in Lyman-alpha,
providing capabilities to constrain the escape rate to high accuracy. With
ACS/PR110L we will observe stellar emission lines to search for atmospheric
absorptions during the transits. HD189733b being a very short period planet
orbiting a nearby late type star with bright chromospheric emission lines,
it is by far the best target to make significant progress in that field.

WFPC2 11030

WFPC2 WF4 Temperature Reduction #3

In the fall of 2005, a serious anomaly was found in images from the WF4 CCD
in WFPC2. The WF4 CCD bias level appeared to have become unstable, resulting
in sporadic images with either low or zero bias level. The severity and
frequency of the problem was rapidly increasing, making it possible that WF4
would soon become unusable if no work-around were found. Examination of bias
levels during periods with frequent WFPC2 images showed low and zero bias
episodes every 4 to 6 hours. This periodicity is driven by cycling of the
WFPC2 Replacement Heater, with the bias anomalies occurring at the
temperature peaks. The other three CCDs {PC1, WF2, and WF3} appear to be
unaffected and continue to operate properly. Lowering the Replacement Heater
temperature set points by a few degrees C effectively eliminates the WF4
anomaly. On 9 January 2006, the upper set point of the WFPC2 Replacement
Heater was reduced from 14.9C to 12.2C. On 20 February 2006, the upper set
point was reduced from 12.2C to 11.3C, and the lower set point was reduced
from 10.9C to 10.0C. These changes restored the WF4 CCD bias level; however,
the bias level has begun to trend downwards again, mimicking its behavior in
late 2004 and early 2005. A third temperature reduction is planned for March
2007. We will reduce the upper set point of the heater from 11.3C to 10.4C
and the lower set point from 10.0C to 9.1C. The observations described in
this proposal will test the performance of WFPC2 before and after this
temperature reduction. Additional temperature reductions may be needed in
the future, depending on the performance of WF4. Orbits: internal 26,
external 1

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10760 - GSAcq(1,2,2) failed to RGA Hold (Gyro Control

Upon acquisition of signal at 088/09:59:55, the GSAcq(1,2,2) scheduled at
088/09:39:54 - 09:47:59 had failed to RGA Hold due to (QF1STOPF) stop flag
indication on FGS1. Pre-acquisition OBADs (RSS) attitude correction values
not available due to LOS. Post-acq OBAD/MAP had (RSS) of 7.58 arcseconds.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 08 07

FGS REacq 02 02

OBAD with Maneuver 20 20


SIGNIFICANT EVENTS:

Flash Report:

WFPC2 WF4 post-temperature reduction early results:
The first internal images after reducing the WFPC2 Replacement Heater
temperature set points on Tuesday look good. The WF4 CCD bias levels are
back in the 290 - 300 DN range and very close to normal again. Changes
in optical alignment are very small and in the expected range. All the
images so far look nominal.

 




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