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Daily 3690



 
 
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Old September 9th 04, 05:43 PM
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HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 3690

PERIOD COVERED: DOY 251

OBSERVATIONS SCHEDULED

ACS/HRC 10050

ACS Earth Flats

High signal sky flats will be obtained by observing the bright Earth
with the HRC and WFC. These observations will be used to verify the
accuracy of the flats currently used by the pipeline and will provide
a comparison with flats derived via other techniques: L-flats from
stellar observations, sky flats from stacked GO observations, and
internal flats using the calibration lamps. Weekly coronagraphic
monitoring is required to assess the changing position of the spots.

ACS/HRC 10182

Towards a Comprehensive Understanding of Type Ia Supernovae: The
Necessity of UV Observations

Type Ia supernovae {SNe Ia} are very important to many diverse areas
of astrophysics, from the chemical evolution of galaxies to
observational cosmology which led to the discovery of dark energy and
the accelerating Universe. However, the utility of SNe Ia as
cosmological probes depends on the degree of our understanding of SN
Ia physics, and various systematic effects such as cosmic chemical
evolution. At present, the progenitors of SNe Ia and the exact
explosion mechanisms are still poorly understood, as are evolutionary
effects on SN Ia peak luminosities. Since early-time UV spectra and
light curves of nearby SNe Ia can directly address these questions, we
propose an approach consisting of two observational components: {1}
Detailed studies of two very bright, young, nearby SNe Ia with HST UV
spectroscopy at 13 epochs within the first 1.5 months after discovery;
and {2} studies of correlations with luminosity for five somewhat more
distant Hubble-flow SNe Ia, for which relative luminosities can be
determined with precision, using 8 epochs of HST UV spectroscopy
and/or broad-band imaging. The HST data, along with extensive
ground-based optical to near-IR observations, will be analyzed with
state-of-the-art models to probe SN Ia explosion physics and constrain
the nature of the progenitors. The results will form the basis for the
next phase of precision cosmology measurements using SNe Ia, allowing
us to more fully capitalize on the substantial past {and future}
investments of time made with HST in observations of high-redshift SNe
Ia.

ACS/HRC 10199

The Most Massive Galaxies in the Universe: Double Trouble?

We are proposing an HST snapshot survey of 70 objects with velocity
dispersion larger than 350 km/s, selected from the Sloan Digital Sky
Survey. Potentially this sample contains the most massive galaxies in
the Universe. Some of these objects may be superpositions; HST imaging
is the key to determining if they are single and massive or if they
are two objects in projection. The objects which HST imaging shows to
be single objects are interesting because they potentially harbor the
most massive black holes, and because their existence places strong
constraints on galaxy formation models. When combined with ground
based data already in hand, the objects which HST imaging shows are
superpositions provide valuable information about interaction rates of
early-type galaxies as well as their dust content. They also constrain
the allowed parameter space for models of binary gravitational lenses
{such models are currently invoked to explain discrepancies in the
distribution of lensed image flux ratios and separations}.

ACS/HRC/WFC 10048

Stability of the ACS CCD: Flat fielding, Photometry, Geometry

This program will verify that the low frequency flat fielding, the
photometry, and the geometric distortion are stable in time and across
the field of view of the CCD detectors. A moderately crowded stellar
field, located ~6' West of the center of the cluster 47 Tuc, is
observed every three months with the WFC and HRC using the full suite
of broad and narrow band filters. The same field has been observed
during SMOV to derive low frequency corrections to the ground flats
and to create a master catalogue of positions and magnitudes from
dithered observations of the cluster. In Cycle 11, this field was
observed again using single pointings at various roll angles. The
positions and magnitudes of objects are used to monitor local and
large scale variations in the plate scale and the sensitivity of the
detectors. The Cycle 12 program will continue to monitor these effects
and will derive an independent measure of the detector CTE.

ACS/HRC/WFC 10061

CCD Daily Monitor

This program consists of basic tests to monitor, the read noise, the
development of hot pixels and test for any source of noise in ACS CCD
detectors. This programme will be executed once a day for the entire
lifetime of ACS.

ACS/SBC 10047

ACS UV Contamination Monitor

A standard star field {NGC6681} is observed every three months,
alternating between after and before annealing operations, through all
the ACS broad band UV filters. NGC6681 hosts several UV spectro -
photometric standard stars for which accurate spectra have been {and
will continue to be} measured with STIS. Two SBC dark current
exposures taken as the last exposure of each SBC sequence. Also, to
minimize SBS turn-on/turn-off cycles and in order to check the lab
flats for the SBC detector, internal observations using the deuterium
lamp with F125LP are being taken inflight, following the UV monitor
observations. The internal flats have been taken ~monthly since SMOV,
and the degradation of the lamp has been monitored. The total exposure
time to date is ~15 hours giving a total of 8600 counts/pixel. The
goal is 10, 000 counts/pixel such that the resulting pipeline flat has
uncertainties of ~1% due to poison counting statistics. Thus,
approximately 3 additional hours of observation are required.

ACS/WFC 10248

Current star formation in young, compact clusters in the Small
Magellanic Cloud

The Small Magellanic Cloud {SMC} offers a deep, resolved stellar
population that leverages fundamental parameters {metallicity, dust
content} with respect to the Milky Way and to its most studied
counterpart, the LMC. Its subsolar metallicity makes it the best
analog to the large majority of dwarf irregulars, and gives us the
possibility to study star formation and evolution in an environment
with the closest {available} resemblance to the early universe. Young,
compact clusters are ideal laboratories to investigate how these
fundamental differences affect star and cluster formation and
evolution. We are therefore, proposing, to use ACS and NICMOS to
perform a in depth study of the "resolved" stellar population in the
four youngest compact clusters in the SMC. The observations, spanning
the UV to the near-IR, will reach the subsolar domain, and will
address the following fundamental questions: Does the IMF follow the
universal Salpeter's law? Is mass segregation prevalent in the SMC
clusters as in LMC clusters? Is on-going star formation present, where
and how? What is the role of massive star feedback? The four proposed
clusters span an age range from 3-20 Myr, and sample spatially
different regions of the SMC. The synergy with NICMOS will permit full
characterization of existing pre main sequence stars, if detected.
This proposal is part of a coordinated HST and ground-based study of
the stellar history and star formation processes in the SMC.

FGS 9335

Masses of Pre-Main Sequence Binaries

We propose to continue to map the orbits of young star binaries in the
Taurus and Ophiuchus star forming regions. Our goal is to measure
their masses dynamically. This is important because there are still no
low mass young stars with reliably known masses so calculations of
their evolution to the main sequence are uncalibrated.

NIC1 10143

Ultracool companions to the nearest L dwarfs

We propose to conduct the most sensitive survey to date for low mass
companions to nearby L dwarfs. We will use NICMOS to image targets
drawn from a volume-complete sample of 70 L dwarfs within 20 parsecs.
The combination of infrared imaging and proximity will allow us to
search for T dwarf companions at separations as small as 1.6 AU. This
is crucial, since no ultracool binaries are currently known with
separations exceeding 15 AU. Only 10 dwarfs in this sample have
previous HST observations primarily at optical wavelengths. With the
increased sensitivity of our survey, we will provide the most
stringent test to date of brown dwarf models which envisage formation
as ejected stellar embryos. In addition, our observations will be
capable of detecting binaries with mass ratios as low as 0.3, and will
therefore also test the apparent preference for equal-mass ultracool
binaries. Finally, our observations offer the best prospect to date of
detecting companions significantly cooler than the coolest t dwarf
currently known.

NIC1 10208

NICMOS Differential Imaging Search for Planetary Mass Companions to
Nearby Young Brown Dwarfs

We propose to use the differential spectral imaging capability of
HST/NICMOS {NIC1} to search for planetary mass companions. We target
the twelve most nearby {within 30 pc}, isolated {no known close
companion}, and young { 1Gyr} brown dwarfs. All of them have spectral
type L and show signs of Lithium absorption, which clearly proves
their substellar nature and youth. Planetary mass companions with
masses down to 6 Jupiter masses, and at separations larger than 3 A.U.
are bright enough for a direct detection with HST/NICMOS using the
spectral differential imaging technique in two narrow-band filters
placed on and off molecular bands. The proposed project has the
potential to lead to the first direct detection of a planetary mass
object in orbit around a nearby brown dwarf.

NIC1 10247

Resolving a Binary System that Straddles the L/T Transition

We propose to make the first unequivocal resolved observation of a
brown dwarf binary system comprised of an L dwarf and a T dwarf. The
proposed observations will confirm the binarity of the system, measure
the physical separation of the two components, provide a robust
spectral type estimate for the T dwarf secondary, and enable the mass
ratio of the system to be determined. As a late-L/mid-T binary, the
components straddle the poorly understood "L/T transition" where a
brightening of T dwarfs at J-band is observed compared to the
comparatively warmer L dwarfs. In addition to testing theories for
this brightening, these data will put strong constraints on substellar
evolution and formation models.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration - CR Persistence Part 4

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 10177

Solar Systems In Formation: A NICMOS Coronagraphic Survey of
Protoplanetary and Debris Disks

Until recently, despite decades of concerted effort applied to
understanding the formation processes that gave birth to our solar
system, the detailed morphology of circumstellar material that must
eventually form planets has been virtually impossible to discern. The
advent of high contrast, coronagraphic imaging as implemented with the
instruments aboard HST has dramatically enhanced our understanding of
natal planetary system formation. Even so, only a handful of evolved
disks {~ 1 Myr and older} have been imaged and spatially resolved in
light scattered from their constituent grains. To elucidate the
physical processes and properties in potentially planet-forming
circumstellar disks, and to understand the nature and evolution of
their grains, a larger spatially resolved and photometrically reliable
sample of such systems must be observed. Thus, we propose a highly
sensitive circumstellar disk imaging survey of a well-defined and
carefully selected sample of YSOs {1-10 Myr T Tau and HAeBe stars} and
{ app 10 Myr} main sequence stars, to probe the posited epoch of
planetary system formation, and to provide this critically needed
imagery. Our resolved images will shed light on the spatial
distributions of the dust in these thermally emissive disks. In
combination with their long wavelength SEDs the physical properties of
the grains will be discerned, or constrained by our photometrically
accurate surface brightness sensitivity limits for faint disks which
elude detection. Our sample builds on the success of the exploratory
GTO 7233 program, using two-roll per orbit PSF-subtracted NICMOS
coronagraphy to provide the highest detection sensitivity to the
smallest disks around bright stars which can be imaged with HST. Our
sample will discriminate between proposed evolutionary scenarios while
providing a legacy of cataloged morphologies for interpreting mid- and
far-IR SEDs that the recently launched Spitzer Space Telescope will
deliver.

WFPC2 10071

WFPC2 CYCLE 12 Supplemental Darks Part 3/3

This dark calibration program obtains 3 dark frames every day to
provide data for monitoring and characterizing the evolution of hot
pixels.

WFPC2 10075

WFPC2 CYCLE 12 Intflat and Viflat Sweeps and Filter Rotation Anomaly
Monitor

Using intflat observations, this WFPC2 proposal is designed to monitor
the pixel-to-pixel flatfield response and provide a linearity check.
The intflat sequences, to be done once during the year, are similar to
those from the Cycle 11 program 9597. The images will provide a backup
database in the event of complete failure of the visflat lamp as well
as allow monitoring of the gain ratios. The sweep is a complete set of
internal flats, cycling through both shutter blades and both gains.
The linearity test consists of a series of intflats in F555W, in each
gain and each shutter. As in Cycle 11, we plan to continue to take
extra visflat, intflat, and earthflat exposures to test the
repeatability of filter wheel motions.

FLIGHT OPERATIONS SUMMARY:

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

HSTAR 9530: GS Acquisition (1,2,1) @ 252/05:59:32Z resulted in FL
backup (1,0,1) due to SSLE on FGS 1. Following FHST Map showed
vehicle error of 1.176, -6.823, and -4.179 arcsec. Both FHST FM
Updates prior to the acquisition passed with low vehicle error. Under
investigation.

COMPLETED OPS REQs: None

OPS NOTES EXECUTED: None

SCHEDULED SUCCESSFUL FAILURE TIMES
FGS Gsacq 16 16
FGS Reacq 3 3
FHST Update 18 18
LOSS of LOCK

SIGNIFICANT EVENTS: None


 




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