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14 May 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT       # 3362

PERIOD COVERED: DOY 133

Part 1 of 3

OBSERVATIONS SCHEDULED

NICMOS 8791

NICMOS Post-SAA calibration - CR Persistence Part 2

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.

WFPC2 9334

Dynamical Masses of White Dwarfs from Resolved Sirius-Like Binaries

In Cycle 8 we initiated a WFPC2 snapshot survey for resolved,
``Sirius-like'' systems containing hot white-dwarf companions of
cooler main-sequence stars. Out of 17 systems observed to date, 8
have been resolved with WFPC2 by using UV filters. Two of the
resolved systems---56 Persei and Zeta Cygni---have predicted or known
orbital periods short enough that dynamical masses can be determined
for the white dwarfs within reasonable times. These would thus add to
the extremely small number of white dwarfs presently having
accurately and directly measured masses. We propose to image them
annually in the UV with WFPC2. In addition, we will observe Zeta Cyg
with FGS in order to measure the absolute motion of the optical
component, needed for the mass solution. We also propose to observe
Sirius itself with WFPC2 over the next 3 Cycles. The resulting
astrometric data will not only greatly improve the precision of the
binary orbit and the dynamical mass measurements for both the
main-sequence and white-dwarf components, but will also test
definitively for the claimed presence of a third body in this famous
system. 

GO 9367

Unique Opportunities to Search for the Optical Counterparts to High-Z
Damped LyAlpha Systems

The galaxies responsible for damped LyAlpha absorption in QSO spectra
are difficult to observe against the strong background QSO emission.
We propose to detect even low luminosity galaxies associated with QSO
absorption line systems out to redshifts as high as z = 1.8 by
observing them in the shadow cast by an even higher redshift damped
LyAlpha absorber. As a result the galaxy will be observed free of
contamination by the background AGN and of the uncertainties which
arise when image processing techniques are required to remove the AGN
emission. We propose two approaches. In the first we will attempt to
detect a z = 1.8634 system seen in the optical spectrum of a high-z
BL Lac object in the shadow of two higher-redshift systems seen in
the same optical spectrum. In the second only the higher redshift
shadowing LyAlpha system is seen in the optical spectrum and the
presence of the lower- redshift systems at z = 0.713 and z = 1.0466
are inferred from the presence of strong MgII, SiII and FeII
absorption lines. 

ACS/HRC 9391

High-Resolution Imaging of Pluto's Surface

We will collect a series of observations with the ACS/HRC from which
we will derive a two-color global map of Pluto's surface. We will
image Pluto at F435W and F555W, wavelengths that have been
extensively studied from the ground over the past 50 years. The maps
will provide albedos with accurate error determinations down to 52
degrees South latitude. These observations will provide a second
epoch of HST mapping of the active surface of Pluto as it continues
to recede from the Sun and will provide an important context for
other detailed studies of Pluto.

NICMOS/STIS CCD 9405

The Origin of Gamma-Ray Bursts

The rapid and accurate localization of gamma-ray bursts {GRBs}
promised by a working HETE-2 during the coming year may well
revolutionize our ability to study these enigmatic, highly luminous
transients. We propose a program of HST and Chandra observations to
capitalize on this extraordinary opportunity. We will perform some of
the most stringent tests yet of the standard model, in which GRBs
represent collimated relativistic outflows from collapsing massive
stars. NICMOS imaging and STIS CCD spectroscopy will detect broad
atomic features of supernovae underlying GRB optical transients, at
luminosities more than three times fainter than SN 1998bw. UV,
optical, and X-ray spectroscopy will be used to study the local ISM
around the GRB. Chandra spectroscopy will investigate whether the GRB
X-ray lines are from metals freshly ripped from the stellar core by
the GRB. HST and CTIO infra-red imaging of the GRBs and their hosts
will be used to determine whether `dark' bursts are the product of
unusually strong local extinction; imaging studies may for the first
time locate the hosts of `short' GRBs. Our early polarimetry and
late-time broadband imaging will further test physical models of the
relativistic blast wave that produces the bright GRB afterglow, and
will provide unique insight into the influence of the GRB environment
on the afterglow. 

ACS 9480

Cosmic Shear With ACS Pure Parallels

Small distortions in the shapes of background galaxies by foreground
mass provide a powerful method of directly measuring the amount and
distribution of dark matter.  Several groups have recently detected
this weak lensing by large-scale structure, also called cosmic shear.
The high resolution and sensitivity of HST/ACS provide a unique
opportunity to measure cosmic shear accurately on small scales. Using
260 parallel orbits in Sloan textiti {F775W} we will measure for the
first time: beginlistosetlength sep0cm setlengthemsep0cm setlength
opsep0cm em the cosmic shear variance on scales <0.7 arcmin, em the
skewness of the shear distribution, and em the magnification effect.
endlist Our measurements will determine the amplitude of the mass
power spectrum sigma_8Omega_m^0.5, with signal-to-noise {s/n} ~ 20,
and the mass density Omega_m with s/n=4. They will be done at small
angular scales where non-linear effects dominate the power spectrum,
providing a test of the gravitational instability paradigm for
structure formation. Measurements on these scales are not possible
from the ground, because of the systematic effects induced by PSF
smearing from seeing. Having many independent lines of sight reduces
the uncertainty due to cosmic variance, making parallel observations
ideal. 

 - Continued -

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