Status Report

NASA Hubble Space Telescope Daily Report # 3683

By SpaceRef Editor
August 27, 2004
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science




ACS/HRC 10102

Rings of Uranus: Dynamics, Particle Properties and Shepherding Moons

Last year, our Uranian ring and moon observing program {GO-9823}
resulted in the discovery of two moons, S/2003 U 1 and S/2003 U 2.
We imaged two additional small moons, Ophelia and S/1986 U 10, that
had not been seen since the Voyager encounter of 1986. Furthermore,
our data show faint arcs and clumps orbiting within the rings, which
were not seen by Voyager and are completely unexpected. We employed
several "tricks" of the HRC to achieve this remarkable senstivity;
specifically, we used the CLEAR filter and oriented the images so
that the planet, though vastly overexposed, did not interfere with
the ring/moon region of interest to us. This allowed us to detect
25th-magnitude moons circling a 5th-magnitude planet. Now we propose
to complete the task by carrying out a comprehensive survey of the
system using the same techniques. Our goals are to recover the
moons, better discern their orbital elements, and learn more about
the dynamics of the ring clumps. In particular, we need to {1}
understand the long-term stability of S/2003 U 2, which orbits
perilously close to the larger moon Belinda; {2} complete our search
for moons, which was only ~ 50% complete last year, and {3} better
understand how the clumps and arcs within the ring system might
relate to nearby "shepherding" moons, seen or unseen. This program
is now a merger of two programs 10275 and 10102. The former is our
new program, whereas the latter is the second year of our three-year
program to study the light scattering properties of Uranus’s rings
as they approach their edge-on presentation in 2007.

ACS/HRC 10255

A Never Before Explored Phase Space: Resolving Close White Dwarf /
Red Dwarf Binaries

We propose an ACS Snapshot imaging survey to resolve a well-defined
sample of highly probable white dwarf plus red dwarf close binaries.
These candidates were selected from a search for white dwarfs with
infrared excess from the 2MASS database. They represent unresolved
systems {separations less than approximately 2" in the 2MASS images}
and are distributed over the whole sky. Our HST+ACS observations
will be sensitive to a separation range {1-20 AU} never before
probed by any means. The proposed study will be the first empirical
test of binary star parameters in the post-AGB phase, and cannot be
accomplished from the ground. By resolving as few as 20 of our ~100
targets with HST, we will be able to characterize the distribution
of orbital semi-major axes and secondary star masses.


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.


Tracing the History of Cosmic Expansion to z~2 with Type Ia

Type Ia supernovae {SNe Ia} provide the only direct evidence for an
accelerating universe, an extraordinary result that needs the most
rigorous test. The case for cosmic acceleration rests on the
observation that SNe Ia at z = 0.5 are about 0.25 mag fainter than
they would be in a universe without acceleration. A powerful and
straightforward way to assess the reliability of the SN Ia
measurement and the conceptual framework of its interpretation is to
look for cosmic deceleration at z 1. This would be a clear
signature of a mixed dark-matter and dark-energy universe.
Systematic errors in the SNe Ia result attributed to grey dust or
cosmic evolution of the SN Ia peak luminosity would not show this
change of sign. We have obtained a toehold on this putative “epoch
of deceleration” with SN 1997ff at z = 1.7, and 3 more at z 1
from our Cycle 11 program, all found and followed by HST. However, this is
too important a test to rest on just a few objects, anyone of which
could be subject to a lensed line-of-sight or misidentification. Here
we propose to extend our measurement with observations of twelve SNe
Ia in the range 1.0 < z < 1.5 or 6 such SNe Ia and 1 ultradistant SN
Ia at z = 2, that will be discovered as a byproduct from proposed
Treasury and DD programs. These objects will provide a much firmer
foundation for a conclusion that touches on important questions of
fundamental physics.

ACS/WFC 10216

Co-evolution of spheroids and black holes

The masses of the giant black holes in galaxies are correlated with
the luminosities, masses, and velocity dispersions of their host
spheroids. This empirical connection of phenomena on widely different
scales {from sub-parsec to kiloparsec} suggests that the evolution of
a galaxy and its central black hole are closely linked. We propose to
test various unified formation models, by measuring the cosmic
evolution of the black hole/spheroid relations, back to z=0.37 {a
lookback time of 4 Gyrs}. We will obtain 1-orbit ACS images of a
sample of 20 Seyfert 1 galaxies, for which we already have extensive
new ground-based measures of the black hole masses and the stellar
velocity dispersions. HST resolution is required for accurate
measurement of the nonstellar AGN continuum, and the luminosity and
effective radius of the bulge of each host galaxy. This will complete
the set of observables needed to map the co-evolution of spheroids and
black-holes. The proposed sample is the minimum required to make the
first measure of the black hole mass/bulge correlation and of the
fundamental plane for active galaxies outside the local Universe.

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


Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.) None

ROP: Updated CCS ESB Limit for SESBSLD = 10, Code d0c "Battery SOC
below first limit" @ 239/17:37Z (ROP DF-18A).

                          SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq               9                             9
FGS REacq               11                           11
FHST Update             6                            6  


Completed Battery 3 Capacity Test (OR 17259). Commanding to update
the Benchmark SOC and SOC Safing test limits and to restore the
nominal 6-battery FSW configuration with TRSWCC and Charge
Optimization was completed @ 239/17:46Z. Commanding to restore the
Battery Pressure test limits to their nominal values was completed
239/17:54Z (OR 17260). ESTR to BOT and powered off @ 239/09:41Z

SpaceRef staff editor.