Daily Report # 4388

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 # 4388

PERIOD COVERED: UT June 20, 2007 (DOY 171)

OBSERVATIONS SCHEDULED

WFPC2 10922

Searching for Signs of a Double Generation of Stars in Galactic Globular
Clusters

This proposal has been stimulated by new findings of ours that may have a
strong impact on the interpretation of globular cluster {GC} stellar
populations. In 2004, based on HST data, we have found that the main
sequence of the Galactic globular cluster Omega Centauri is split into two
sequences; spectroscopic analysis has shown that the only isochrones which
are able to fit the combination of color and metallicity of the bluest of
the two sequences were younger and greatly enriched in helium. A number of
observational facts, and theoretical evidence suggest that our results on
Omega Centauri might represent an extreme case of a phenomenon which has
also been at work in other GCs. We have selected the most promising GCs to
find out whether this hypothesis is correct, and make a strong case for its
likelihood and the value of pursuing it.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

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 10893

Sweeping Away the Dust: Reliable Dark Energy with an Infrared Hubble Diagram

We propose building a high-z Hubble Diagram using type Ia supernovae
observed in the infrared rest-frame J-band. The infrared has a number of
exceptional properties. The effect of dust extinction is minimal, reducing a
major systematic tha may be biasing dark energy measurements. Also, recent
work indicates that type Ia supernovae are true standard candles in the
infrared meaning that our Hubble diagram will be resistant to possible
evolution in the Phillips relation over cosmic time. High signal-to-noise
measurements of 9 type Ia events at z~0.4 will be compared with an
independent optical Hubble diagram from the ESSENCE project to test for a
shift in the derived dark energy equation of state due to a systematic bias.
Because of the bright sky background, H-band photometry of z~0.4 supernovae
is not feasible from the ground. Only the superb image quality and dark
infrared sky seen by HST makes this test possible. This experiment may also
lead to a better, more reliable way of mapping the expansion history of the
universe with the Joint Dark Energy Mission.

NIC3 10504

Characterizing the Sources Responsible for Cosmic Reionization

Our group has demonstrated the role that massive clusters, acting as
powerful cosmic lenses, can play in constraining the abundance and
properties of low-luminosity star- forming sources beyond z~6; such sources
are thought to be responsible for ending cosmic reionization. The large
magnification possible in the critical regions of well- constrained clusters
brings sources into view that lie at or beyond the limits of conventional
exposures such as the UDF, as well as those in imaging surveys being
undertaken with IRAC onboard Spitzer. We have shown that the combination of
HST and Spitzer is particularly effective in delivering the physical
properties of these distant sources, constraining their mass, age and past
star formation history. Indirectly, we therefore gain a valuable glimpse to
yet earlier epochs. Recognizing the result {and limitations} of the UDF
exposure, we propose a systematic search through 6 lensing clusters with ACS
and NICMOS for further z~6-7 sources in conjunction with existing deep IRAC
data. Our survey will mitigate cosmic variance and extend the search both to
lower luminosities and, by virtue of the NICMOS/IRAC combination, to higher
redshift. The goal is to count and characterize representative sources at
z~6-10 and to delineate the redshift range of activity for the planning of
future observations.

WFPC2 10915

ACS Nearby Galaxy Survey

Existing HST observations of nearby galaxies comprise a sparse and highly
non-uniform archive, making comprehensive comparative studies among galaxies
essentially impossible. We propose to secure HST's lasting impact on the
study of nearby galaxies by undertaking a systematic, complete, and
carefully crafted imaging survey of ALL galaxies in the Local Universe
outside the Local Group. The resulting images will allow unprecedented
measurements of: {1} the star formation history {SFH} of a 100 Mpc^3 volume
of the Universe with a time resolution of Delta[log{t}]=0.25; {2}
correlations between spatially resolved SFHs and environment; {3} the
structure and properties of thick disks and stellar halos; and {4} the color
distributions, sizes, and specific frequencies of globular and disk clusters
as a function of galaxy mass and environment. To reach these goals, we will
use a combination of wide-field tiling and pointed deep imaging to obtain
uniform data on all 72 galaxies within a volume-limited sample extending to
~3.5 Mpc, with an extension to the M81 group. For each galaxy, the
wide-field imaging will cover out to ~1.5 times the optical radius and will
reach photometric depths of at least 2 magnitudes below the tip of the red
giant branch throughout the limits of the survey volume. One additional deep
pointing per galaxy will reach SNR~10 for red clump stars, sufficient to
recover the ancient SFH from the color-magnitude diagram. This proposal will
produce photometric information for ~100 million stars {comparable to the
number in the SDSS survey} and uniform multi- color images of half a square
degree of sky. The resulting archive will establish the fundamental optical
database for nearby galaxies, in preparation for the shift of high-
resolution imaging to the near-infrared.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST:

18104-0 - MSS/CSS Initialization Test#39 for day 171
18107-0 - TDRSS Orbital Elements Update @171/1208z
18054-0 - Preview KF Sun Vector Data via Telemetry Diags

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL

FGS GSacq 06 06
FGS REacq 08 08
OBAD with Maneuver 28 28

SIGNIFICANT EVENTS:

Evaluation of Universal Kalman Filter performance continued. Details follow.

The KF was halted at 161/17:27. It was reinitialized with the MSS and CSS
sensor inputs enabled at 171/17:30 (OR 18104-0). All UKF parameters showed
nominal operation. The test was to monitor the convergence of the filter
after restart with the MSS and CSS sensor inputs enabled during a vehicle
maneuver and during a fast changing B-field (M_C_IVF, Test #5). The filter
will remain in the MSS/CSS configuration until tomorrow when additional
convergence testing is executed.