Daily #4101

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4101

PERIOD COVERED: UT April 26, 2006 (DOY 116)

OBSERVATIONS SCHEDULED

ACS/HRC/WFC 10758

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This programme will be
for the entire lifetime of ACS. Changes from cycle 13:- The default
gain for WFC is 2 e-/DN. As before bias frames will be collected for
both gain 1 and gain 2. Dark frames are acquired using the default
gain {2}. This program cover the period May, 31 2006- Oct, 1-2006. The
first half of the program has a different proposal number: 10729.

ACS/WFC 10505

The Onset of Star Formation in the Universe: Constraints from Nearby
Isolated Dwarf Galaxies.

The details of the early star formation histories of tiny dwarf
galaxies can shed light on the role in galaxy formation of the
reionization which occured at high redshift. Isolated dwarfs are ideal
probes since their evolution is not complicated by environmental
effects owing to the vicinity of the Milky Way and M31. In addition,
dwarf galaxies are the most common type of galaxies, and potentially
the building blocks of larger galaxies. Since we can date the oldest
stars in them, their study represents a complementary approach to the
study of the formation and evolution of galaxies through high-z
observations. We propose to use the ACS to obtain a homogeneus dataset
of high-quality photometry, down to the old {13 Gyr} main-sequence
turnoffs, for a representative sample of 4 isolated Local Group dwarf
galaxies. These data are essential to unambiguously determine their
early star formation histories, through comparison with synthetic
color-magnitude diagrams, and using the constraints provided by their
variable stars. Parallel WFPC2 observations of their halos will allow
us to reveal the actual nature of their stellar population gradients,
providing important aditional constraints on their evolution. The
proposed observations are being complemented with ground-based
spectroscopy, to obtain metallicity and kinematic information. The
observations requested here, which must reach M_I=+3.5 {I=27.5- 28.2}
with S/N=10 in crowded systems, can only be achieved with HST using
ACS, and won't be possible with planned ground- or space-based
facilities such as JWST. Based on deep WFPC2 observations and ACS
image simulations, our team has designed an observational strategy
which carefully considers the optimal filter combination, the
necessary photometry depth and the effects of stellar crowding.

ACS/WFC 10626

A Snapshot Survey of Brightest Cluster Galaxies and Strong Lensing to
z = 0.9

We propose an ACS/WFC snapshot survey of the cores of 150 rich galaxy
clusters at 0.3 z 0.9 from the Red Sequence Cluster Survey {RCS}.
An examination of the galaxian light in the brightest cluster
galaxies, coupled with a statistical analysis of the strong-lensing
properties of the sample, will allow us to contrain the evolution of
both the baryonic and dark mass in cluster cores, over an
unprecedented redshift range and sample size. In detail, we will use
the high- resolution ACS images to measure the metric {10 kpc/h}
luminosity and morphological disturbances around the brightest
clusters galaxies, in order to calibrate their accretion history in
comparison to recent detailed simulations of structure formation in
cluster cores. These images will also yield a well-defined sample of
arcs formed by strong lensing by these clusters; the frequency and
detailed distribution {size, multiplicity, redshifts} of these strong
lens systems sets strong constraints on the total mass content {and
its structure} in the centers of the clusters. These data will also be
invaluable in the study of the morphological evolution and properties
of cluster galaxies over a significant redshift range. These analyses
will be supported by extensive ongoing optical and near-infrared
imaging, and optical spectroscopy at Magellan, VLT and Gemini
telescopes, as well as host of smaller facilities.

S/C 4974

TRTTEST

The Transcient Response Test is for the periodic performance
monitoring of the FGS 2R servo A mechanism.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:
10242 - NICMOS STB 740 @ 111/20:08:02z

COMPLETED OPS REQUEST:
17734-0 - TRT Test #11 @ 116/13:52:46z
17695-2 - Monitor VehConLaw.Integral Path Data via TMDIAG Slot 0 @ 116/13:59z
17737-0 - BCT Prep: Adjust VTFE to K1L4 @ 116/15:15:55z


COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 08 08
FGS REacq 04 04
OBAD with Maneuver 26 26

SIGNIFICANT EVENTS:

Flash Report (TRTT)

The Transient Response Trending Test (TRTT) was completed successfully
this morning via Ops Request 17734, beginning at 116/11:50. The test
was nominal. The first guide star acquisition after the test, at
15:09, was successful.