NASA Hubble Space Telescope Daily Report #3868

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT       # 3868

PERIOD COVERED: DOY 145

OBSERVATIONS SCHEDULED

ACS/HRC 10165

Determination of orbits and colors for two new binaries in the Koronis
asteroid family

We propose to measure color and orbital properties of two asteroid
binaries in the Koronis family discovered in our SNAP-9747 survey. The
best previously studied asteroid binary system, Ida/Dactyl, is also in
the Koronis family. Differential space weathering measured on the Ida
and Dactyl surfaces has been a powerful constraint on models of
satellite formation mechanisms and satellite survivability. HST offers
the unique opportunity for similar measurements of these much smaller,
main-belt binaries. The new satellites are believed to have formed
through different collisional mechanisms than Ida/Dactyl. Further,
with a set of 4 relative position measurements for each of the two
systems, added to the discovery snapshots, we will determine and
compare the densities of the primaries with Ida {a large, 31.5 km,
asteroid with density 2.6+-0.5 g/cm^3, measured by the Galileo flyby}.
In contrast, {17246} and {22899} are 4.5 km bodies that are likely to
have been restructured since the family-forming event by subsequent
collisions. As all are members of the same family, differences in
density would constrain bulk composition and internal structure {e.g.
shard vs. rubble-pile}. Hence, these measurements are likely to
further elucidate the mechanisms for formation of satellites.

ACS/HRC/WFC 10389

ACS CCDs daily monitor – Cycle 13 – Part 2

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.

ACS/HRC/WFC 10399

Accurate and Robust Calibration of the Extragalactic Distance Scale
with the Maser Galaxy NGC4258 II

The extragalactic distance scale {EDS} is defined by a comparison of
Cepheid Period-Luminosity {PL} relations for nearby galaxies and the
LMC, whose uncertain distance is thereby the SOLE anchor. Studies of
masers orbiting the central black hole in NGC4258 have provided the
most accurate extragalactic distance ever {7.2+/-0.5 Mpc}, and new
radio data and analysis techniques will reduce the uncertainty to < 3.5% {0.07 mag} by 2005. Since this distance is well determined and based on geometric arguments, NGC4258 can provide a much needed new anchor for the EDS. Ultimately, the combination of an independent measurement of H0 and measurements of CMB fluctuations {e.g., WMAP} can be used to directly constrain cosmological parameters including the equation of state of dark energy. In our Cycle 12 proposal, we defined a program spanning two cycles. The Cycle 12 portion was accepted. We have acquired WFC images and are constructing well sampled PL relations in 3 colors {BVI}. The purpose of the Cycle 13 observations is to address systematic sources of error and is crucial for the success of the entire program. To disentangle the effects of reddening and metallicity, and to characterize the effects of blending, we require 50 orbits to obtain H-band photometry {NICMOS/NIC2} and high resolution images {ACS/HRC}.

ACS/WFC 10235

Dark vs. luminous matter in the CenA/M83 galaxy complex

The distribution of dark vs. luminous matter on scales of 0.1-1.0 Mpc
remains poorly understood. For a nearby group, the total mass can be
determined from the radius of “the zero-velocity surface”, which
separates the group from the general Hubble flow. This new method
requires the measurement of accurate distances and radial velocities
of galaxies around the group, but gives total mass estimates
independent of assumptions about the state of relaxation or orbital
characteristics. The mass pertains to the group at the full scale to
which it is bound. Upon application in several nearest groups, the
method yields mass estimates in agreement with the sum of the virial
masses of subcomponents. However, the typical total M/L ratio for the
nearby groups of ~30 Mo/Lo implies a local mean density of matter
which is only 1/7 the canonical global density . The nearby complex of
galaxies around Cen A and M83 resembles our Local Group by the
dumb-bell concentration of objects around a pair of dominant galaxies.
Accurate distances have been acquired recently for ~20 group members
by the TRGB method using HST. We will measure TRGB distances to the 17
remaining galaxies in the region. These observations will constrain
the dynamical state of the halo surrounding the nearest giant E-galaxy
Cen A, providing a comparison with the halos of the nearest spirals.

FGS 10432

Precise Distances to Nearby Planetary Nebulae

We propose to carry out astrometry with the FGS to obtain accurate and
precise distances to four nearby planetary nebulae. In 1992, Cahn et
al. noted that “The distances to Galactic planetary nebulae remain a
serious, if not THE most serious, problem in the field, despite
decades of study.” Twelve years later, the same statement still
applies. Because the distances to planetary nebulae are so uncertain,
our understanding of their masses, luminosities, scale height, birth
rate, and evolutionary state is severely limited. To help remedy this
problem, HST astrometry can guarantee parallaxes with half the error
of any other available approach. These data, when combined with
parallax measurements from the USNO, will improve distance
measurements by more than a factor of two, producing more accurate
distances with uncertainties that are of the order of ~6%. Lastly,
most planetary nebula distance scales in the literature are
statistical. They require several anchor points of known distance in
order to calibrate their zero point. Our program will provide “gold
standard” anchor points by the end of 2006, a decade before any
anticipated results from future space astrometry missions.

NIC3 10150

NICMOS observations of A1689

The potential of galaxy clusters as “cosmic telescopes” has been
known for a long time, but practical results in the pre-ACS era have
been scarce due to two main problems: the uncertainty in determining
the magnification distribution of the cluster {the “optics” of the
instrument} and the presence of numerous bright cluster galaxies which
cover the field of view and hinder the detection of background
galaxies. We have developed techniques to solve these two problems
working with our ACS observations of A1689, the most powerful lens in
the sky, and for the first time we have been able to determine the
“specifications” of a cosmic telescope with a useful level of
precision, thanks to the detection and identification of more than 100
multiple images with reliable redshift information. We propose to
observe the high magnification region in the A1689 field in the F110W
band with a 3×3 mosaic of NIC3 pointings; the resulting image will
reach a lens-corrected limiting magnitudes of 29.5 for point sources,
surpassing in depth the UDF NICMOS observations and providing an
unique dataset with multiple scientific returns.

NIC3/ACS/WFC 10404

The Nature of Protocluster Galaxies at z=2.16: Morphology-Density and
Color- Magnitude Relations

To establish the epoch when galaxy environment manifests itself as a
large-scale evolutionary process, we propose to extend the study of
galaxy colors and morphologies to a protocluster at z=2.16. Here the
universe is only 3 Gyrs old and significant differences are expected
between scenarios favoring a morphology- radius relation over a
morphology-density relation. In addition, because the fractional age
differences among cluster galaxies are larger, study of the color-
magnitude relation provides considerable leverage for determining the
epoch of early-type galaxy formation. To facilitate direct comparison
to studies at lower redshift, one must probe the same rest-frame
wavelengths with high photometric accuracy and at similar physical
scales. Its near-infrared photometric stability {low, constant
background} and ability to image large areas of sky at high angular-
resolution {compared to adaptive optics} makes HST/NICMOS ideal for
this program. Six pointings of NICMOS camera 3 will result in
rest-frame optical, high resolution images of 16 confirmed
protocluster members, and an additional 60 candidate protocluster
members including 29 EROs. These galaxies were selected with a variety
of techniques and span a range of projected radii within the
protocluster. The proposed observations constitute a unique
opportunity to extend the study of galaxies in overdense regions to an
early time in cosmic history.

NICMOS 8790

NICMOS Post-SAA calibration – CR Persistence Part 1.

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.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

9831 – ReAcq(2,1,2) requires three attempts to achieve FL-DV @
136/08:57:49z OTA SE review of PTAS processing reveals that
ReAcq(2,1,2) at 136/08:57:49 required three attempts to achieve FL-DV
on FGS2 due to scan step limit exceeded. The ReAcq was ultimately
successful.

9832 – ReAcq(1,2,2) requires two entries into CT @ 137/16:59:28z OTA
SE review of PTAS processing revealed that ReAcq(1,2,2) at
137/16:59:28 required two entries into Coarse Track on FGS1 before
achieving CT-DV.

9833 – GSAcq(2,1,1) requires two entries into CT @ 140/18:06:18z OTA
SE review of PTAS processing revealed that GSAcq(2,1,1) at
140/18:06:18 required two entries into Coarse Track on FGS2 before
achieving CT-DV.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                              SCHEDULED     SUCCESSFUL    FAILURE TIMES 
 FGS Gsacq                    11                     11 
 FGS Reacq                    05                     05 
 FHST Update                  17                    17 
 LOSS of LOCK 

SIGNIFICANT EVENTS:  (None)