We have used the ultraviolet all-sky imaging survey currently being
conducted by the Galaxy Evolution Explorer {GALEX} to identify for the
first time a rare population of low- redshift starbursts with properties
remarkably similar to high-redshift Lyman Break Galaxies. These compact
UV luminous galaxies {UVLGs} resemble Lyman Break Galaxies in terms of
size, UV luminosity, star-formation rate, surface brightness, mass,
metallicity, kinematics, dust content, and color. They have
characteristic ``ages'' {stellar mass/SFR} of only a few hundred Myr.
This population of galaxies is thus worthy of study in its own right and
as a sample of local analogs of Lyman Break Galaxies. We propose to
image a sample of the 9 nearest and brightest compact UVLGs in the
near-ultraviolet, near-infrared, and H-alpha using ACS. With these
images we will 1} characterize their structure and morphology, 2} look
for signs of interactions and mergers, 3} investigate the distribution
and propogation of star formation over varying time scales, and 4}
quantify the stellar populations and star formation history, in order to
determine whether a previous generation of stars formed long before the
current burst. These data will perfectly complement our existing
Spitzer, GALEX, and SDSS data, and will provide important information on
star- formation in the present-day universe as well as shed light on the
earliest major episodes of star formation in high-redshift galaxies.

We propose observations of the newly discovered extrasolar planet XO-2b
and its twin star XO-2. When combined with the transit light curve, the
FGS-derived parallax will constrain the stellar mass of the host star
XO-2. From the high signal-to-noise near-IR time series resulting from
NICMOS grism spectroscopy, we will refine the system parameters, in
particular radii of the star and planet. From the same data, we will
search for evidence of water vapor in the atmosphere via transmission
spectroscopy. Differential observations with NICMOS in the spectroscopic
mode will be used to search for the small spectral changes that occur
during planetary transits resulting from absorption of stellar light as
it passes through the planetary atmosphere. Water is an important
constituent, the detection of which would provide information on Oxygen,
and it has a convenient strong band well- positioned for NICMOS.

The purpose of this proposal is to monitor the dark current, read noise,
and shading profile for all three NICMOS detectors throughout the
duration of Cycle 15. This proposal is a slightly modified version of
proposal 10380 of cycle 13 and 9993 of cycle12 and is the same as Cycle
14. that we cut down some exposure time to make the observation fit
within 24 orbits.

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.

We propose to obtain F110W and F160W imaging of 10 z~2.4 submillimeter
galaxies {SMGs} whose optical redshifts have been confirmed by the
detection of millimeter CO and/or mid-infrared PAH emission. With the
4000A break falling within/between the two imaging filters, we will be
able to study these sources' spatially resolved stellar populations
{modulo extinction} in the rest-frame optical. SMGs' large luminosities
appear to be due largely to merger-triggered starbursts; high-resolution
NICMOS imaging will help us understand the stellar masses, mass ratios,
and other properties of the merger progenitors, valuable information in
the effort to model the mass assembly history of the universe.

We propose the continuation of our highly successful SNAPshot survey of
a sample of 125 very X-ray luminous clusters in the redshift range
0.3-0.7. As demonstrated by the 25 snapshots obtained so far in Cycle14
and Cycle15 these systems frequently exhibit strong gravitational
lensing as well as spectacular examples of violent galaxy interactions.
The proposed observations will provide important constraints on the
cluster mass distributions, the physical nature of galaxy-galaxy and
galaxy-gas interactions in cluster cores, and a set of optically bright,
lensed galaxies for further 8-10m spectroscopy. All of our primary
science goals require only the detection and characterization of
high-surface-brightness features and are thus achievable even at the
reduced sensitivity of WFPC2. Because of their high redshift and thus
compact angular scale our target clusters are less adversely affected by
the smaller field of view of WFPC2 than more nearby systems.
Acknowledging the broad community interest in this sample we waive our
data rights for these observations. Due to a clerical error at STScI our
approved Cycle15 SNAP program was barred from execution for 3 months and
only 6 observations have been performed to date - reinstating this SNAP
at Cycle16 priority is of paramount importance to reach meaningful
statistics.

The recent discovery of numerous transneptunian binaries {TNBs} opens a
window into dynamical conditions in the protoplanetary disk where they
formed as well as the history of subsequent events which sculpted the
outer Solar System and emplaced them onto their present day heliocentric
orbits. To date, at least 47 TNBs have been discovered, but only about a
dozen have had their mutual orbits and separate colors determined,
frustrating their use to investigate numerous important scientific
questions. The current shortage of data especially cripples scientific
investigations requiring statistical comparisons among the ensemble
characteristics. We propose to obtain sufficient astrometry and
photometry of 23 TNBs to compute their mutual orbits and system masses
and to determine separate primary and secondary colors, roughly tripling
the sample for which this information is known, as well as extending it
to include systems of two near-equal size bodies. To make the most
efficient possible use of HST, we will use a Monte Carlo technique to
optimally schedule our observations.

HSTARS:
11019 - GSAcq(2,1,2) Failed to RGA Hold (Gyro Control)
Upon acquisition of signal (AOS) at 283/16:00:07, the GSAcq(2,1,2)
scheduled at 283/15:48:45 - 15:56:49 had failed to RGA Hold due to a
Search Radius Limit Exceeded Error on FGS-2. 486 Status Buffer (ESB)
Dump completed at 283/16:04:00 showed one 486 ESB "a05" (FGS Coarse
Track failed-Search Radius Limit Exceeded) was received at 283/15:53:53.
Additional ESB 1805(x6)(T2G_MOVING_TARGET_DETECTED) was received.
Pre-acquisition OBAD1 attitude correction value not available due to
LOS. Pre-acq OBAD2 had (RSS) value of 14.58 arcseconds. Post-acq
OBAD/MAP had (RSS) value of 165.35 arcseconds.