Daily Report # 4366

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 # 4366

PERIOD COVERED: UT May 18,19,20, 2007 (DOY 138,139,140)

OBSERVATIONS SCHEDULED

WFPC2 11079

Treasury Imaging of Star Forming Regions in the Local Group: Complementing
the GALEX and NOAO Surveys

We propose to use WFPC2 to image the most interesting star-forming regions
in the Local Group galaxies, to resolve their young stellar populations. We
will use a set of filters including F170W, which is critical to detect and
characterize the most massive stars, to whose hot temperatures colors at
longer wavelengths are not sensitive. WFPC2's field of view ideally matches
the typical size of the star-forming regions, and its spatial resolution
allows us to measure indvidual stars, given the proximity of these galaxies.
The resulting H- R diagrams will enable studies of star-formation properties
in these regions, which cover largely differing metallicities {a factor of
17, compared to the factor of 4 explored so far} and characteristics. The
results will further our understanding of the star-formation process, of the
interplay between massive stars and environment, the properties of dust, and
will provide the key to interpret integrated measurements of star-formation
indicators {UV, IR, Halpha} available for several hundreds more distant
galaxies. Our recent deep surveys of these galaxies with GALEX {FUV, NUV}
and ground-based imaging {UBVRI, Halpha, [OIII] and [SII]} provided the
identification of the most relevant SF sites. In addition to our scientific
analysis, we will provide catalogs of HST photometry in 6 bands, matched
corollary ground-based data, and UV, Halpha and IR integrated measurements
of the associations, for comparison of integrated star-formation indices to
the resolved populations. We envisage an EPO component.

WFPC2 10903

Resolving the LMC Microlensing Puzzle: Where are the Lensing Objects?

We are requesting 12 HST orbits to continue to investigate the nature of the
population that gives rise to the microlensing seen towards the LMC. This
proposal builds on the cycle 14 HST program {10583} and will complement the
study with 12 yet-to-be discovered microlensing candidates from Fall 2006.
Our SuperMacho project is an ongoing ground- based survey on the CTIO 4m
that has demonstrated the ability to detect LMC microlensing events via
frame subtraction. The combination of high angular resolution and
photometric accuracy with HST will allow us to 1} confrim that the detected
flux excursions arise from LMC stars, rather than background supernovae or
AGN, and 2} obtain reliable baseline flux measurements for the objects in
their unlensed state. This latter measurement in important in determining
the microlensing optical depth towards the LMC.

WFPC2 10896

An Efficient ACS Coronagraphic Survey for Debris Disks around Nearby Stars

We propose to finish our Cycle 11 optical survey for nearby debris disks
using the ACS/HRC coronagraph. Out of 43 orbits originally proposed for the
survey, 23 orbits were allocated, leading to a survey of 22 stars, from
which two new debris disks were imaged for the first time. Our analysis of
the initial survey gives an empirical estimate for the detection rate of
debris disks relative to heliocentric distance and dust optical depth. Our
target list for Cycle 15 is now optimized to yield more frequent disk
detections. Likewise our observing strategy is improved to maximize
sensitivity per telescope orbit allocated. Therefore we present the most
efficient survey possible. The scientific motivation is to obtain scattered
light images of previously unresolved debris disks to determine their
viewing geometry and physical architecture, both of which may characterize
the underlying planetary system. We choose 25 debris disk targets for which
we predict a detection rate of 25% ? 5%. Four targets have extrasolar
planets from which the viewing geometry revealed by a disk detection will
resolve the v sin{i} ambiguity in the planet masses. These targets present
the remarkable opportunity of finally seeing a debris disk in system with
known planets.

NIC1 10889

The Nature of the Halos and Thick Disks of Spiral Galaxies

We propose to resolve the extra-planar stellar populations of the thick
disks and halos of seven nearby, massive, edge-on galaxies using ACS,
NICMOS, and WFPC2 in parallel. These observations will provide accurate star
counts and color-magnitude diagrams 1.5 magnitudes below the tip of the Red
Giant Branch sampled along the two principal axes and one intermediate axis
of each galaxy. We will measure the metallicity distribution functions and
stellar density profiles from star counts down to very low average surface
brightnesses, equivalent to ~32 V-mag per square arcsec. These observations
will provide the definitive HST study of extra-planar stellar populations of
spiral galaxies. Our targets cover a range in galaxy mass, luminosity, and
morphology and as function of these galaxy properties we will provide: - The
first systematic study of the radial and isophotal shapes of the diffuse
stellar halos of spiral galaxies - The most detailed comparative study to
date of thick disk morphologies and stellar populations - A comprehensive
analysis of halo and thick disk metallicity distributions as a function of
galaxy type and position within the galaxy. - A sensitive search for tidal
streams - The first opportunity to directly relate globular cluster systems
to their field stellar population We will use these fossil records of the
galaxy assembly process preserved in the old stellar populations to test
halo and thick disk formation models within the hierarchical galaxy
formation scheme. We will test LambdaCDM predictions on sub-galactic scales,
where it is difficult to test using CMB and galaxy redshift surveys, and
where it faces its most serious difficulties.

WFPC2 10877

A Snapshot Survey of the Sites of Recent, Nearby Supernovae

During the past few years, robotic {or nearly robotic} searches for
supernovae {SNe}, most notably our Lick Observatory Supernova Search {LOSS},
have found hundreds of SNe, many of them in quite nearby galaxies {cz 4000
km/s}. Most of the objects were discovered before maximum brightness, and
have follow-up photometry and spectroscopy; they include some of the
best-studied SNe to date. We propose to conduct a snapshot imaging survey of
the sites of some of these nearby objects, to obtain late-time photometry
that {through the shape of the light and color curves} will help reveal the
origin of their lingering energy. The images will also provide
high-resolution information on the local environments of SNe that are far
superior to what we can procure from the ground. For example, we will obtain
color-color and color-magnitude diagrams of stars in these SN sites, to
determine the SN progenitor masses and constraints on the reddening.
Recovery of the SNe in the new HST images will also allow us to actually
pinpoint their progenitor stars in cases where pre- explosion images exist
in the HST archive. This proposal is an extension of our successful Cycle 13
snapshot survey with ACS. It is complementary to our Cycle 15 archival
proposal, which is a continuation of our long-standing program to use
existing HST images to glean information about SN environments.

WFPC2 10870

The Ring Plane Crossings of Uranus in 2007

The rings of Uranus turn edge-on to Earth in May and August 2007. In
between, we will have a rare opportunity to see the unlit face of the rings.
With the nine optically thick rings essentialy invisible, we will observe
features and phenomena that are normally lost in their glare. We will use
this opportunity to search thoroughly for the embedded "shepherd" moons long
believed to confine the edges of the rings, setting a mass limit roughly 10
times smaller than that of the smallest shepherd currently known, Cordelia.
We will measure the vertical thicknesses of the rings and study the faint
dust belts only known to exist from a single Voyager image. We will also
study the colors of the newly-discovered faint, outer rings; recent evidence
suggests that one ring is red and the other blue, implying that each ring is
dominated by a different set of physical processes. We will employ near-
edge-on photometry from 2006 and 2007 to derive the particle filling factor
within the rings, to observe how ring epsilon responds to the "traffic jam"
as particles pass through its narrowest point, and to test the latest models
for preserving eccentricities and apse alignment within the rings. Moreover,
this data set will allow us to continue monitoring the motions of the inner
moons, which have been found to show possibly chaotic orbital variations; by
nearly doubling the time span of the existing ACS astrometry, the details of
the variations will become much clearer.

ACS/SBC 10864

Mapping the Gaseous Content of Protoplanetary and Young Planetary Systems
with ACS

One of the key problems in planetary system formation is understanding how
rapidly, and over what time interval Jovian planets can form. Dust in the
protoplanetary disk is critical in planetesimal formation, but it is the gas
which produces giant planets, and which is essential for their migration.
However, compared to data on the circumstellar dust, information on the gas
component is sparse, especially in the planet-formation zone. This severely
limits our ability to put observational constraints on giant planet
formation, except to note that the process must be largely complete by 12
Myr, given the paucity of Herbig Ae or classical T Tauri stars older than
10-12 Myr. In the FUV, photo-excited molecular hydrogen transitions have the
requisite contrast to the stellar photosphere, accretion shock, and
reflection nebulosity, and can be traced 50-100 AU from the exciting stars
in both envelopes and outflow cavities and protoplanetary disks. Central
disk cavities, an expected consequence of planet formation, larger than 0.1"
are directly detectable in HST FUV spectra, while smaller cavities may be
detected by comparison with protoplanetary disks which are still accreting
onto their stars. We propose augmenting existing HST coronagraphic imagery
of 6 Herbig Fe and T Tauri disks with ACS Solar-Blind Channel Lyman alpha
imagery and slitless spectroscopy simultaneously sampling the disk in
molecular hydrogen and small-grain reflection nebulosity. These data will be
used to quantify the amount of vertical stratification in these disks, to
map the mass-loss geometry from the star, and to determine whether removal
of molecular material preceeds, lags, or is contemporary with clearing of
the dust.

ACS/SBC 10862

Comprehensive Auroral Imaging of Jupiter and Saturn during the International
Heliophysical Year

A comprehensive set of observations of the auroral emissions from Jupiter
and Saturn is proposed for the International Heliophysical Year in 2007, a
unique period of especially concentrated measurements of space physics
phenomena throughout the solar system. We propose to determine the physical
relationship of the various auroral processes at Jupiter and Saturn with
conditions in the solar wind at each planet. This can be accomplished with
campaigns of observations, with a sampling interval not to exceed one day,
covering at least one solar rotation. The solar wind plasma density
approaching Jupiter will be measured by the New Horizons spacecraft, and a
separate campaign near opposition in May 2007 will determine the effect of
large-scale variations in the interplanetary magnetic field {IMF} on the
Jovian aurora by extrapolation from near-Earth solar wind measurements. A
similar Saturn campaign near opposition in Jan. 2007 will combine
extrapolated solar wind data with measurements from a wide range of
locations within the Saturn magnetosphere by Cassini. In the course of
making these observations, it will be possible to fully map the auroral
footprints of Io and the other satellites to determine both the local
magnetic field geometry and the controlling factors in the electromagnetic
interaction of each satellite with the corotating magnetic field and plasma
density. Also in the course of making these observations, the auroral
emission properties will be compared with the properties of the near-IR
ionospheric emissions {from ground-based observations} and non thermal radio
emissions, from ground-based observations for Jupiter?s decametric radiation
and Cassini plasma wave measurements of the Saturn Kilometric Radiation
{SKR}.

WFPC2 10832

Solving the microlensing puzzle: An HST high-resolution imaging approach

We propose to use the HST Advanced Camera for Surveys High Resolution
Channel to obtain high resolution imaging data for 10 bona-fide LMC
microlensing events seen in the original MACHO survey. The purpose of this
survey will be to assess whether or not the lens and source stars have
separated enough to be resolved since the original microlensing event took
place - about a decade has passed since the original MACHO survey and the
HST WFPC2 follow-up observations of the microlensing events. If the
components of the lensing event are resolved, we will determine the apparent
magnitude and color of both the lens and the source stars. These data, in
combination with Spitzer/IRAC data and Magellan near-IR JHK data, will be
used to ascertain the basic properties of the lens stars. With the majority
of the microlensing events in the original MACHO survey observed at the
highest spatial resolution currently possible, we will be able to draw
important conclusions as to what fraction of these events have lenses which
belong to some population of dwarf stars in the disk and what fraction must
be due to lenses in the halo or beyond. These data will greatly increase our
understanding of the structure of the Galaxy by characterizing the stellar
population responsible for the gravitational microlensing.

WFPC2 10800

Kuiper Belt Binaries: Probes of Early Solar System Evolution

Binaries in the Kuiper Belt are a scientific windfall: in them we have
relatively fragile test particles which can be used as tracers of the early
dynamical evolution of the outer Solar System. We propose to continue a
Snapshot program using the ACS/HRC that has a demonstrated discovery
potential an order of magnitude higher than the HST observations that have
already discovered the majority of known transneptunian binaries. With this
continuation we seek to reach the original goals of this project: to
accumulate a sufficiently large sample in each of the distinct populations
collected in the Kuiper Belt to be able to measure, with statistical
significance, how the fraction of binaries varies as a function of their
particular dynamical paths into the Kuiper Belt. Today's Kuiper Belt bears
the imprints of the final stages of giant-planet building and migration;
binaries may offer some of the best preserved evidence of that long-ago era.

WFPC2 10786

Rotational state and composition of Pluto's outer satellites

We propose an intricate set of observations aimed at discovering the
rotational state of the newly discovered satellites of Pluto, S/2005 P1 and
S/2005 P2. These observations will indicate if the satellites are in
synchronous rotation or not. If they are not, then the observations will
determine the rotational period or provide tight constraints on the
amplitude. The other primary goal is to extend the wavelength coverage of
the colors of the surface and allow us to constrain the surface compositions
of both objects. From these data we will also be able to significantly
improve the orbits of P1 and P2, improve the measurement of the bulk density
of Charon, and search for albedo changes on the surface of Pluto.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10817 - GSacq(2,3,2) failed due to search radius limit exceeded

During LOS GSacq(2,3,2) scheduled at 140/04:31:31 failed due to search
radius limit exceeded on FGS 2. ESB a05 (exceeded search radius limit) was
received. OBAD2 at 04:26:31 showed errors of V1= 38.65, V2=28.45, V3=40.61,
RSS=62.87.

During LOS the REacq(2,3,2) scheduled at 140/06:10:02 also failed due to
search radius limit exceeded on FGS 2.

10818 - GSAcq (1,2,2) failed to RGA Hold (Gyro Control)

At 140/18:15:30 GSAcq (1,2,2) scheduled from 18:12:08-18:19:32 had failed to
RGA Hold (Gyro Control) due to mnemonic QSTOP on FGS 1. At 18:04:26 received
one 486 STB message 1805 "FHST Moving Target Detected".

OBAD #1 RSS: 3054.12
OBAD #2 RSS: 14.96
OBAD MAP: not scheduled

10819 - ACS 779 Fold Mechanism Move was Blocked

At 140/18:20:24 "Fold Mechanism Move Was Blocked P=0, T=38393. This was the
result of the failed GSAcq at 18:12:08 so the TDF was down when the fold
mechanism move to the SBC position was commanded. The move is blocked and
SBC MAMA HV will remain on. The MAMA HV staying on is a new feature for ACS
FSW CS4.01.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL

FGS GSacq 24 22
FGS REacq 13 12
OBAD with Maneuver 74 74

SIGNIFICANT EVENTS: (None)