Daily #4090

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4090

PERIOD COVERED: UT April 11, 2006 (DOY 101)

OBSERVATIONS SCHEDULED

ACS/HRC 10512

Search for Binaries Among Faint Jupiter Trojan Asteroids

We propose an ambitious SNAPSHOT program to survey faint Jupiter
Trojan asteroids for binary companions. We target 150 objects, with
the expectation of acquiring data on about 50%. These objects span
Vmag = 17.5-19.5, a range inaccessible with ground-based adaptive
optics. We now have a significant sample from our survey of brighter
Trojans to suggest that the binary fraction is similar to that which
we find among brighter main-belt asteroids, roughly 2%. However, our
observations suggest a higher binary fraction for smaller main-belt
asteroids, probably the result of a different formation mechanism
{evident also from the physical characteristics of the binaries}.
Because the collision environment among the Trojans is similar to that
of the Main Belt, while the composition is likely to be very
different, sampling the binary fraction among the fainter Trojans
should help us understand the collisional and binary formation
mechanisms at work in various populations, including the Kuiper Belt,
and help us evaluate theories for the origin of the Trojans.
Calibration of and constraints on models of binary production and
collisional evolution can only be done using these large-scale,
real-life physical systems that we are beginning now to find and
utilize.

ACS/HRC 10559

Astrometric monitoring of binary L and T dwarfs

We propose to obtain high angular resolution ACS images of five binary
L and T dwarfs in order to determine their orbital parameters and
dynamical masses, and directly constrain the evolutionary models of
ultracool and substellar objects. The binaries have estimated periods
ranging between 5 and 14 years. All of them have already been resolved
at least twice {sometimes more} using HST, providing first and second
epochs measurements. We propose to obtain two more ACS imaging
observations separated by 9 to 12 months during cycle 14. The expected
period coverage should therefore range between 35% and 117%, allowing
us to compute precise orbital parameters and masses. Our sample is
large enough and covers a sufficiently wide range of spectral types
{from L3 to T5.5} to allow us to obtain strong constraints the
evolutionnary models.

ACS/HRC 10625

A Multiwavelength Investigation of Comet 73P/SW3-C

The nucleus of comet 73P/Schwassmann--Wachmann~3 experienced a
non-tidal breakup in late 1995. The largest fragment {73P/SW3-C}
survived its subsequent perihelion passage in 2001 and will return in
2006, when it will pass very close to {0.08 AU} Earth. This represents
an outstanding opportunity to characterize a fresh cometary nucleus,
and we propose an intensive investigation using both the Hubble and
Spitzer telescopes. Employing the technique that our group has
developed over the past decade to characterize 31 cometary nuclei, we
will use HST/ACS to photometrically resolve the nucleus of 73P/SW3-C
at optical wavelengths and SST/MIPS to do the same thing at thermal
infrared wavelengths, thereby allowing us to determine both the size
and albedo of this fragment. We also plan to measure the lightcurve of
73P/SW3-C to obtain detailed shape information, and use HST/NICMOS to
probe the composition, in particular to search for evidence of icy
material on the fresh surface. Previous observations indicate that
most of the remaining mass of 73P/SW3 is in the form of numerous small
fragments. A few of those may have been captured by the C fragment,
and the determination of their orbits would allow the first, direct
measurement of the mass of a cometary nucleus. Thus, we will also
perform a deep search for any possible companions to the C-fragment.

ACS/HRC 10738

Earth Flats

Sky flats will be obtained by observing the bright Earth with the HRC
and WFC. These observations will be used to verify the accuracy of the
flats currently in the pipeline and to monitor any changes. Weekly
coronagraphic monitoring is required to assess the changing position
of the spots.

ACS/HRC/WFC 10514

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 a
Snapshot program using the ACS/HRC that has a potential discovery
efficiency an order of magnitude higher than the HST observations that
have already discovered the majority of known transneptunian binaries.
By more than doubling the number of observed objects in dynamically
hot and cold subpopulations we will be able to answer, with
statistical significance, the question of whether these groups differ
in the abundance of binaries as a result 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.

ACS/WFC 10433

The Cepheid PL-Z

We are proposing to empirically calibrate the metallicity sensitivity
of the Cepheid Period- Luminosity relation at the highest metallicity
range so far observed in nearby galaxies. To do this we will obtain
the I-band Population II Tip of the Red Giant Branch {TRGB} distances
to two galaxies, NGC 3627 and NGC 3368, both of which have comparable
{Cepheid} distances of 11 Mpc and have almost identical {very high}
metallicities of 12 + log[O/H] = +9.3. At present, observers have
extremely divergent views on the magnitude of the metallicity effect
on the Cepheid zero point, and theorists cannot even agee upon the
sign of the effect.

ACS/WFC 10732

ACS internal CTE monitor

The charge transfer efficiency {CTE} of the ACS CCD detectors will
decline as damage due to on-orbit radiation exposure accumulates. This
degradation will be closely monitored at regular intervals, because it
is likely to determine the useful lifetime of the CCDs. All the data
for this program is acquired using internal targets {lamps} only, so
all of the exposures should be taken during Earth occultation time
{but not during SAA passages}. This program emulates the ACS
pre-flight ground calibration and post-launch SMOV testing {program
8948}, so that results from each epoch can be directly compared.
Extended Pixel Edge Response {EPER} and First Pixel Response {FPR}
data will be obtained over a range of signal levels for both the Wide
Field Channel {WFC}, and the High Resolution Channel {HRC}.

ACS/WFC 10775

An ACS Survey of Galactic Globular Clusters

We propose to conduct an ACS/WFC imaging survey of Galactic globular
clusters. We will construct the most extensive and deepest set of
photometry and astrometry to-date for these systems reaching a main
sequence mass of ~0.2 solar mass with S/N = 10. We will combine these
data with archival WFPC2 and STIS images to determine proper motions
for the stars in our fields. The resultant cleaned cluster CMDs will
allow us to study a variety of scientific questions. These include
[but are not limited to] 1} the determination of cluster ages and
distances 2} the construction of main sequence mass functions and the
issue of mass segregation 3} the internal motions and dynamical
evolution of globular clusters, and 4} absolute cluster motions,
orbits, and the Milky Way gravitational potential. We anticipate that
the unique resource provided by the proposed treasury archive will
play a central role in the field of globular cluster studies for
decades, with a stature comparable to that of the Hubble Deep Field
for high redshift studies.

NIC1/NC2/NC3 10723

Cycle 14 NICMOS dark current, shading profile, and read noise
monitoring program

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 14. This proposal is a slightly modified version
of proposal 10380 of cycle 13 and 9993 of cycle12 that we cut down
some exposure time to make the observation fit within 24 orbits.

NIC2 10603

Multiwavelength Imaging of Edge-on Protoplanetary Disks: Quantifying
the Growth of Circumstellar Dust

Young, edge-on circumstellar disks are uniquely valuable laboratories
for the study of planet formation. In these objects, the central star
is occulted from direct view, significant PSF artifacts are absent,
and the disk is clearly seen as a central dust lane flanked by faint
disk reflected light. The detailed morphology of these nebulae and its
variation with wavelength provide crucial information on the disk
internal structure and the properties of its constituent dust grains.
A key observable is the slope defining the wavelength dependence of
the dust scattering opacity, which becomes shallower when grain growth
has taken place; multiwavelength resolved disk images are the key
dataset enabling such measurements. Recent analyses of three different
edge-on disks have revealed a diversity in their dust properties that
is indicative of different degrees of dust grain evolution having
taken place in each system. This characterization of disk grain
growth, when applied comparatively to a larger sample of these
objects, would enable the construction of an evolutionary sequence of
young disks at successive stages on the road to planet formation. In
pursuit of this goal, we have identified a sample of 15 edge-on disks
previously discovered by HST or groundbased telescopes, but for which
high fidelity, high spatial resolution images do not yet exist in both
the optical and near-infrared. We propose broad-band multicolor
imaging with NICMOS of all these targets, and ACS imaging of nine of
these targets In combination with existing data, the proposed images
will form a complete database of high resolution optical/near-IR
images for these 15 disk systems. Scattered light modeling will be
used to derive the disk structure and dust properties, yielding
results that will be of fundamental importance for our understanding
of grain properties during protoplanetary disk evolution.

WFPC2 10745

WFPC2 CYCLE 14 INTERNAL MONITOR

This calibration proposal is the Cycle 14 routine internal monitor for
WFPC2, to be run weekly to monitor the health of the cameras. A
variety of internal exposures are obtained in order to provide a
monitor of the integrity of the CCD camera electronics in both bays
{both gain 7 and gain 15 -- to test stability of gains and bias
levels}, a test for quantum efficiency in the CCDs, and a monitor for
possible buildup of contaminants on the CCD windows. These also
provide raw data for generating annual super-bias reference files for
the calibration pipeline.

WFPC2 10748

WFPC2 CYCLE 14 Standard Darks

This dark calibration program obtains dark frames every week in order
to provide data for the ongoing calibration of the CCD dark current
rate, and to monitor and characterize the evolution of hot pixels.
Over an extended period these data will also provide a monitor of
radiation damage to the CCDs.

WFPC2 10751

WFPC2 CYCLE 14 Intflat Linearity Check and Filter Rotation Anomaly
Monitor

Intflat observations will be taken to provide a linearity check: the
linearity test consists of a series of intflats in F555W, in each gain
and each shutter. A combination of intflats, visflats, and earthflats
will be used to check the repeatability of filter wheel motions.
{Intflat sequences tied to decons, visits 1-18 in prop 10363, have
been moved to the cycle 14 decon proposal 10744 for easier
scheduling.} Note: long-exposure WFPC2 intflats must be scheduled
during ACS anneals to prevent stray light from the WFPC2 lamps from
contaminating long ACS external exposures.

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: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 07 07
FGS REacq 08 08
OBAD with Maneuver 18 18

SIGNIFICANT EVENTS: (None)