Notice: Due to the conversion of some ACS WFC or HRC observations into

WFPC2, or NICMOS observations after the loss of ACS CCD science

capability in January, there may be an occasional discrepancy between a

proposal's listed (and correct) instrument usage and the abstract that

follows it.

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      # 4418

PERIOD COVERED: UT August 2, 2007 (DOY 214)

OBSERVATIONS SCHEDULED

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

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.

NIC2 10854

Coronagraphic Imaging of Bright New Spitzer Debris Disks II.

Fifteen percent of bright main sequence stars possess dusty

circumstellar debris disks revealed by far-infrared photometry. These

disks are signposts of planetary systems: collisions among larger,

unseen parent bodies maintain the observed dust population against

losses to radiation pressure and P-R drag. Images of debris disks at

optical, infrared, and millimeter wavelengths have shown central holes,

rings, radial gaps, warps, and azimuthal asymmetries which indicate the

presence of planetary mass perturbers. Such images provide unique

insights into the structure and dynamics of exoplanetary systems.

Relatively few debris disks have been spatially resolved. Only thirteen

have ever been resolved at any wavelength, and at wavelengths < 10

microns {where subarcsec resolution is available}, only ten. Imaging of

many other debris disk targets has been attempted with various HST

cameras/coronagraphs and adaptive optics, but without success. The key

property which renders a debris disk observable in scattered light is

its dust optical depth. The ten disks imaged so far all have a dust

excess luminosity >~ 0.01% that of the central star; no disks with

smaller optical depths have been detected. Most main sequence stars

known to meet this requirement have already been observed, so future

progress in debris disk imaging depends on discovering additional stars

with large infrared excess. The Spitzer Space Telescope offers the best

opportunity in 20 years to identify new examples of high optical depth

debris disk systems. We propose to complete ACS coronagraphic imaging

followup of bright, new debris disks discovered during the first two

years of the Spitzer mission, by observing three additional targets in

Cycle 15. Our goal is to obtain the first resolved images of these disks

at ~3 AU resolution, define the disk sizes and orientations,and uncover

disk substructures indicative of planetary perturbations. The results

will open wider a window into the structure of planetary systems.

WFPC2 11029

WFPC2 CYCLE 15 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 15 decon proposal xxxx 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.

WFPC2 11084

Probing the Least Luminous Galaxies in the Local Universe

We propose to obtain deep color-magnitude data of eight new Local Group

galaxies which we recently discovered: Andromeda XI, Andromeda XII, and

Andromeda XIII {satellites of M31}; Canes Venatici I, Canes Venatici II,

Hercules, and Leo IV {satellites of the Milky Way}; and Leo T, a new

"free-floating" Local Group dwarf spheroidal with evidence for recent

star formation and associated H I gas. These represent the least

luminous galaxies known at *any* redshift, and are the only accessible

laboratories for studying this extreme regime of galaxy formation. With

deep WFPC-2 F606W and F814W pointings at their centers, we will

determine whether these objects contain single or multiple age stellar

populations, as well as whether these objects display a range of

metallicities.

WFPC2 11169

Collisions in the Kuiper belt

For most of the 15 year history of observations of Kuiper belt objects,

it has been speculated that impacts must have played a major role in

shaping the physical and chemical characteristics of these objects, yet

little direct evidence of the effects of such impacts has been seen. The

past 18 months, however, have seen an explosion of major new discoveries

giving some of the first insights into the influence of this critical

process. From a diversity of observations we have been led to the

hypotheses that: {1} satellite-forming impacts must have been common in

the Kuiper belt; {2} such impacts led to significant chemical

modification; and {3} the outcomes of these impacts are sufficiently

predictable that we can now find and study these impact-derived systems

by the chemical and physical attributes of both the satellites and the

primaries. If our picture is correct, we now have in hand for the first

time a set of incredibly powerful tools to study the frequency and

outcome of collisions in the outer solar system. Here we propose three

linked projects that would answer questions critical to the multiple

prongs of our hypothesis. In these projects we will study the chemical

effects of collisions through spectrophotometric observations of

collisionally formed satellites and through the search for additional

satellites around primaries with potential impact signatures, and we

will study the physical effects of impacts through the examination of

tidal evolution in proposed impact systems. The intensive HST program

that we propose here will allow us to fully test our new hypotheses and

will provide the ability to obtain the first extensive insights into

outer solar system impact processes.

WFPC2/NIC3 11188

First Resolved Imaging of Escaping Lyman Continuum

The emission from star-forming galaxies appears to be responsible for

reionization of the universe at z>6. However, the models that attempt to

describe the detailed impact of high- redshift galaxies on the

surrounding inter-galactic medium {IGM} are strongly dependent upon

several uncertain parameters. Perhaps the most uncertain is the fraction

of HI-ionizing photons produced by young stars which escape into the

IGM. Most attempts to measure this "escape fraction" {f_esc} have

produced null results. Recently, a small subset of z~3 Lyman Break

Galaxies {LBGs} has been found exhibiting large escape fractions. It

remains unclear however, what differentiates them from other LBGs.

Several models attempt to explain how such a large fraction of ionizing

continuum can escape through the HI and dust in the ISM {eg. "chimneys"

created by SNe winds, globular cluster formation, etc.}, each producing

unique signatures which can be observed with resolved imaging of the

escaping Lyman continuum. We propose a deep, high resolution WFPC2 image

of the ionizing continuum {F336W} and the rest-frame 1500 Angstrom

continuum {F606W} of five of the six known LBGs with large escape

fractions. These LBGs all fit within a single WFPC2 pointing, yielding

high observing efficiency. Additionally, they all have z~3.1 or higher,

the optimal redshift range for probing the Lyman Continuum region with

available WFPC2 filters. These factors make our proposed sample

especially suitable for follow- up. With these data we will discern the

mechanisms responsible for producing large escape fractions, and

therefore gain insight into the process of reionization.

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               06                 06              

OBAD with Maneuver 26                 26              

SIGNIFICANT EVENTS: (None)