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       # 4326

PERIOD COVERED: UT March 23,24,25, 2007 (DOY 082,083,084)

OBSERVATIONS SCHEDULED

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration - CR Persistence Part 6

A new proceedure proposed to alleviate the CR-persistence problem of

NICMOS. Dark frames will be obtained immediately upon exiting the SAA

contour 23, and everytime 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 i

mages. Each observation will need its own CRMAP, as different SAA

passages leave different imprints on the NICMOS detectors.

WFPC2 11096

Hubble Heritage imaging of Jupiter during the New Horizons encounter HST

Proposal 11096

WFPC2 images of Jupiter in Feb 2007 in support of New Horizons flyby of

Jupiter. This Hubble Heritage DD program is working in concert with the

existing GO programs by John Clarke {10862} and John Spencer {10871}.

NIC3 11080

Exploring the Scaling Laws of Star Formation

As a variety of surveys of the local and distant Universe are

approaching a full census of galaxy populations, our attention needs to

turn towards understanding and quantifying the physical mechanisms that

trigger and regulate the large-scale star formation rates {SFRs} in

galaxies.

FGS 10989

Astrometric Masses of Extrasolar Planets and Brown Dwarfs

We propose observations with HST/FGS to estimate the astrometric

elements {perturbation orbit semi-major axis and inclination} of

extra-solar planets orbiting six stars. These companions were originally

detected by radial velocity techniques. We have demonstrated that FGS

astrometry of even a short segment of reflex motion, when combined with

extensive radial velocity information, can yield useful inclination

information {McArthur et al. 2004}, allowing us to determine companion

masses. Extrasolar planet masses assist in two ongoing research

frontiers. First, they provide useful boundary conditions for models of

planetary formation and evolution of planetary systems. Second, knowing

that a star in fact has a plantary mass companion, increases the value

of that system to future extrasolar planet observation missions such as

SIM PlanetQuest, TPF, and GAIA.

FGS 10912

Trigonometric Calibration of the Distance Scale for Classical Novae

The distance scale for classical novae is important for understanding

the stellar physics of their thermonuclear runaways, their contribution

to Galactic nucleosynthesis, and their use as extragalactic standard

candles. Although it is known that there is a relationship between their

absolute magnitudes at maximum light and their subsequent rates of

decline--the well-known maximum-magnitude rate-of-decline {MMRD}

relation--it is difficult to set the zero-point for the MMRD because of

the very uncertain distances of Galactic novae. We propose to measure

precise trigonometric parallaxes for the quiescent remnants of the four

nearest classical novae. We will use the Fine Guidance Sensors, which

are proven to be capable of measuring parallaxes with errors of ~0.2

mas, well below what is possible from the ground.

WFPC2 10910

HST / Chandra Monitoring of a Dramatic Flare in the M87 Jet

As the nearest galaxy with an optical jet, M87 affords an unparalleled

opportunity to study extragalactic jet phenomena at the highest

resolution. During 2002, HST and Chandra monitoring of the M87 jet

detected a dramatic flare in knot HST-1 located ~1" from the nucleus.

Its optical brightness eventually increased seventy-fold and peaked in

2005; the X- rays show a similarly dramatic outburst. In both bands

HST-1 is still extremely bright and greatly outshines the galaxy

nucleus. To our knowledge this is the first incidence of an optical or

X-ray outburst from a jet region which is spatially distinct from the

core source -- this presents an unprecedented opportunity to study the

processes responsible for non- thermal variability and the X-ray

emission. We propose five epochs of HST/ACS flux monitoring during Cycle

15, as well as seven epochs of Chandra/ACIS observation {5ksec each,

five Chandra epochs contemporary with HST}. At two of the HST/ACS epochs

we also gather spectral information and map the magnetic field

structure. The results of this investigation are of key importance not

only for understanding the nature of the X-ray emission of the M87 jet,

but also for understanding flares in blazar jets, which are highly

variable, but where we have never before been able to resolve the

flaring region in the optical or X-rays. These observations will allow

us to test synchrotron emission models for the X- ray outburst,

constrain particle acceleration and loss timescales, and study the jet

dynamics associated with this flaring component.

WFPC2 10886

The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

As a continuation of the highly successful Sloan Lens ACS {SLACS} Survey

for new strong gravitational lenses, we propose one orbit of ACS-WFC

F814W imaging for each of 50 high-probability strong galaxy-galaxy lens

candidates. These observations will confirm new lens systems and permit

immediate and accurate photometry, shape measurement, and mass modeling

of the lens galaxies. The lenses delivered by the SLACS Survey all show

extended source structure, furnishing more constraints on the projected

lens potential than lensed-quasar image positions. In addition, SLACS

lenses have lens galaxies that are much brighter than their lensed

sources, facilitating detailed photometric and dynamical observation of

the former. When confirmed lenses from this proposal are combined with

lenses discovered by SLACS in Cycles 13 and 14, we expect the final

SLACS lens sample to number 80--100: an approximate doubling of the

number of known galaxy-scale strong gravitational lenses and an

order-of-magnitude increase in the number of optical Einstein rings. By

virtue of its homogeneous selection and sheer size, the SLACS sample

will allow an unprecedented exploration of the mass structure of the

early-type galaxy population as a function of all other observable

quantities. This new sample will be a valuable resource to the

astronomical community by enabling qualitatively new strong lensing

science, and as such we will waive all but a short {3-month} proprietary

period on the observations.

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.

NIC2 10849

Imaging Scattered Light from Debris Disks Discovered by the Spitzer

Space Telescope around 21 Sun-like Stars

We propose to use the high-contrast capability of the NICMOS coronagraph

to image a sample of newly discovered circumstellar disks associated

with Sun-like stars. These systems were identified by their strong

thermal infrared {IR} emission with the Spitzer Space Telescope as part

of the Spitzer Legacy Science program titled "The Formation and

Evolution of Planetary Systems" {FEPS, P.I.: M.Meyer}. Modeling of the

thermal excess emission from the spectral energy distributions alone

cannot distinguish between narrowly confined high-opacity disks and

broadly distributed, low-opacity disks. By resolving light scattered by

the circumstellar material, our proposed NICMOS observations can break

this degeneracy, thus revealing the conditions under which planet

formation processes are occuring or have occured. For three of our

IR-excess stars that have known radial-velocity planets, resolved

imaging of the circumstellar debris disks may further offer an

unprecedented view of planet-disk interactions in an extrasolar

planetary system. Even non-detections of the light scattered by the

circumstellar material will place strong constraints on the disk

geometries, ruling out disk models with high optical depth. Unlike

previous disk imaging programs, our program contains a well-defined

sample of ~1 solar mass stars covering a range of ages from 3 Myr to 3

Gyr, thus allowing us to study the evolution of disks from primordial to

debris for the first time. The results from our program will greatly

improve our understanding of the architecture of debris disks around

Sun-like stars, and will create a morphological context for the

existence of our own solar system. This proposal is for a continuation

of an approved Cycle 14 program {GO/10527, P.I.: D. Hines}.

ACS/SBC 10815

The Blue Hook Populations of Massive Globular Clusters

Blue hook stars are a class of hot {~35,000 K} subluminous horizontal

branch stars that have been recently discovered using HST ultraviolet

images of the globular clusters omega Cen and NGC 2808. These stars

occupy a region of the HR diagram that is unexplained by canonical

stellar evolution theory. Using new theoretical evolutionary and

atmospheric models, we have shown that the blue hook stars are very

likely the progeny of stars that undergo extensive internal mixing

during a late helium core flash on the white dwarf cooling curve. This

"flash mixing" produces an enormous enhancement of the surface helium

and carbon abundances, which suppresses the flux in the far ultraviolet.

Although flash mixing is more likely to occur in stars that are born

with high helium abundances, a high helium abundance, by itself, does

not explain the presence of a blue hook population - flash mixing of the

envelope is required. We propose ACS ultraviolet {SBC/F150LP and

HRC/F250W} observations of the five additional globular clusters for

which the presence of blue hook stars is suspected from longer

wavelength observations. Like omega Cen and NGC 2808, these five targets

are also among the most massive globular clusters, because less massive

clusters show no evidence for blue hook stars. Because our targets span

1.5 dex in metallicity, we will be able to test our prediction that

flash-mixing should be less drastic in metal-rich blue hook stars. In

addition, our observations will test the hypothesis that blue hook stars

only form in globular clusters massive enough to retain the helium-

enriched ejecta from the first stellar generation. If this hypothesis is

correct, then our observations will yield important constraints on the

chemical evolution and early formation history in globular clusters, as

well as the role of helium self-enrichment in producing blue horizontal

branch morphologies and multiple main sequence turnoffs. Finally, our

observations will provide new insight into the formation of the hottest

horizontal branch stars, with implications for the origin of the hot

helium-rich subdwarfs in the Galactic field.

ACS/SBC 10810

The Gas Dissipation Timescale: Constraining Models of Planet Formation

We propose to constrain planet-formation models by searching for

molecular hydrogen emission around young {10-50 Myr} solar-type stars

that have evidence for evolved dust disks. Planet formation models show

that the presence of gas in disks is crucial to the formation of BOTH

giant and terrestrial planets, influences dust dynamics, and through

tidal interactions with giant planets leads to orbital migration.

However, there is a lack of systematic information on the presence and

lifetime of gas residing at planet-forming radii. We will use a newly

identified broad continuum emission feature of molecular hydrogen at

1600 Angstrom to search for residual gas within an orbital radius of

5-10 AU around young stars that have evolved beyond the optically thick

T Tauri phase. These observations will enable the most sensitive probe

to date of remant gas in circumstellar disks, detecting surfaces

densites of ~0.0001 g/cm^2, or less than 10^-5 of the theoretical

"mininum mass" solar nebula from which our solar system is thought to

have formed. Our observations are designed to be synergistic with

ongoing searches for gas emission that is being performed using the

Spitzer Space Telescope in that the proposed HST observations are ~100

times more sensitive and will have 50 times higher angular resolution.

These combined studies will provide the most comprehensive view of

residual gas in proto-planetary disks and can set important constraints

on models of planet formation.

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: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                      SCHEDULED      SUCCESSFUL

FGS GSacq               32                 32                       

FGS REacq               09                 09              

OBAD with Maneuver 82                 82                                  

SIGNIFICANT EVENTS: (None)