HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      # 4584

PERIOD COVERED: UT April 07, 2008 (DOY 098)

OBSERVATIONS SCHEDULED

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration - CR Persistence Part 6

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 i

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

passages leave different imprints on the NICMOS detectors.

NIC2 11155

Dust Grain Evolution in Herbig Ae Stars: NICMOS Coronagraphic Imaging

and Polarimetry

We propose to take advantage of the sensitive coronagraphic capabilities

of NICMOS to obtain multiwavelength coronagraphic imaging and

polarimetry of primordial dust disks around young intermediate-mass

stars {Herbig Ae stars}, in order to advance our understanding of how

dust grains are assembled into larger bodies. Because the polarization

of scattered light is strongly dependent on scattering particle size and

composition, coronagraphic imaging polarimetry with NICMOS provides a

uniquely powerful tool for measuring grain properties in spatially

resolved circumstellar disks. It is widely believed that planets form

via the gradual accretion of planetesimals in gas-rich, dusty

circumstellar disks, but the connection between this suspected process

and the circumstellar disks that we can now observe around other stars

remains very uncertain. Our proposed observations, together with

powerful 3-D radiative transfer codes, will enable us to quantitatively

determine dust grain properties as a function of location within disks,

and thus to test whether dust grains around young stars are in fact

growing in size during the putative planet-formation epoch. HST imaging

polarimetry of Herbig Ae stars will complement and extend existing

polarimetric studies of disks around lower-mass T Tauri stars and debris

disks around older main-sequence stars. When combined with these

previous studies, the proposed research will help us establish the

influence of stellar mass on the growth of dust grains into larger

planetesimals, and ultimately to planets. Our results will also let us

calibrate models of the thermal emission from these disks, a critical

need for validating the properties of more distant disks inferred on the

basis of spectral information alone.

NIC2 11157

NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the

Stellar Mass Spectrum

Association of planetary systems with dusty debris disks is now quite

secure, and advances in our understanding of planet formation and

evolution can be achieved by the identification and characterization of

an ensemble of debris disks orbiting a range of central stars with

different masses and ages. Imaging debris disks in starlight scattered

by dust grains remains technically challenging so that only about a

dozen systems have thus far been imaged. A further advance in this field

needs an increased number of imaged debris disks. However, the technical

challenge of such observations, even with the superb combination of HST

and NICMOS, requires the best targets. Recent HST imaging investigations

of debris disks were sample-limited not limited by the technology used.

We performed a search for debris disks from a IRAS/Hipparcos cross

correlation which involved an exhaustive background contamination check

to weed out false excess stars. Out of ~140 identified debris disks, we

selected 22 best targets in terms of dust optical depth and disk angular

size. Our target sample represents the best currently available target

set in terms of both disk brightness and resolvability. For example, our

targets have higher dust optical depth, in general, than newly

identified Spitzer disks. Also, our targets cover a wider range of

central star ages and masses than previous debris disk surveys. This

will help us to investigate planetary system formation and evolution

across the stellar mass spectrum. The technical feasibility of this

program in two-gyro mode guiding has been proven with on-orbit

calibration and science observations during HST cycles 13, 14, and 15.

NIC3 11120

A Paschen-Alpha Study of Massive Stars and the ISM in the Galactic

Center

The Galactic center (GC) is a unique site for a detailed study of a

multitude of complex astrophysical phenomena, which may be common to

nuclear regions of many galaxies. Observable at resolutions

unapproachable in other galaxies, the GC provides an unparalleled

opportunity to improve our understanding of the interrelationships of

massive stars, young stellar clusters, warm and hot ionized gases,

molecular clouds, large scale magnetic fields, and black holes. We

propose the first large-scale hydrogen Paschen alpha line survey of the

GC using NICMOS on the Hubble Space Telescope. This survey will lead to

a high resolution and high sensitivity map of the Paschen alpha line

emission in addition to a map of foreground extinction, made by

comparing Paschen alpha to radio emission. This survey of the inner 75

pc of the Galaxy will provide an unprecedented and complete search for

sites of massive star formation. In particular, we will be able to (1)

uncover the distribution of young massive stars in this region, (2)

locate the surfaces of adjacent molecular clouds, (3) determine

important physical parameters of the ionized gas, (4) identify compact

and ultra-compact HII regions throughout the GC. When combined with

existing Chandra and Spitzer surveys as well as a wealth of other

multi-wavelength observations, the results will allow us to address such

questions as where and how massive stars form, how stellar clusters are

disrupted, how massive stars shape and heat the surrounding medium, and

how various phases of this medium are interspersed.

WFPC2 11017

Hubble Heritage Observations of SN1006

The Hubble Heritage team will obtain broadband images of SN1006 to

combine with the Halpha data obtained in proposal 10577 (PI: Raymond).

Three broadband filters will be used with two pointings of the WFPC2 to

obtain star colors. A composite image of the Heritage stars along with

the Halpha filament will be created, resulting in a public release

image.

WFPC2 11070

WFPC2 CYCLE 15 Standard Darks - part II

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 11176

Location and the Origin of Short Gamma-Ray Bursts

During the past decade extraordinary progress has been made in

determining the origin of long- duration gamma-ray bursts. It has been

conclusively shown that these objects derive from the deaths of massive

stars. Nonetheless, the origin of their observational cousins,

short-duration gamma-ray bursts {SGRBs} remains a mystery. While SGRBs

are widely thought to result from the inspiral of compact binaries, this

is a conjecture. A number of hosts of SGRBs have been identified, and

have been used by some to argue that SGRBs derive primarily from an

ancient population {~ 5 Gyr}; however, it is not known whether this

conclusion more accurately reflects selection biases or astrophysics.

Here we propose to employ a variant of a technique that we pioneered and

used to great effect in elucidating the origins of long-duration bursts.

We will examine the degree to which SGRB locations trace the red or blue

light of their hosts, and thus old or young stellar populations. This

approach will allow us to study the demographics of the SGRB population

in a manner largely free of the distance dependent selection effects

which have so far bedeviled this field, and should give direct insight

into the age of the SGRB progenitor population.

WFPC2 11513

The afterglow and host galaxy of GRB 080319: the first "naked eye" burst

The optical flash from GRB 080319 reached a magnitude of about 5.5

within a few seconds of the start of the burst, making it the first

"naked eye" GRB. It's redshift has been determined as z=0.94 (about 7

billion light years distance) and hence it is by far the most distant

naked eye source known.

HST has a key role to play in helping study this event, by providing the

late time monitoring of the light curve and colour of the afterglow.

This will allow us to constrain any breaks which may indicate a

collimated outflow, to search for an underlying supernova component and

to reveal the nature of the host galaxy, and the location of the burst

within it.

Not surprisingly this object is attracting considerable attention both

in the professional astrophysical community and also in the general

public. We believe that HST observations of this GRB would be welcomed

by both of these communities.

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               10                 10                  

FGS REacq               03                 03                  

OBAD with Maneuver 26                 26                 

SIGNIFICANT EVENTS: (None)