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      # 4337

PERIOD COVERED: UT April 09, 2007 (DOY 099)

OBSERVATIONS SCHEDULED

WFPC2 10468

Jupiter's Upper Stratospheric Hazes Probed with Ganymede

I propose to observe a disappearance of Ganymede behind the dark limb of

Jupiter with five filters of the ACS/HRC camera. Two exposures in each

filter can be taken during such an event. The images will provide the

spectral variation of the altitude of the apparent limb of Jupiter. The

altitude of the apparent limb is dependent on the presence of hazes in

Jupiter's stratosphere. Hazes of vertical optical depths below 0.001

could be detected with these observations, providing an extremely

sensitive probe of high hazes. The observations probe altitudes levels

near the 1-mb pressure level, for which we have very limited data. The

creation of aerosols, their growth, and their transport by winds is

currently a mostly theoretical study. It would significantly benefit

from constraints derived from the proposed observations. ACS/HRC is the

only instrument capable of the required spatial resolution in the

ultraviolet. Furthermore, a favorable geometry of Ganymede's orbit

occurs only once every six years. This proposal achieves unique results

with a minimum of HST time.

ACS/SBC 10872

Lyman Continuum Emission in Galaxies at z=1.2

Lyman continuum photons produced in massive starbursts may have played a

dominant role in the reionization of the Universe. Starbursts are

important contributors to the ionizing metagalactic background at lower

redshifts as well. However, their contribution to the background depends

upon the fraction of ionizing radiation that escapes from the intrinsic

opacity of galaxies below the Lyman limit. Current surveys suggest

escape fractions of a few percent, up to 10%, with very few detections

{as opposed to upper limits} having been reported. No detections have

been reported in the epochs between z=0.1 and z=2. We propose to measure

the fraction of escaping Lyman continuum radiation from 15 luminous

z~1.2 galaxies in the GOODS fields. Using the tremendous sensitivity of

the ACS Solar- blind Channel, we will reach AB=30 mag., allowing us to

detect an escape fraction of 1%. We will correlate the amount of

escaping radiation with the photometric and morphological properties of

the galaxies. A non-detection in all sources would imply that QSOs

provide the overwhelming majority of ionizing radiation at z=1.3, and it

would strongly indicate that the properties of galaxies at higher

redshift have to be significantly different for galaxies to dominate

reionization. The deep FUV images will also be useful for extending the

FUV study of other galaxies in the GOODS fields.

ACS/SBC 10907

Testing the first direct measurement of cataclysmic variable evolution:

the search for a circumbinary disk or a low?mass companion around NN

Serpentis

We obtained high time-resolution photometry using the high speed CCD

camera ULTRACAM between 2002 and 2004, which revealed a gradual

reduction in the orbital period of the pre- cataclysmic variable NN

Serpentis. There are three possible explanations for this period change:

firstly, we may have been successful in obtaining the first and only

direct measurement of the braking rate of a close binary system, in

which case our measured values are approximately 2 orders of magnitude

greater than predicted, and pose serious problems for the theory of

close binary evolution. Secondly, the unusually high braking rate may be

caused by the presence of a circumbinary disk, which would help to

answer two of the outstanding problems with current CV theory - namely

the high mass- transfer rates seen in some CVs, and the fact that the

minimum observed value in the CV period distribution is approximately

15% longer than expected. Finally, our observations could be explained

by a light travel-time effect caused by a third body in orbit around the

binary, which would raise major questions about the evolutionary history

of the system, in particular how a third body has managed to remain in a

stable orbit throughout periods of intense mass-loss in the central

binary. We intend to use IRAC observations to search for a mid-infrared

excess in the spectral energy distribution of NN Ser, which would

confirm the presence of either a disk or a third body. We then propose

to use HST imaging to attempt to resolve a third body, allowing us to

discriminate between the two possibilities. If both methods fail to

reveal any extra system components, we will have ruled out our only

remaining alternatives to a genuinely high angular momentum loss rate in

this system, with profound implications for CV evolution.

WFPC2 10166

ACS and WFPC2 Stellar Photometry in the Kepler Mission Target Field

We will observe three regions at the Galactic Equator {GE} to determine

the number of stars in the magnitude range from 18 to 25 in the target

field of the NASA Kepler mission. This mission will search for

Earth-size planets orbiting other stars. The field is a twelve by twelve

degree square in Cygnus. It abuts the GE. The detection technique is to

search photometrically for planetary transits. Faint eclipsing binaries

that are not spatially resolved from the target star by Kepler may cause

confusion, leading to false positive detections. The HST is uniquely

capable of determining the potential magnitude of the issue in the

region of the GE, where stellar densities are extremely high.

WFPC2 11024

WFPC2 CYCLE 15 INTERNAL MONITOR

This calibration proposal is the Cycle 15 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.

FGS 10612

Binary Stars in Cyg OB2: Relics of Massive Star Formation in a

Super-Star Cluster

We propose to make a high angular resolution SNAP survey of the massive

stars in the nearby, super-star cluster Cyg OB2. We will use FGS1r TRANS

mode observations to search for astrometric companions in the separation

range of 0.01 to 1.00 arcsec and in the magnitude difference range

smaller than 4 magnitudes. The observations will test the idea that the

formation of very massive stars involves mergers and the presence of

nearby companions. Discovery of companions to massive stars in this

relatively nearby complex will provide guidance in the interpretation of

apparently supermassive stars in distant locations. The search for

companions will also be important for verification of fundamental

parameters derived from spectroscopy, adjustments to main sequence

fitting and distance estimations, determining third light contributions

of eclipsing binaries, identifying wide colliding wind binaries,

studying the relationship between orbital and spin angular momentum, and

discovering binaries amenable to future mass determinations. The massive

star environment in Cyg OB2 may be similar to the kinds found in the

earliest epoch of star formation, so that a study of the role of

binaries in Cyg OB2 will help us understand the formation processes of

the first stars in the Universe.

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.

NIC2 10847

Coronagraphic Polarimetry of HST-Resolved Debris Disks

We propose to take full advantage of the recently commissioned

coronagraphic polarimetry modes of ACS and NICMOS to obtain imaging

polarimetry of circumstellar debris disks that were imaged previously by

the HST coronagraphs, but without the polarizers. It is well established

that stars form in gas-rich protostellar disks, and that the planets of

our solar system formed from a circum-solar disk. However, the

connection between the circumstellar disks that we observe around other

stars and the processes of planet formation is still very uncertain.

Mid-IR spectral studies have suggested that disk grains are growing in

the environments of young stellar objects during the putative

planet-formation epoch. Furthermore, structures revealed in well

resolved images of circumstellar disks suggest gravitational influences

on the disks from co-orbital bodies of planetary mass. Unfortunately,

existing imaging data provides only rudimentary information abou the

disk grains and their environments. Our proposed observations, which can

be obtained only with HST, will enable us to quantitatively determine

the sizes of the grains and optical depths as functions of their

location within the disks {i.e., detailed tomography}. Armed with these

well-determine physical and geometrical systemic parameters, we will

develop a set of self- consistent models of disk structures to

investigate possible interactions between unseen planets and the disks

from which they formed. Our results will also calibrate models of the

thermal emission from these disks, that will in turn enable us to infer

the properties of other debris disks that cannot be spatially resolved

with current or planned instruments and telescopes.

NIC3 11082

NICMOS Imaging of GOODS: Probing the Evolution of the Earliest Massive

Galaxies, Galaxies Beyond

Deep near-infrared imaging provides the only avenue towards

understanding a host of astrophysical problems, including: finding

galaxies and AGN at z > 7, the evolution of the most massive galaxies,

the triggering of star formation in dusty galaxies, and revealing

properties of obscured AGN. As such, we propose to observe 60 selected

areas of the GOODS North and South fields with NICMOS Camera 3 in the

F160W band pointed at known massive M > 10^11 M_0 galaxies at z > 2

discovered through deep Spitzer imaging. The depth we will reach {26.5

AB at 5 sigma} in H_160 allows us to study the internal properties of

these galaxies, including their sizes and morphologies, and to

understand how scaling relations such as the Kormendy relationship

evolved. Although NIC3 is out of focus and undersampled, it is currently

our best opportunity to study these galaxies, while also sampling enough

area to perform a general NIR survey 1/3 the size of an ACS GOODS field.

These data will be a significant resource, invaluable for many other

science goals, including discovering high redshift galaxies at z > 7,

the evolution of galaxies onto the Hubble sequence, as well as examining

obscured AGN and dusty star formation at z > 1.5. The GOODS fields are

the natural location for HST to perform a deep NICMOS imaging program,

as extensive data from space and ground based observatories such as

Chandra, GALEX, Spitzer, NOAO, Keck, Subaru, VLT, JCMT, and the VLA are

currently available for these regions. Deep high-resolution

near-infrared observations are the one missing ingredient to this

survey, filling in an important gap to create the deepest, largest, and

most uniform data set for studying the faint and distant universe. The

importance of these images will increase with time as new facilities

come on line, most notably WFC3 and ALMA, and for the planning of future

JWST observations.

WFPC2 11023

WFPC2 CYCLE 15 Standard Darks - part 1

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 11031

CTE Background Dependence Closeout

Measuring the charge transfer efficiency {CTE} of an astronomical CCD

camera is crucial to determining the CCD's photometric fidelity across

the field of view. WFPC2's CTE has degraded steadily over the last 13

years because of continuous exposure to trapped particles in HST's

radiation environment. The fraction of photometric signal lost from

WFPC2's CTI {charge transfer inefficiency} is a function of WFPC2's time

in orbit, the integrated signal in the image, the location of the image

on the CCD, and the background signal. Routine monitoring of WFPC2's CTE

over the last 13 years permits an assessment of all but the last

condition. The dependence of CTE on background signal must be

characterized, however, because a large fraction of WFPC2 images have

been obtained under conditions of significant sky background. This

program aims to assess the end-of-life CTE of WFPC2's CCDs separately as

a function of background signal. Traditional images of an off-center

field in NGC 5139 {Omega Cen} are recorded after preflashing {or before

postflashing} the CCDs with internal lamps to provide average background

signals of 0-160 e-, which span the range of sky backgrounds observed in

~99% of long-exposure narrow- and broad-band WFPC2 images.

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               09                 09                

FGS REacq               05                 05                

OBAD with Maneuver 26                 26                

SIGNIFICANT EVENTS: (None)