Daily Report # 4337

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)