Daily Report #4413

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 # 4413

PERIOD COVERED: UT July 26, 2007 (DOY 207)

OBSERVATIONS SCHEDULED

WFPC2 10583

Resolving the LMC Microlensing Puzzle: Where Are the Lensing Objects ?

We are requesting 32 HST orbits to help ascertain the nature of the
population that gives rise to the observed set of microlensing events
towards the LMC. The SuperMACHO project is an ongoing ground-based
survey on the CTIO 4m that has demonstrated the ability to detect LMC
microlensing events in real-time via frame subtraction. The
improvement in angular resolution and photometric accuracy available
from HST will allow us to 1} confirm that the detected flux excursions
arise from LMC source stars rather than extended objects {such as for
background supernovae or AGN}, and 2} obtain reliable baseline flux
measurements for the objects in their unlensed state. The latter
measurement is important to resolve degeneracies between the event
timescale and baseline flux, which will yield a tighter constraint on
the microlensing optical depth.

S/C 4974

TRTTEST

The Transient Response Test is for the periodic performance
monitoring
of the FGS 2R servo A mechanism.

WFPC2 10900

Optical polarimetry of PSR B0540-69 and its synchrotron nebula.

Polarization measurements of pulsars and of their synchrotron nebulae
are uniquely able to provide deep insights into the highly magnetized
relativistic environment of young rotating neutron stars. Apart from
the radio band, pulsar polarization is best measured in the optical,
for the rare cases of detectable optical emission. One of the
brightest pulsars together with Crab {PSR B0531+21} and Vela {PSR
B0833-45}, for which optical polarization measurements support the
newly developed two-pole caustic model {TPC}, is PSR B0540-69 in the
Large Magellanic Clouds, often referred as the Crab Twin for their
overall similarities in both age and energetics. Together with the
Crab, PSR B0540-69 is also the only pulsar embedded in a synchrotron
nebula visible at optical wavelengths. We plan to observe PSR B0540-69
and its compact nebula {4 arcsec diameter} with the Advanced Camera
for Surveys {ACS} and the Wide Field Channel {WFC} detector using UV
and visual polarization filters. Thanks to the superb angular
resolution of ACS, these observations will allow us to spectacularly
resolve the pulsar from its nebular background, providing the first
firm measure of the pulsar polarization which will be crucial to
assess, on a broader sample, the validity of the TPC model with
respect to other pulsars magnetosphere models. These observations will
also provide the first detailed polarization map of the nebula,
including the jet and the torus seen in our previous WFPC2 images.

WFPC2 11079

Treasury Imaging of Star Forming Regions in the Local Group:
Complementing the GALEX and NOAO Surveys

We propose to use WFPC2 to image the most interesting star-forming
regions in the Local Group galaxies, to resolve their young stellar
populations. We will use a set of filters including F170W, which is
critical to detect and characterize the most massive stars, to whose
hot temperatures colors at longer wavelengths are not sensitive.
WFPC2's field of view ideally matches the typical size of the
star-forming regions, and its spatial resolution allows us to measure
individual stars, given the proximity of these galaxies. The resulting
H-R diagrams will enable studies of star- formation properties in
these regions, which cover largely differing metallicities {a factor
of 17, compared to the factor of 4 explored so far} and
characteristics. The results will further our understanding of the
star-formation process, of the interplay between massive stars and
environment, the properties of dust, and will provide the key to
interpret integrated measurements of star-formation indicators {UV,
IR, Halpha} available for several hundreds more distant galaxies. Our
recent deep surveys of these galaxies with GALEX {FUV, NUV} and
ground-based imaging {UBVRI, Halpha, [OIII] and [SII]} provided the
identification of the most relevant SF sites. In addition to our
scientific analysis, we will provide catalogs of HST photometry in 6
bands, matched corollary ground-based data, and UV, Halpha and IR
integrated measurements of the associations, for comparison of
integrated star-formation indices to the resolved populations. We
envisage an EPO component.

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:

#18116-0* TRT Test #15 @ 207/1625z
#18054-0* Preview KF Sun Vector Data via Telemetry Diags (Generic) @
207/1626z

COMPLETED OPS NOTES: (None)

*********************** SCHEDULED***** SUCCESSFUL
FGS GSacq***************** 9************* 9
FGS REacq***************** 3************* 3
OBAD with Maneuver* 28************ 28

SIGNIFICANT EVENTS:

The FGS-2R TRT test #15 was successfully completed today at
207/16:26z. Analysis and results will be presented at the next GSAWG
meeting.