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      # 4325

PERIOD COVERED: UT March 22, 2007 (DOY 081)

OBSERVATIONS SCHEDULED

ACS/SBC 10814

The Masses for ultraluminous X-ray sources

Ultraluminous X-ray sources are non-nuclear sources in normal disk

galaxies that are either stellar mass black holes that are

super-Eddington emitters, or 1E3-1E4 Msolar black holes emitting

normally. We can distinguish between these models by obtaining

constraints for the mass of the primary, which can be accomplished

through UV objective prism spectra. This strategy begins with the

optical identification of the secondary and identification of its

spectral type in order to determine its mass and the Roche Lobe radius.

Secondly, we need to determine whether an accretion disk is present and

if its high ionization UV line luminosities point to a stellar mass

black hole or a more massive object. Finally, if the black hole is

1E3-1E4 Msolar, the orbital velocity of the secondary is so large that a

Doppler shift will be detectable, even at the modest resolution of the

prism.

ACS/SBC 10862

Comprehensive Auroral Imaging of Jupiter and Saturn during the

International Heliophysical Year

A comprehensive set of observations of the auroral emissions from

Jupiter and Saturn is proposed for the International Heliophysical Year

in 2007, a unique period of especially concentrated measurements of

space physics phenomena throughout the solar system. We propose to

determine the physical relationship of the various auroral processes at

Jupiter and Saturn with conditions in the solar wind at each planet.

This can be accomplished with campaigns of observations, with a sampling

interval not to exceed one day, covering at least one solar rotation.

The solar wind plasma density approaching Jupiter will be measured by

the New Horizons spacecraft, and a separate campaign near opposition in

May 2007 will determine the effect of large-scale variations in the

interplanetary magnetic field {IMF} on the Jovian aurora by

extrapolation from near-Earth solar wind measurements. A similar Saturn

campaign near opposition in Jan. 2007 will combine extrapolated solar

wind data with measurements from a wide range of locations within the

Saturn magnetosphere by Cassini. In the course of making these

observations, it will be possible to fully map the auroral footprints of

Io and the other satellites to determine both the local magnetic field

geometry and the controlling factors in the electromagnetic interaction

of each satellite with the corotating magnetic field and plasma density.

Also in the course of making these observations, the auroral emission

properties will be compared with the properties of the near-IR

ionospheric emissions {from ground-based observations} and non thermal

radio emissions, from ground-based observations for Jupiter?s decametric

radiation and Cassini plasma wave measurements of the Saturn Kilometric

Radiation {SKR}.

WFPC2 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.

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.

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.

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               06                06                       

FGS REacq               08                08              

OBAD with Maneuver 28               28                                  

SIGNIFICANT EVENTS: (None)