Daily # 4254

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4254

PERIOD COVERED: UT December 06, 2006 (DOY 340)

OBSERVATIONS SCHEDULED

ACS/HRC 10867

SAINTS - Supernova 1987A INTensive Survey

SAINTS is a program to observe SN 1987A, the brightest supernova in
383 years, as it morphs into the youngest supernova remnant at age 19.
HST is a unique tool for spatially-resolved observations of the many
physical components of SN 1987A. A violent encounter is now underway
between the fastest-moving debris and the circumstellar ring: the
collision excites "hotspots" that light up suddenly. The optical,
infrared and X-ray fluxes are rising rapidly and vary significantly on
6-month time scales: regularly-spaced HST, SPITZER, and CHANDRA
observations are needed to understand the physics of these shocked
regions. In Cycle 15, the many separate hotspots may begin to fuse as
the shock fully enters the circumstellar ring. Photons from these
shocks may excite previously invisible gas outside the ring, revealing
the true extent of the mass loss that preceded the explosion of
Sanduleak -69 202. The inner debris of the explosion itself, still
excited by radioactive isotopes produced in the explosion, is now
resolved by ACS and seen to be aspherical, providing direct evidence
on the asymmetry of the explosion. Many questions about SN 1987A
remain unanswered despite our diligent efforts at observation and
analysis since the launch of HST. How did the enigmatic three rings
form? Precisely what took place in the core during the core collapse
and bounce? Is a black hole or a neutron star left behind in the
debris? The rich and deep data set from SAINTS will be a resource for
current use and for future reference to help answer these central
questions of supernova science.

ACS/HRC 10878

An ACS Prism Snapshot Survey for z~2 Lyman Limit Systems

We propose to conduct a spectroscopic survey of Lyman limit absorbers
at redshifts 1.7 z 2.2, using ACS/HRC and the PR200L prism. We
have selected 100 quasars at 2.3 z 2.6 from the Sloan Digital Sky
Survey Spectroscopic Quasar sample, for which no BAL signature is
found at the QSO redshift and no strong metal absorption lines are
present at z 2.3 along the lines of sight. The survey has three main
observational goals. First, we will determine the redshift frequency
dN/dz of the LLS over the column density range 16.3 log N_HI 20.3
cm^-2. Second, we will measure the column density frequency
distribution f{N} for the partial Lyman limit systems {PLLS} over the
column density range 16.3 log N_HI 17.5 cm^-2. Third, we will
identify new sightlines for measurements of the primordial D/H ratio.
With this survey, we will also constrain two key quantities of
cosmological relevance: First, the measurements of dN/dz for optically
thick LLS and f{N} for the PLLS are critical to estimating the
attenuation of extragalactic ionizing sources {e.g. QSOs}. Currently,
uncertainties in dN/dz and f{N} are the greatest sources of
uncertainty for inferring the shape and intensity of the UV background
radiation field. Second, we will estimate the amount of metals in the
LLS using the f{N} and ground based observations of metal line
transitions. It is possible that a significant fraction of the
"missing metals" at z~2 are associated with these highly ionized
absorbers. Third, analysis of the LLS lends to investigations of the
interface between galaxies {i.e. the damped Lyman alpha systems} and
the intergalactic medium {i.e. the Lyman alpha forest}. This survey is
ideal for a snapshot observing program, because the on-object
integration times are less than 10 minutes, and the targets cover the
majority of the northern sky.

ACS/HRC 11041

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This programme will be
for the entire lifetime of ACS. For cycle 15 the program will cover 18
months 12.1.06-05.31.08 and it has been divied into three different
proposal each covering six months. The three proposals are
11041-11042-11043.

ACS/SBC 10840

The FUV fluxes of Tauri stars in the Taurus molecular cloud

Present and forthcoming ground-based and space surveys of the T Tauri
stars in the Taurus molecular cloud will provide information from high
energy stellar and accretion radiation to low energy solid state and
molecular emission from the disk, making those stars perfect
laboratories to carry out self-consistent studies of disk physics and
evolution. We propose to complete this wealth of information by
obtaining ACS/FUV spectra for a significant sample of Taurus T Tauri
stars, covering a range of accretion properties and dust evolutionary
stages. FUV fluxes carry ~ 10 - 100 more energy than X-rays into these
disks and are thus crucial gas heating agents and key to disk
dispersal by photoevaporation. These observations are a pre-requisite
to interpret observations with Spitzer, SOFIA, Herschel, and ALMA, and
will become one of the important legacies of HST to the star formation
community.

ACS/WFC 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.

ACS/WFC 10886

The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

As a continuation of the highly successful Sloan Lens ACS {SLACS}
Survey for new strong gravitational lenses, we propose one orbit of
ACS-WFC F814W imaging for each of 50 high- probability strong
galaxy-galaxy lens candidates. These observations will confirm new
lens systems and permit immediate and accurate photometry, shape
measurement, and mass modeling of the lens galaxies. The lenses
delivered by the SLACS Survey all show extended source structure,
furnishing more constraints on the projected lens potential than
lensed-quasar image positions. In addition, SLACS lenses have lens
galaxies that are much brighter than their lensed sources,
facilitating detailed photometric and dynamical observation of the
former. When confirmed lenses from this proposal are combined with
lenses discovered by SLACS in Cycles 13 and 14, we expect the final
SLACS lens sample to number 80--100: an approximate doubling of the
number of known galaxy-scale strong gravitational lenses and an
order-of-magnitude increase in the number of optical Einstein rings.
By virtue of its homogeneous selection and sheer size, the SLACS
sample will allow an unprecedented exploration of the mass structure
of the early-type galaxy population as a function of all other
observable quantities. This new sample will be a valuable resource to
the astronomical community by enabling qualitatively new strong
lensing science, and as such we will waive all but a short {3-month}
proprietary period on the observations.

ACS/WFC/WFPC2 10890

Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous
Galaxies

The formative phase of the most massive galaxies may be extremely
luminous, characterized by intense star- and AGN-formation. Till now,
few such galaxies have been unambiguously identified at high redshift,
restricting us to the study of low-redshift ultraluminous infrared
galaxies as possible analogs. We have recently discovered a sample of
objects which may indeed represent this early phase in galaxy
formation, and are undertaking an extensive multiwavelength study of
this population. These objects are bright at mid-IR wavelengths
{F[24um]0.8mJy}, but deep ground based imaging suggests extremely
faint {and in some cases extended} optical counterparts {R~24-27}.
Deep K-band images show barely resolved galaxies. Mid-infrared
spectroscopy with Spitzer/IRS reveals that they have redshifts z ~
2-2.5, suggesting bolometric luminosities ~10^{13-14}Lsun! We propose
to obtain deep ACS F814W and NIC2 F160W images of these sources and
their environs in order to determine kpc-scale morphologies and
surface photometry for these galaxies. The proposed observations will
help us determine whether these extreme objects are merging systems,
massive obscured starbursts {with obscuration on kpc scales!} or very
reddened {locally obscured} AGN hosted by intrinsically low-luminosity
galaxies.

FGS 10928

Calibrating Cosmological Chronometers: White Dwarf Masses

We propose to use HST/FGS1R to determine White Dwarf {WD} masses. The
unmatched resolving power of HST/FGS1R will be utilized to follow up
four selected WD binary pairs. This high precision obtained with
HST/FGS1R simply cannot be equaled by any ground based technique. This
proposed effort complements that done by CoI Nelan in which a sample
of WDs is being observed with HST/FGS1R. This proposal will
dramatically increase the number of WDs for which dynamical mass
measurements are possible, enabling a better calibration of the WD
mass-radius relation, cooling curves, initial to final mass relations,
and ultimately giving important clues to the star formation history of
our Galaxy and the age of its disk as well as in other galaxies.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

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 images. Each observation will need its
own CRMAP, as different SAA passages leave different imprints on the
NICMOS detectors.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.)

HSTARS:

10546 - REAcq (1,2,2) failed to RGA Control

At AOS (340/21:38:00) REAcq (1,2,2) scheduled at 340/21:03:59-21:11:27
had failed to RGA control due to QSTOP flag on FGS 1. OBAD #1 data
unavailable due to LOS. OBAD #2: V1 1.45, V2 -16.24, V3 0.25, RSS
16.30 OBAD MAP: not scheduled

10547 - ACS 779 Fold Mechanism Move was Blocked

Status Buffer Message ACS 779 (X2)(Fold mechanism move was blocked)
was received at AOS (340/21:38:00). #1: P=0 T=40145, #2: P=0 T=50865.
The REAcq at 340/21:03:59 had failed so TDF was down when the fold
mechanism move to the SBC position was commanded. The move is blocked
and the SBC MAMA HV will remain on. The MAMA HV remaining on is a new
feature for ACS FSW CS4.01.

10548 - GSAcq(1,3,3) results in fine lock backup (1,0,1)

The GSAcq(1,3,3) scheduled at 341/08:34:19 - 08:42:24 resulted in fine
lock backup (1,0,1) using FGS-1 due to (QF3SSLEX) scan step limit
exceeded on FGS-3. Pre-acquisition OBADs showed (RSS) attitude
correction values of 2463.26 and 4.14 arcseconds. Post-acquisition
OBAD/MAP had 3-axis (RSS) value of 8.30 arcseconds.

COMPLETED OPS REQUEST:
17961-1 - RMGA Calibration for December 2006

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 08 08
FGS REacq 04 03
OBAD with Maneuver 26 26

SIGNIFICANT EVENTS:

Flash Report: RMGA Calibration Dec 2006

OPS Request 17969 was successfully executed on December 6, 2006 to
perform an RMGA Calibration test. RMGA was powered on at 340/20:40:52.
PSEA testmode was executed from 340/21:45 to 340/22:28 to collect RMGA
analog drift rate data for bias estimates. This data collection period
was about 44 minutes (22 iterations of PSEA testmode) and will be
processed by SAC. Assessment will determine if the drift rates have
changed enough to warrant a bias update in PSEA configuration memory.