Daily 3876

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 3876

PERIOD COVERED: UT June 07, 2005 (DOY 158)

OBSERVATIONS SCHEDULED

ACS/HRC 10182

Towards a Comprehensive Understanding of Type Ia Supernovae: The
Necessity of UV Observations

Type Ia supernovae {SNe Ia} are very important to many diverse areas
of astrophysics, from the chemical evolution of galaxies to
observational cosmology which led to the discovery of dark energy and
the accelerating Universe. However, the utility of SNe Ia as
cosmological probes depends on the degree of our understanding of SN
Ia physics, and various systematic effects such as cosmic chemical
evolution. At present, the progenitors of SNe Ia and the exact
explosion mechanisms are still poorly understood, as are evolutionary
effects on SN Ia peak luminosities. Since early-time UV spectra and
light curves of nearby SNe Ia can directly address these questions, we
propose an approach consisting of two observational components: {1}
Detailed studies of two very bright, young, nearby SNe Ia with HST UV
spectroscopy at 13 epochs within the first 1.5 months after discovery;
and {2} studies of correlations with luminosity for five somewhat more
distant Hubble-flow SNe Ia, for which relative luminosities can be
determined with precision, using 8 epochs of HST UV spectroscopy
and/or broad-band imaging. The HST data, along with extensive
ground-based optical to near-IR observations, will be analyzed with
state-of-the-art models to probe SN Ia explosion physics and constrain
the nature of the progenitors. The results will form the basis for the
next phase of precision cosmology measurements using SNe Ia, allowing
us to more fully capitalize on the substantial past {and future}
investments of time made with HST in observations of high-redshift SNe
Ia.

ACS/HRC 10377

ACS Earth Flats

High signal sky flats will be obtained by observing the bright Earth
with the HRC and WFC. These observations will be used to verify the
accuracy of the flats currently used by the pipeline and will provide
a comparison with flats derived via other techniques: L-flats from
stellar observations, sky flats from stacked GO observations, and
internal flats using the calibration lamps. Weekly coronagraphic
monitoring is required to assess the changing position of the spots.

ACS/WFC 10325

Low Redshift Cluster Gravitational Lensing Survey

This proposal has two main scientific goals: to determine the dark
matter distribution of massive galaxy clusters, and to observe the
high redshift universe using these clusters as powerful cosmic
telescopes. Deep, g, r, i, z imaging of a sample of low-z {0.2-0.4}
clusters will yield a large sample of lensed background galaxies with
reliable photometric redshifts. By combining strong and weak lensing
constraints with the photometric redshift information it will be
possible to precisely measure the cluster dark matter distribution
with an unprecedented combination of high spatial resolution and area
coverage, avoiding many of the uncertainties which plague ground-based
studies and yielding definitive answers about the structure of massive
dark matter haloes. In addition, the cosmological parameters can be
constrained in a largely model independent way using the multiply
lensed objects due to the dependence of the Einsteinng ring radius on
the distance to the source. We can also expect to detect several
highly magnified dropout galaxies behind the clusters in the redshift
ranges 4-5 5-6 and 7-8, corresponding to a drop in the flux in the g,
r, and i bands relative to longer wavelength. We will obtain the best
information to date on the giant arcs already known in these clusters,
making possible detailed, pixel-by-pixel studies of their star
formation rate, dust distribution and structural components, including
spiral arms, out to a redshift of around z~2.5 in several passbands.

NIC1/NIC2/NIC3 8792

NICMOS Post-SAA calibration - CR Persistence Part 3

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.

NIC2 10167

Imaging of Ices in Circumstellar Disks

The link between the material of the interstellar medium and the
ultimate composition of planets lies in the way gas and dust are
processed in circumstellar disks. Planet formation models rely upon a
knowledge of the disk constituents and temperature profiles to
simulate how small grains eventually combine into terrestrial planets
and gas giant cores. Disks around other stars may be analogs for our
own early Solar System and thus allow the direct measurement of such
phenomena. Only recently, however, have well-resolved images of dust
disks around several late T Tauri or main sequence stars been secured.
HST provides a uniquely stable platform for making such sensitive high
dynamic range images. Now, for those handful of disks already
resolved, we are able to go beyond the discovery phase and begin
making astrophysical measurements to deepen our understanding of the
course of disk evolution. We therefore propose a multi-wavelength
study with NICMOS designed to discover the spatial distribution of two
common Solar System materials -- methane and water ices -- in other
systems.

NIC3/WFPC2/ACS/WFC 10131

Determining the Origin of Virgo's Intracluster Stars

Intracluster stars constitute about 20% of the total stellar
population of a typical galaxy cluster, and their existence provides a
vital clue for our understanding of cluster formation and evolution.
However, to exploit their probative value, we need to know their
origins: are they the remnants of dwarf galaxies, long since destroyed
by the cluster potential, or have the stars been harassed from their
parent galaxies at recent epochs? To answer this question, we propose
to use the Wide-Field Channel of ACS to make an I, {V-I}
color-magnitude diagram of Virgo's intracluster stars. From the
position and morphology of the population's red giant branch, we will
be able to determine the metallicity distribution function of the
stars, and thereby determine their likely origin and ejection
mechanisms. Only HST with the ACS has the sensitivity and resolution
to perform this fundamental measurement. This program has two options.
Option one uses conventional methods of cluster photometry and
requires 37 orbits of exposure time. Option two involves a novel
analysis technique, which promises to achieve most of the same science
in two- thirds the time {23 orbits}. We describe this alternative
method of analysis and demonstrate its use via simulations.

WFPC2 10360

WFPC2 CYCLE 13 INTERNAL MONITOR

This calibration proposal is the Cycle 13 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
{gain 7 and gain 15}, a test for quantum efficiency in the CCDs, and a
monitor for possible buildup of contaminants on the CCD windows.

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:
1345-0 - The Official Release of 6.7 for Realtime Ops @ 158/1130z
1346-0 - Execute CCL KEYMNEPS to Set EPS Red Limits @ 158/1250z
1347-0 - ACS FSW CS 4.01 (JV0017P01) Load Delivery @ 158/1645z
1348-0 - ACS FSW CS 4.01 @ 158/1645z


SCHEDULED SUCCESSFUL FAILURE TIMES
FGS Gsacq 06 06
FGS Reacq 06 06
FHST Update 11 11
LOSS of LOCK


SIGNIFICANT EVENTS: (None)