Status Report

NASA Hubble Space Telescope Daily Report # 3783

By SpaceRef Editor
January 26, 2005
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NASA Hubble Space Telescope Daily Report # 3783

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT       # 3783



ACS 10140

Identification of a magnetic anomaly at Jupiter from satellite

Repeated imaging of Jupiter’s aurora has shown that the northern main
oval has a distorted ‘kidney bean’ shape in the general range of
90-140? System III longitude, which appears unchanged since 1994.
While it is more difficult to observe the conjugate regions in the
southern aurora, no corresponding distortion appears in the south.
Recent improved accuracy in locating the satellite footprint auroral
emissions has provided new information about the geometry of Jupiter’s
magnetic field in this and other areas. The study of the magnetic
field provides us with insight into the state of matter and the
dynamics deep down Jupiter. There is currently no other way to do this
from orbit. The persistent pattern of the main oval implies a
disturbance of the local magnetic field, and the increased latitudinal
separation of the locus of satellite footprints from each other and
from the main oval implies a locally weaker field strength. It is
possible that these phenomena result from a magnetic anomaly in
Jupiter’s intrinsic magnetic field, as was proposed by A. Dessler in
the 1970’s. There is presently only limited evidence from the scarcity
of auroral footprints observed in this longitude range. We propose to
obtain HST UV images with specific observing geometries of Jupiter to
determine the locations of the auroral footprints of Io, Europa, and
Ganymede in cycle 13 to accurately determine the magnetic field
geometry in the suggested anomaly region, and to either confirm or
refute the suggestion of a local magnetic anomaly.

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 10420

The assembly of a massive galaxy cluster: The 4/h Mpc filament feeding

We propose a deep ACS/WFC F606W+F814W mosaic of the massive cluster
MACSJ0717.5+3745 at z=0.55 in order to obtain the first direct
detection of cluster evolution through infall of matter along
large-scale filaments. Existing optical, X-ray, and groundbased
weak-lensing data show strong evidence of galaxy groups and dark
matter in a coherent structure spanning at least 10 arcmin {4/h Mpc,
LCDM} in the plane of the sky. The size of this object rules out prior
interaction between the groups and the cluster, thus making it a prime
candidate for a genuine filament as opposed to a merger remnant. The
proposed observation will 1} allow the first direct measurement of the
dark matter content and mass distribution along a large-scale filament
via weak lensing, and 2} provide, through galaxy morphology and
resolved color information, unprecedented insights into the physical
processes and environmental effects governing the transition from
field to cluster galaxies.

ACS/WFC 10429

Streaming Towards Shapley: The Mass of the Richest Galaxy
Concentration in the Local Universe

The 600 km/s motion of the Local Group {LG} with respect to the cosmic
microwave background {CMB} is now known to high accuracy. However, its
precise origin remains poorly understood. The contribution to the
motion from the pull of the rich Shapley supercluster at z = 0.048 is
particularly controversial. This extreme mass concentration contains
more than 20 Abell clusters within 35 Mpc of its very rich central
cluster A3558, and is recognized as both the optically richest and the
most X-ray luminous structure in the local {z < 0.1} universe. Yet, published values for the mass of Shapley continue to differ by an order of magnitude, and recent estimates of its pull on the LG range from negligible {20 km/s} to highly significant {300 km/s or more}. Here we propose to resolve this key issue by using ACS to measure high-precision surface brightness fluctuation {SBF} distances in order to make a direct measurement of the infall towards Shapley. We will target three Shapley foreground clusters where the infall is expected to be high {possibly 1000 km/s or more}, as well as the Shapley core, in order to test the assumption that it is at rest in the CMB. Prior to ACS, the Shapley region was unreachable for SBF, but ACS doubles the distance range of the SBF method with HST, enabling the distances to be measured to the required accuracy. The proposed measurements will place a firm limit on the largest mass fluctuation in the nearby universe and finally determine its contribution to the observed CMB dipole.

WFPC2 10132

UV Confirmation of New Quasar Sightlines Suitable for the Study of
Intergalactic Helium

The reionization of intergalactic helium is thought to have occurred
between redshifts of about 3 and 4. The study of HeII Lyman-alpha
absorption towards a half-dozen quasars at 2.72.9 SDSS quasars, but with special
emphasis on extending helium studies to the highest redshift
sightlines. Our proposed approach has already proven successful, and
additional sightlines will enable follow-up spectral observations to
measure the spectrum and evolution of the ionizing background
radiation, the density of intergalactic baryons, and the epoch of
reionization of the IGM.

WFPC2 10356

WFPC2 Cycle 13 Decontaminations and Associated Observations

This proposal is for the monthly WFPC2 decons. Also included are
instrument monitors tied to decons: photometric stability check, focus
monitor, pre- and post-decon internals {bias, intflats, kspots, &
darks}, UV throughput check, VISFLAT sweep, and internal UV flat


Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.) None



                             SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS Gsacq                   6                        6
FGS Reacq                   10                      10
FHST Update                 4                        4


A Target of Opportunity (TOO) SMS is being planned to provide two
visits to Target 10182 (PI Alex Filippenko; Titled “Towards a
Comprehensive Understanding of Type Ia Supernovae: The Necessity of UV
Observations” D1 and E1 on DOY 028 (Friday 1/28/5) with follow up
visits in next SMS 031. The intercept SMS products are expected to be
delivered on Thursday 1/27/5.

SpaceRef staff editor.