Update on the SKA

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Update on the SKA

• Richard Schilizzi
• International SKA Project Office
• SKA Wide-Field Imaging Workshop, Dwingeloo, 22
  June 2005

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Square Kilometre Array

• extremely powerful survey telescope at radio
  wavelengths - capability to follow up
  individual objects with high angular and time
  resolution
• 1 km2 collecting area sensitivity 50 x EVLA
  
  - survey speed is 10000 x faster than EVLA
• wide frequency range 0.1 25 GHz (goal)
• wide field of view 1 sq. degree at 1.4 GHz (5
  x area of moon) -
  goal many tens of sq. deg.

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Square Kilometre Array

• goal of multi-beam instrument at lower
  frequencies
• construction cost 1000 M operating cost 100 M
  per year
• born global gt50 institutes in 17 countries
  actively involved

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Key Science Projects

• probing the dark ages before the universe lit up
  
• the evolution of galaxies and large scale
  structure in the universe (equation of state of
  dark energy)
• strong field tests of gravity using pulsars and
  black holes
• the origin and evolution of cosmic magnetism
• the cradle of life movies of planetary
  formation ETI
• exploration of the unknown
• SKA science case (eds C. Carilli, S Rawlings)
  published by Elsevier in New Astronomy Reviews,
  vol 48, pp989-1163, December 2004
  (see also www.skatelescope.org)

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Equation of state of dark energy via HI surveys
with SKA

• dark energy alters distance measures in cosmology
  
• power spectrum of the clustering of galaxies
  likely to contain a signature of acoustic
  oscillations seen in the CMB at time of
  recombination
• use scale of acoustic oscillations as a
  cosmological standard ruler to measure equation
  of state of dark energy at intermediate redshift
  and possibly its evolution. 0.5ltzlt1.5 optimal
• evolution of the HI content of the universe.

CMB
SKA HI surveys
from C. Blake, S. Rawlings et al
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SKA pulsar survey
expect 20000 psrs incl. 1000 MSPs and
BH-pulsar binaries
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Cosmic Magnetism
From Rainer Beck and Bryan Gaensler
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Science requirements on FoV

• Contiguous imaging FoV
• 1 square degree within half power points at 1.4
  GHz, scaling as ?2
• 200 sq. deg. within half power points at 0.7 GHz,
  scaling as ?2 between 0.5-1.0 GHz
• Note The 1 square degree FoV is required by all
  key science projects. The 200 square degree FoV
  for 0.5-1.0 GHz is required by the dark energy
  key science project.
• Number of separated FoV
• 1 with full sensitivity Goal 4 with full
  sensitivity
• 10 simultaneous sub-arrays
• Note One FoV is required for all projects
  (obviously). None require more than a single FoV,
  but most would benefit from this (especially the
  large surveys) and it would dramatically increase
  the general observational flexibility of the SKA.
  

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Science requirements on data processing

• Correlator and post- correlation processing
• Imaging of 1 sq. degree at 1.4 GHz with 0.1
  arcsec angular resolution
• Imaging of 200 sq. degrees at 0.7 GHz with 0.2
  arcsec angular resolution
• Note Full field (but not full resolution)
  imaging requirements needed for
• pulsars, galaxy origins, magnetic universe, and
  dark energy
• Imaging of 104 separate regions within the FoV,
  each covering at least 105 beam areas at full
  (maximum baseline) angular resolution
• Note High angular resolution requirement
  needed for
• pulsars, galaxy origins, and cradle of life
• ( AGN/jets, astrometry, and imaging of stars,
  solar system objects, and maser sources)
• Spectral resolution of 104 channels per observing
  band per baseline
• Requirement for 104 spectral channels
• adequate velocity resolution over wide
  bandwidths for dark energy

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Large Mosaics (Robert Braun)

• Historically interferometric imaging was
  constrained to a single primary beam, but large
  WSRT mosaics are now routine.
• eg. WSRT HI mosiac of M31
• 163 pointings on 15 arcmin
• Nyquist-sampled grid
• 350 hours observing
• Aug. 2001 Jan. 2002
• 50 pc x 2 km/s res. over the 80 kpc disk
• s 1.4 mJy/Beam (at DV 2 km/s)
• DNHI 1.0, 3.5, 11 and 24 x 1018cm-2
• _at_ 120, 60, 30 and 20 (DV20 km/s)
• extended rotation curve / warping
• outer HI edge / UV radiation field
• CNM / WNM in disk
• circum-galactic HI clouds and streams

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SKA Concept
up to at least 3000 km from inner array
100-150
Software controlmonitoringcorrelation
calibration image formation archiving
scheduling
2000 antennas
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SKA in Australia
20 of total collecting area within 1 km diameter
50 of total collecting area within 5 km
diameter 75 of total collecting area
within 150 km from core
maximum baselines at least 3000 km from array
core
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SKA in Argentina
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(Landsat)
SKA in China
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(No Transcript)
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RFI equipment
ASTRON
Australia
China
South Africa
Argentina
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Antenna concepts

• Small diameter dishes ( Focal Plane Arrays)
• Aperture phased arrays
• Large diameter reflecting flux concentrators

Aperture array tiles
Small dishesFPAs in the focus
Small dishes
Spherical telescopes
Large adaptive reflectors
Major technical challenge for the SKA
reduce cost/m2
by a factor of 10 compared with current telescopes
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Antenna innovations

• Low-cost dense arrays for aperture and focal
  planes
• Active surfaces for large reflectors
• Broadband feeds
• Suspended or airborne inertial feed platform
• Cheap, accurate 12m dishes using hydroforming or
  preloading

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SKA development funds

• 50 M spent or committed to SKA development
  around the world since 1995.
• Recent initiatives xNTD (Australia), KAT (South
  Africa)
• In negotiation
• SKADS EMBRACE 2PAD (EU FP6 (10.4M)
  matching total 35-40M, 2005-9)
• Current proposals for funds
• Small Dishes SKA Technology Development Program
  (NSF US 31M, 2005-9)
• Large Adaptive Reflector - LAR Technical
  Development (NRC CA 12M, 2005-9)
• Development via SKA pathfinders comes for free
  telescopes
  that are precursors to the SKA and will prove
  major technology components for the SKA, eg
  LOFAR, EVLA, Allen Telescope Array, eMERLIN,
  eEVN,

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International timeline

• 1995-2008 technology prototyping
• 2005 site testing
• 2006 site ranking decision (September)
• 2007 major external review of technical designs
• 2009 final technical design selection
• 2009 submit proposals for phased development of
  SKA
• 2010 start construction of Phase 1 on selected
  site
• 2013 implementation readiness review for full
  array
• 2014 start construction of full array
• 2020 complete construction

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