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The Square Kilometer Array: Introduction and Current Developments Jim Cordes, Cornell University

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Title: The Square Kilometer Array: Introduction and Current Developments Jim Cordes, Cornell University


1
The Square Kilometer Array Introduction and
Current DevelopmentsJim Cordes, Cornell
University
  • The SKA Project
  • SKA science case
  • Fundamental questions in physics, astrophysics
    and astrobiology
  • Unprecedented capacity for discovery
  • International and US activity
  • Issues
  • Siting
  • Finance
  • Phased deployment
  • Rescoping

2
SKA What is It?
  • An array telescope that combines complete
    sampling of the time, frequency and spatial
    domains with a ?20 to 50 increase in collecting
    area ( 1 km2) over existing telescopes.
  • Frequency range 0.1 25 GHz (nominal)
  • Limited gains from reducing receiver noise or
    increasing bandwidth on current arrays
  • Innovative design needed to reduce cost
  • 106 meter2 ? 1,000 per meter2
  • c.f. existing arrays 10,000 per meter2
  • An international project from the start
  • International funding
  • Cost goal 1 billion
  • 17-country international consortium
  • Executive, engineering, science, siting,
    simulation groups
  • Timeline for construction extends to 2020
  • Can be phased for different frequency ranges
  • Can do science as you build (go as you grow)

3
Science with the Square Kilometer Arrayedited
by Chris CarilliSteve RawlingsSpecial issue
of New Astronomy ReviewsVolume 48, December
2004, 979-1605(48 chapters)
  • Five key science projects
  • Discovery science
  • Enabling understanding in fundamental physics
    and origins

4
Five Key Science Areas for the SKA
Topic Goals
Probing the Dark Ages 1. Map out structure formation using HI from the era of reionization (6 lt z lt 13) 2. Probe early star formation using high-z CO 3. Detect the first active galactic nuclei
Gravity Pulsars Black Holes 1. Precision timing of pulsars to test theories of gravity approaching the strong-field limit (NS-NS, NS-BH binaries, incl Sgr A) 2. Millisecond pulsar timing array for detecting long-wavelength gravitational waves
Cosmic Structure 1. Understand dark energy e.g. eqn. of state W(z) 2. Understand structure formation and galaxy evolution 3. Map and understand dark matter
Cosmic Magnetism Determine the structure and origins of cosmic magnetic fields (in galaxies and in the intergalactic medium) vs. redshift z
The Cradle of Life 1. Understand the formation of Earth-like planets 2. Understand the chemistry of organic molecules and their roles in planet formation and generation of life 3. Detect signals from ET
5
Was Einstein Right About Gravity?The SKA as a
Pulsar/Gravity Machine
  • Relativistic binaries (NS-NS, NS-BH) for probing
    strong-field gravity
  • Orbit evolution propagation effects of pulsars
    near Sgr A
  • Millisecond pulsars lt 1.5 ms (EOS)
  • MSPs suitable for gravitational wave detection
  • 100s of NS masses (vs. evolutionary path, EOS,
    etc)
  • Galactic tomography of electron density and
    magnetic field definition of Milky Ways spiral
    structure
  • Target classes for multiwavelength and non-EM
    studies (future gamma-ray missions, gravitational
    wave detectors)

Millisecond Pulsars
Relativistic Binaries
Today
Today
Future
Future
SKA
SKA
Blue points SKA simulation Black points known
pulsars
only 6!
104 pulsar detections
6
Flowdown from SKA Science to Technical
Requirements
Topic Type of Obs. Freq. (GHz) Baselines Special Requirements
Dark Energy Cosmic Structure M galaxies at z2 0.3 1.4 300 Large FOV for survey speed
Gravity Pulsars Black Holes Full Galactic Census Precision Timing Extragalactic pulsars 0.5 15 GHz Core lt few km Extended gt3000 km Full SKA for extragalactic Full FOV fast sampling
Probing the Dark Ages HI structure 6 lt z lt 13 CO at zgt6 The first AGNs 0.1 - 20 100 to gt 3000 to 35 GHz for CO
Cosmic Magnetism Faraday rotation of 108 extragalactic sources 0.3 - 10 300 -40dB polarization purity
The Cradle of Life protoplanetary disks SETI gt20 0.5-11 gt 3000 Multiple beams
7
SKA Frequencies and Technologies
8
Surveys past, present and future
9
The Collecting Area Plateau in Radio Astronomy
  • Increased collecting area enables
  • Detection of L galaxies in HI at z 2
  • Epoch of Reionization analysis
  • GRB afterglows ?100 fainter than currently
  • Detection/timing of pulsars near Sgr A
  • Gap structure in young, protoplanetary disks

Recent growth in sensitivity has exploited
low-noise devices, developments in digital signal
processing bandwidth, and calibration and imaging
techniques.
10
The 6th Key Science AreaExploration of the
Unknown
  • Todays hot new issues are tomorrows old issues.
  • The excitement of the SKA will not be just the
    old questions it will answer but in the new
    questions it will raise.
  • We build telescopes for discovery and
    understanding. What is the right mix?

Entirely new classes of objects and phenomena
will be discovered if the SKA has appropriate
flexibility in its operations (digital signal
processing capabilities, array configuration,
field of view, etc.)
c.f. Exploration of the Unknown, Wilkinson et al.
in SKA science book
11
Key Discoveries that Illustrate Discovery Space
in Radio Astronomy
Discovery Date Enabled by Telescope
Cosmic radio emission 1933 ? Bruce Array (Jansky)
Non-thermal radio emission 1940 ? Reber antenna
Solar radio bursts 1942 ?, ?t Radar antennas
Extragalactic radio sources 1949 ?? Australia cliff interferometer
21 cm line of hydrogen 1951 theory, ?? Harvard horn antenna
Mercury and Venus spin rates 1962, 1965 Radar Arecibo
Quasars 1962 ?? Parkes occultation
Cosmic Microwave Background 1963 ?S, calibration Bell Labs horn
Confirmation of General Rel. 1964, 1970s theory, radar, ?t, ?? Arecibo, Goldstone, VLA,VLBI
Cosmic masers 1965 ?? UC Berkeley, Haystack
Pulsars 1967 ?, ?t Cambridge 1.8 hectare array
Superluminal motions in AGNs 1970 ?? Haystack-Goldstone VLBI
Intersteller molecules and GMCs 1970s theory, ?,?? NRAO 36ft
Binary neutron stars and gwaves 1974-present ?, ?t Arecibo
Gravitational lenses 1979 theory, ?? Jodrell Bank interferometer
First extrasolar planet system 1991 ?, ?t Arecibo
Size of GRB fireball 1997 ??, ?S, theory VLA
12
Nobel Prizes from the Discovery Space in Radio
Astronomy
Discovery Date Enabled by Telescope
Cosmic radio emission 1933 ? Bruce Array (Jansky)
Non-thermal radio emission 1940 ? Reber antenna
Solar radio bursts 1942 ?, ?t Radar antennas
Extragalactic radio sources 1949 ?? Australia cliff interferometer
21 cm line of hydrogen 1951 theory, ?? Harvard horn antenna
Mercury and Venus spin rates 1962, 1965 Radar Arecibo
Quasars 1962 ?? Parkes occultation
Cosmic Microwave Background 1963 ?S, calibration Bell Labs horn
Confirmation of General Rel. 1964, 1970s theory, radar, ?t, ?? Arecibo, Goldstone, VLA,VLBI
Cosmic masers 1965 ?? UC Berkeley, Haystack
Pulsars 1967 ?, ?t Cambridge 1.8 hectare array
Superluminal motions in AGNs 1970 ?? Haystack-Goldstone VLBI
Intersteller molecules and GMCs 1970s theory, ?,?? NRAO 36ft
Binary neutron stars and gwaves 1974-present ?, ?t Arecibo
Gravitational lenses 1979 theory, ?? Jodrell Bank interferometer
First extrasolar planet system 1991 ?, ?t Arecibo
Size of GRB fireball 1997 ??, ?S, theory VLA
13
Combine Greater Sensitivity with Wide Field of
View Processing
The SKA combines a gt ?20 boost in sensitivity
with unprecedented utilization of the field of
view
14
The International SKA Project
  • International SKA Project Office (ISPO)
  • Richard Schilizzi (Director)
  • Peter Hall (Project Engineer)
  • Project Scientist (TBD)
  • Is conducting site testing in advance of site
    selection
  • International SKA Steering Committee (ISSC)
  • 21 total members (7 Europe, 7 US, rest of the
    world)
  • Working groups Science, Simulations, Site
    Evaluation, Engineering, Operations, Outreach
  • Advisory Committees (Science, Site Selection, )

15
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16
Siting the SKA
  • Current siting decision is late 2006 (ISPO)
  • Argentina, Australia, China, South Africa
    proposals expected by end of 2005
  • Working plan single site for all frequencies,
    covered with 2 to 3 antenna technologies (subject
    to optimization vs. cost/performance)
  • Dipoles ? 0.3 GHz
  • Aperture array or dishes 0.3 ? 2 GHz
  • Paraboloids 1 ? 25 GHz
  • US perspective good to explore alternatives to a
    single-site
  • SKA low-frequency array in southern hemisphere
  • radio quiet zone
  • ? 2 GHz
  • SKA high-frequency array built upon the EVLAVLBA
    ??
  • Better tropospheric properties than some southern
    sites, RFI less an issue
  • leverages existing investments
  • recognizes international utilization of EVLA,
    VLBA
  • Proposed by the US SKA Consortium to the
    International SKA Steering Committee as a
    Discussion Document (2005 April)

17
Discussion Issues
  • Design and usage issues for the SKA
  • Phased deployment of the SKA vs. frequency?
  • Tradeoffs between science goals and cost?
  • Size of core array usable for searching?
  • Polarization calibration across wide FOV
  • How to deal with the huge number of new pulsars
  • Time only the best after initial quick
    assessment?
  • Require multibeam capability?

18
Discussion Issues
  • Astropolitics
  • SKA science case needs continual promotion
  • Need to jointly promote gravity studies
  • Laboratory and spacecraft gravitational wave
    detectors
  • Pulsars as clocks and gravitational laboratories
  • Sometimes perceived as having no connection
    and/or in competition
  • Joint SKA and LISA meeting?

19
SKA Development in the US
  • US Concept Large-N/Small-D (LNSD)
  • The US SKA Consortium prepares whitepapers on the
    LNSD concept for consideration by the
    International SKA Steering Committee and also for
    a SW US high-frequency SKA site
  • Allen Telescope Array
  • Low-frequency arrays (MWA, LWA) science and
    technology precursors
  • Deep Space Network Array closely related to US
    SKA concept, strong possibilities for economies
    of scale
  • Explicit SKA development
  • NSF ATI Grant (1.5M) 2002-2005
  • Technology Development Project (TDP)
  • 32M over 5 years (NSF proposal pending)
  • End to end development, costing, preliminary
    design
  • Organized through the US SKA Consortium (17
    institutions)
  • Managed by NAIC/Cornell
  • Facilitates and unifies SKA development at NRAO,
    NAIC, and institutions involved with
    low-frequency array development
  • The next steps await outcome of the NSFs Senior
    Review (Spring 2006)

20
Further
  • The SKA is still TBD with respect to design,
    science emphasis, feasibility, funding
  • The SKA is in fierce competition for funding all
    around the world
  • We need to promote the pulsar/gravity KSP as
    strongly as possible
  • The KSPs are not frozen categories creatively
    enhance or supplant them!

21
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