the square kilometer array: introduction and current developments jim cordes, cornell university

16 Aug 2005 Jim Cordes: SKA: Introduction and CurrentJim Cordes: SKA: Introduction and Current Developments Developments

The Square Kilometer Array:The Square Kilometer Array: Introduction and Current Developments Introduction and Current Developments

Jim Cordes, Cornell UniversityJim 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

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SKA: What is It?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”)

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Science with the Square Kilometer ArrayScience with the Square Kilometer Array

edited by edited by Chris CarilliChris Carilli

Steve RawlingsSteve Rawlings

Special issue of New Astronomy ReviewsSpecial issue of New Astronomy ReviewsVolume 48, December 2004, 979-1605Volume 48, December 2004, 979-1605

(48 chapters)(48 chapters)

• Five key science projects

• Discovery science

• Enabling understanding in fundamental physics and origins


Five Key Science Areas for the SKAFive Key Science Areas for the SKATopic Goals

Probing the Dark Ages

1. Map out structure formation using HI from the era of reionization (6 < z < 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 Structure1. Understand dark energy [e.g. eqn. of state; W(z)]

2. Understand structure formation and galaxy evolution

3. Map and understand dark matter

Cosmic MagnetismDetermine 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


Was Einstein Right About Gravity?Was Einstein Right About Gravity?The SKA as a Pulsar/Gravity MachineThe 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 < 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 Way’s spiral structure• Target classes for multiwavelength and non-EM studies (future

gamma-ray missions, gravitational wave detectors)

Blue points: SKA simulationBlack points: known pulsars

Millisecond PulsarsMillisecond Pulsars Relativistic BinariesRelativistic Binaries

Today TodayFuture

SKASKA SKASKA

Future

only 6!~104 pulsar detections


Flowdown from SKA Science to Technical RequirementsFlowdown from SKA Science to Technical Requirements

Topic Type of Obs.Freq.

(GHz)Baselines

Special Requirements

Dark Energy & Cosmic Structure

M* galaxies at z=2 0.3 – 1.4 300Large FOV for survey speed

Gravity: Pulsars & Black Holes

Full Galactic Census

Precision Timing

Extragalactic pulsars

0.5 – 15

GHz

Core < few km

Extended >3000 km

Full SKA for extragalactic;

Full FOV fast sampling

Probing the Dark Ages

HI structure 6 < z < 13

CO at z>6

The first AGNs

0.1 - 20 100 to > 3000to 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

>20

0.5-11> 3000 Multiple beams


SKA Frequencies and TechnologiesSKA Frequencies and Technologies


The Collecting Area Plateau in Radio AstronomyThe Collecting Area Plateau in Radio Astronomy

Recent growth in sensitivity has exploited low-noise devices, developments in digital signal processing bandwidth, and calibration and imaging techniques.

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


The 6The 6thth Key Science Area: Key Science Area:Exploration of the UnknownExploration of the Unknown

• Today’s hot new issues are tomorrow’s 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


Discovery Date Enabled by TelescopeCosmic 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

Key Discoveries that Illustrate Discovery Space in Radio AstronomyKey Discoveries that Illustrate Discovery Space in Radio Astronomy


Discovery Date Enabled by TelescopeCosmic 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

Nobel Prizes from the Discovery Space in Radio Astronomy from the Discovery Space in Radio Astronomy


, , t, pol, , t

Large processing FOV

High sensitivity:

Combine Greater Sensitivity with Wide Field of View ProcessingCombine Greater Sensitivity with Wide Field of View Processing

The SKA combines a > 20 boost in sensitivity with unprecedented utilization of the field of view


The International SKA ProjectThe 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, …)


Siting the SKASiting 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 EVLA+VLBA ??» 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)


Discussion IssuesDiscussion 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?


Discussion IssuesDiscussion 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?


SKA Development in the USSKA Development in the USUS 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 NSF’s “Senior Review” (Spring 2006)


FurtherFurther• 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!

the square kilometer array: introduction and current developments jim cordes, cornell university

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