Square Kilometre Array: Project Overview

Richard SchilizziInternational SKA Project

Office

CERN21 January 2005

Outline

the SKA in 2 slides

why build it?

concept, site choice

technical issues

SKA governance, funding, and timeline

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 ~100 x currently most powerful telescope (VLA)

- survey speed is 10000 x faster than VLA

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.

Square Kilometre Array

goal of multi-beam instrument at lower frequencies

construction cost 1 B€; operating cost 50 M€ per year

“born global”; 45 institutes in 17 countries actively involved

The history of the universe

Actually, we dont know much

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)

Galaxies in optical light and atomic hydrogen

M81 in atomic hydrogen

M81 in optical light

Equation of state of dark energy via atomic hydrogen 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. 0.5<z<1.5 optimal

•evolution of the HI content of the universe.

CMB

SKA HI surveys

from C. Blake, S. Rawlings et al

Pulsars tell us about gravity

•…almost Black Holes•…objects of extreme matter •…relativistic plasma physics in action•…probes of turbulent and magnetized ISM•…precision tools, e.g. - Period of B1937+21: P = 0.0015578064924327 0.0000000000000004 s Orbital eccentricity of J1012+5307: e<0.0000008•…testing ground for theories of gravity – pulsar-black hole binary•…cosmological gravitational wave detectors

Watch planets forming

Hubble Space Telescope: optical scattered light

Very Large Array: 7mm dust emission (radio)

Simulation of a gap in a protoplanetary disk caused by a forming planet

High sensitivity + high angular resolution required

Intelligent life elsewhere?

ATA

Phoenix

SKA

ATA

Phoenix

SKA

SKA as Search Engine

SKA Concept

Software: control&monitoringcorrelation calibration image formation archiving scheduling

up to at least 3000 km from inner array

~100

2000 antennas

Example SKA configuration

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

SKA in Argentina

(Landsat)

SKAin

China

KARST

Core @ VLA

SKA in North America

Antenna concepts

Large diameter reflecting flux concentrators

Small diameter dishes

Aperture phased arrays

Large adaptive reflectors Spherical telescopes Cylinders

Small dishes. I Small dishes.II Aperture array tiles

Major technical challenge for the SKA: reduce cost/m2 by a factor of 10 compared with current telescopes

Small dishes+aperture arrays in the focus

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

Data transport

High data rates– 1-2 Tb/s from stations desirable– 80 Gb/s from individual antennas in central array– “Commercially realistic” ~ 100 Gb/s for longer links– 100 Gb/s on trans-continental and trans-oceanic links allows ~ 1 “full” SKA image per minute (1TB) to be transported from imaging engine

Digital fibre links throughout array Information transport costs may dominate processing costs Local oscillator/timing is a challenge for a highly-distributed array

SKA Correlators Cross-correlation

(multiply-accumulate) is the basis of interferometry

1 MAC per sample Number of

correlations ~ N2 / 2 ~ 3 x 106

Inp. data rate ~ 3 PB/sMAC rate ~ 3 P op/s

Output data rate ~ 30 M correlations / s

Typical SKA Correlator

No. inputs(correlated entities)

N = 2500

Max.sig. Bandwidth

4 GHz

Sample rate

10 Gs/s

Input precision

8 bit

Output precision

~ 32 bit

Accumulate time

0.1 - 1 s

DSP or HPC?

DZB/Jive

SKA

LOFAR

Courtesy Eugene de Geus

Line between DSP and general purpose computers will be blurred

Post-correlation

Hardware Wide-field imaging is probably the cost driver

RFI mitigation could also be expensive

Calculate wide-field imaging costs in 2004 (from simulations) and scale with Moore’s LawAssume that ML holds for computing costs, not necessarily for per CPU costs

AND that we achieve large scale parallelization at good efficiency

Bottom line: perhaps aim for 100Pflops in 2015 for €100M If 100Pflops is beyond the state of the art in 2015, we’ll have to scale back our scientific ambitions until it is.

calibrationimagingarchivedistribution

CSKA : $3.5M

0.1

f

0.5

2B

5km

3D

12.5m

8 0.2m

500MHz

22 2010 t

3

Software

Estimating total software effort required is hard at this stage of the project

Projecting from ALMA (Atacama Large Millimeter Array) 1000 – 2000 fte

Projecting from LOFAR (Low Frequency Array) 250-500 fte

Technology

Project Management

Wideband, efficient antennas

Sensitive, low-cost receivers

Fast, long-distance, data transport

High performance DSP & computing hardware

New data processing and visualization techniques

Evolving science goals High levels of technical

risk International politics Ambitious delivery

timescale Industry liaison

Pre-competitive alliances + procurement + project delivery

Performance + Cost

SKA challenges

Who’s doing what around the world?

Europe SKA Design Study (SKADS); Pharos; LOFAR; eEVN; eMERLIN

USA NSF Technology Development Program; Allen Telescope Array; EVLA; potential site

Canada Canadian Large Adaptive Reflector

Australia small dishes+FPAs; potential site

India small dishes

China Five-hundred-metre Aperture Spherical Telescope FAST); potential site

Sth Africasmall dishes+FPAs; potential site

Argentinapotential site

SKA management structure

International SKA Steering Committee

Executive Committee

International Science Advisory

Committee

International Engineering

Advisory Committee

International Site Selection Advisory

Committee

Outreach Committee

Engineering Working Group

Site Evaluation

Working Group

Simulations Working Group

Science Working Group

International SKA Project Office

Operations Working Group

International Collaboration Working Group

8 task forces 2 task forces 1 task force6 task forces

SKA development funds

38 M€ committed to SKA development so far around the world

Current proposals for funds•Aperture Array Tiles – SKA Design Study (EU FP6 + matching: €38M, 2004-8)

•Small Dishes – SKA Technology Development Program (NSF: $US 31M, 2005-9)

•Small Dishes+AA – Australia (CSIRO: $AU 15M, 2005-8) -- South Africa (Government: R70M, 2005-8)

•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,…

International timeline

1995-2008 technology prototyping

2005 site testing

2006 site decision (September)

2007 major external review of technical designs

2009 select technical design (may be a combination)

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

SKA information

www.skatelescope.org

SKA newsletter 2x per year