www.csiro.au

Pathfinders to the SKA — xNTD

Colin JackaProject Leader, NTD and xNTD Projects

Australian SKA Industry Cluster MeetingPerth, 6 December 2006

Development of Australia’s SKA Demonstrator

Australia

� Has a traditional strength in radioastronomy

� Has a unique radio-quiet environment

� Has a good view of the Southern sky

� Is engaged in a number of International SKA activities

� Has a strong and effective governance structure for SKA-related activities administered through the CSIRO ATNF

� Has proposed a candidate site for SKA

� Single country 3000 km E-W baseline (+NZ extension possible to 5500km)

� Has proposed a concept for its SKA Demonstrator (the xNTD) based on SD-FPAs

� Has confirmed financial support from CSIRO and Government

� Has an established vision towards SKA through its published technology and science roadmaps towards SKA

2000

Site

ranking

‘1% SKA’

Science

ISSC

MoAs

Site

Selection

Science

Case

published

Inter-governmental

discussions ***

First SKA

Working

Group

Initial concept

2000

‘10% SKA’

Science

92 96 04 05 06 07 08 09 10 14 18 22

Feasibility

study

Full array

Build

100% SKA

SKA

Complete

Phase 1

Build

10% SKA

Concept

exposition

Define SKA

SystemConstruct 1%

“pathfinders”

International SKA Timelineand Australia’s Pathfinder Roadmap

Adopt

Reference

Design

• NTD provides initial R&d for SD-FPA concept with digital beamforming

• xNTD demonstrates the FPA+small dish concept that could be adopted for the SKA core

� Must show that key performance and cost goals can be met

� And pave the way for SKA Phase 1 ― at Mileura WA

NTD xNTDSKA φ1

Q3 Q4 Q1 Q2

Development

of 6 antenna

working system

@ Mileura

Q3 Q4 Q1 Q2Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2

xNTD 5-year Project Roadmap

2006-2007

NTD FPA Research

Build

Testbed

antenna @

Parkes

Tender forTestbed antenna,

Tender for antenna design,

Assess composite materials

Development of 10 MHz Digital Beamformer CABB-based

correlator

New full xNTD correlator

RXs for prototypeRXs for xNTD, including:

(a) Participation in SOC RX solution for xNTD and SKA,

(b) Research into reducing Tsys (such as by using cooling of

LNAs)

Build rest of N (N=30) antennas @

Mileura

Data Trans for prototypeData Trans for

MileuraFurther Data Trans for Mileura

Full 300 MHz Beamformers

Concept Design ReviewPreliminary Design ReviewCritical Design Review

2007-2008 2008-2009 2009-2010 2010-2011

Commission 6

antennas

Science with

6 antennas

Commission N

antennas

Science with

N antennas

Smart Feeds Project (including research on using at higher frequencies)

Build 6 antennas

@ Mileura

Software (staged) for NTD, prototype @ Parkes, xNTD6 and xNTD30 @ Mileura

Infrastructure for Mileura

Infrastructure for

prototype

Testbed FPA

System

Development

@ Parkes

Development of (N=6+24)

xNTD system @ MileuraSystem Design

Operational Requirements Planning for xNTD

Jul 06

Jul 07

Jul 08

Jul 09

Jul 10

June 11

Stages of Technology Development in Australia

• 2002 – 2007; MNRF-funded projects

� MMIC: Development of RF-CMOS technology for Receiver on a chip

� CABB: Powerful new digital processors; demonstration as upgrade of ATCA facilities at Narrabri

� SKAMP — some alternative digital architectures being tried on the Molonglo telescope operated by Sydney University

� SKA siting — to determine the requirements for siting the SKA

� NTD — the integration of technologies into a system to verify and demonstrate that the SD-FPA concept can provide the wide FOV and multi-beaming capabilities required for SKA

• 2006 – 2010: xNTD; predominantly CSIRO-funded

� Extended version of NTD, at proposed SKA site (Mileura WA) that satisfies both:

� SKA technology demonstrator, basis for “SKA Phase 1”

� Operational telescope capable of new science

� Now with NCRIS funding and Canadian collaboration => MIRA

• Next Stage Pathfinder is 10% SKA

� Needs International funding, to be built where?, based on what technology?

� Could it be an extension to xNTD?

Staging of Challenges

NTD

� Development of FPAs with all-digital beamforming -FOV challenge

� FPA calibration and measurement methods

xNTD

� The antenna challenge – cost!

� FPA challenge – cost, bandwidth, performance

� The integrated Receiver – 1st cost reduction

� The correlator and beamforming challenges – cost, flexibility

� The post-correlator processing challenge

� The data transmission challenge

� Integration into a useful scientific instrument

SKA

� All of above – Cost!!! “Consumer” technology, mass production.

� Long haul data transmission

� Station beamforming

� Post correlator processing and imaging challenges – dynamic range, processing

NTD Status (at Marsfield)

A testbed for FPA development

• 2 element interferometer with 13.7 m antennas

• We have this in operation (July 06)

• THEA tile for initial FPA analysis

• 24-receiver system (discrete)

• 24-element, 24 MHz BW Digital Beamformer

• System integration and software

• Will be a testbed for our own FPA development concepts

• Constrained by the RFI in a big city

� But still much can be done (convenience to lab, rfimitigation)

NTD Technology

NTD Next steps (2007)

•Further measure and understand ThEA tile

•Canadian Vivaldi array on interferometer

•Prototype linear connected array on interferometer

•Usefulness is limited by RFI and collecting area but 1st order tests possible

� Efficiency, Tsys

� Noise covariance

� Beamformer tests

•Will extend NTD to Parkes interferometer (Sept 2007)

� 64 m + 12 m dishes

� Much more collecting area, less interference

� Sidelobe structure

Existing prototype receiver, beamformerCorrelators – Bunton, Grancea, et al

Some Technical Challenges for SKA

• the frequency range specs: 100 MHz to > 20 GHz

• Wide FOV; no single technology over that freq range

• Cost of basic antennas; xNTD has budget per antenna twice that for SKA

• The sensitivity requirement implies large collection area and extremely low-noise receiver front-ends, all at very low cost.

• The wide FOV implies large number of receivers, probably requires “receiver on a chip” technology

• Even the low-noise environment at Mileura will get effected by satellite signals, so we need to develop smart RFI mitigation techniques

Australia’s xNTD project will be tackling many of these

The xNTD– Wide FOV, fast surveying

Beamformer

Smart feed

Correlator

and further

processing

Multiple

beams

xNTD will have ~30 beams

Each beam ~1 sq deg

Wide field of view is ~ 30 sq deg

xNTD as a technology demonstrator

• xNTD is a telescope array of small dishes with smart feeds or collectors

• We suggest that the xNTD architecture could form the basis for a major part of the SKA

� applicable to being part of the “core”

� and also applicable as an “SKA station”

• We are developing solutions to significant challenges which need to be demonstrated

� Low cost dishes

� Smart electronic feeds/collectors

� Data transfer and computing

• xNTD needs to be a working astronomical instrument which demonstrates the key technological advances needed for the SKA

xNTD —Some Immediate Questions/Decisions

• Antennas:

� Purposes:

� Medium for FPA development in fairly quiet environment

� Prototype xNTD antenna

� xNTD Project Plan has decoupled these

� Testbed at Parkes (July-Sept 2007), COTS solution (from open tender process), alt-az, proven surface is best for prototyping (testbed), provides extra time to get xNTD antenna design right

� xNTD antennas: design studies proceeding in parallel, involvement of Canadian expertise (MIRA) with Australian industry, decision in Sept 2007

� Decided: 12m, alt-az mount, surface requirement to 5 GHz, cost delta for 10 GHz, interest in composite materials

xNTD Technology Parameters

• Area = 3500 m2 (30 dishes, 435 baselines)

• Tsys = 50 K

• Frequency range = 0.7 – 1.7 GHz

• Instantaneous Bandwidth = 300 MHz

• 8192 frequency channels

• Number of independent beams = at least 30

� each beam ~1 sq deg � ~ 30 sq deg FoV at 1.4 GHz

• Maximum Baseline ~ 2000 m (=> 30 arcsec beam)

• Full cross correlation of all antennas

• Located in the RQZ at Mileura, Western Australia

• Storage space for the full spectral data of 1 day

• CPU to process full spectral line and continuum data

xNTD —Some other Questions/Decisions

• Involvement of Science community (eg xNTD science workshops)

• xNTD baseline specs (previous slide)

• The “metric” for xNTD is the “survey speed”

� (Collecting area)2 x (Tsys)-2 x FOV

� Cost Model now available to consider how we best tackle possibleoptions if more funding becomes available or if we need to compromise the existing specs

� Options:

� Increase survey speed by either increasing antennas or increasing FOV

� Increase or decrease bandwidth

� Increasing the maximum baseline length

� Increase number of spectral channels

� Increase survey speed by reducing Tsys, ie by cooling the FPA elements and/or LNAs

� Expand the freq range upwards to 3 GHz, or downwards to 300 MHz

� Investment in receivers on a chip, possibly cooled

Antennas: the xNTD and SKA Perspective

Present xNTD spec calls for:

� 30 parabolic dish antennas, 12m diameter, operating to 5 GHz

� Budget AUD 300K each assembled

� Translates to ~ AUD $2600 per m2

� Like to show a presence in Mileura during 2008/2009

� 6 antennas at Mileura in 2008, thereafter N (2009/10)

Very similar requirements for South Africa KAT project

If 12 m dishes are used for SKA, the requirement is for

� ~7500 antennas for full SKA (~2013 – 2016)

� Budget AUD 100K each assembled

� Translates to AUD $765 per m2

� In Australia? (should know ~ 2008)

Is innovation required to meet cheap manufacturing challenges?

‘accepted wisdom’ has said that manufacturing dominates steel dish costs, and cost of composite material is prohibitive

Opportunities and needs

Antennas

� Ambitious cost target $300K per 12 m dish

� Lightweight, on-site kit installation, minimal special setup requirements

Smart imaging feeds – array antennas

� A critical component

� Performance and cost must be demonstrated

Receivers

� Much lower cost - $200-300 per element target

� Must use more consumer-oriented radio technology

Digital processing

� Huge processing needs

� Looks achievable within cost and performance –Moore’s law – FPGA, XCELL?

Data transport

� Terabit/sec data volumes per telescope.

� Can we use low cost CD/DVD laser technology? Low cost DWDM?

� Substantial post-correlator long haul data rates

Computing

� More complex and more important than ever before

� New strategies important to contain development costs

SoftwareSome of the Functions:

• (Configuration studies; simulations of various architectures)

• Calibration and correction of data

• Produce images

• Adaptive correction for atmospheric etc effects

• Removal of unwanted image responses

� eg, strong sources of energy elsewhere in the sky

Some of the Realities:

• We have limited resources

• ATNF can afford at most 50 person-years of effort in computing

� ALMA (Attacama Large Millimeter Array) has 430!

� KAT software team collaborating with xNTD software team

� Has enabled us to effectively use 100 person-years

• Software costs are driven by complexity

� So we must limit complexity

� Propose to limit complexity at the front end

• Only support limited range of types of observations

CSIRO Relevant Achievements— building new instruments at remote sites

•Parkes

� Designed late 1950s,completed in 1961,expected life 15 – 20 years

Parkes; 45 years later

Narrabri:Solar Heliograph built in 1964

Narrabri:Heliograph closed in 1983,ATCA built 1988

Technology to increase survey speed(multibeam receivers for Parkes & Arecibo)

New & Different Technologies

But for xNTD and SKA:

• Much cheaper antennas —

� 30 for xNTD, 7000 for SKA

• Much cheaper and smaller receivers

� 200 for each antenna =>

� 6000 for xNTD, 1 million for SKA

• Much more reliance on digital systems and software

• Substantial distances of very high-speed data transmission

• Operation in extremely remote & harsh environment

The SKA/xNTD radio camera – part 1

Beamformer

Smart feed

Correlator

and further

processing

Multiple

beams

xNTD will have ~30 beams

Each beam ~1 sq deg

Wide field of view is ~ 30 sq deg

The xNTD radio camera - part 2

30 antennas spread over 2 km contribute high angular resolution to the imaging

� Signals from each pair of telescopes are correlated (multiplied together)

� 435 separate correlations

� Final beams are formed or synthesised in software

Repeated for each telescope beam for wide field of view

� Multiple correlators – 30 times

Repeated at narrow frequency spacing to get spectral information over wide band

� Up to 40,000 frequency channels

Number of separate correlations is 435*30*40,000 = 522,000,000 every 10-60 secs

PAF requirements for the xNTD

30 beams at 1.4 GHz

Roughly 100 elements, dual polarisation

� Square or circular array depending on electrical or mechanical rotator - TBD

At least 2.5:1 bandwidth from 700 MHz

Good stability and calibration – free of strong frequency variations, resonances if possible

Good sensitivity – 70% aperture efficiency, 50 K Tsys over most of band (uncooled)

� Issues such as element-element coupling sufficiently controllable to achieve efficiency

Future upgrades for better sensitivity via cooling

5 by 1 test array

Simple connected array with transmission line feed

� SMA outputs (not matched)

Simplest structure to demonstrate important design issues

� In H-plane, pattern is sufficient to allow good efficiency – only 1 row needed F/D = 0.4 dish

� Good size for modelling

Test array suffers from “monopole” radiation

� Some efficiency loss over a range of frequencies

Intent is to validate Microwave Studio and other modelling

� May also be test bed for some trials

Use spherical near field range

� Not so accurate below 1.5 GHz

Phased array feed structure

Low cost manufacture

Modular to allow replacement of failed parts

Self-test and healing?

LNA may be separate from receivers

� LNA performance critical

� Receiver cost critical – potential integration

May ultimately need to cool LNAs to roughly 100 K (liquid Nitrogen?)

Power dissipation must be controlled – operating costs and temperature rise

Receivers – concept integrated design

xNTD initial design uses discretes – double conversion

Ultimately we will need integrated receivers on a low cost process

� Prototype RF-CMOS (IBM 0.18 µ) design completed and in fab – Suzy Jackson

� Demonstration with 300-1700 MHz, 160 MHz IF, dual 6-bit ADCs at 256 Msample/s

� Future requirements yet to be fully determined (eg. Self test, bandwidth, optical drivers, …)

Some other local work in xNTD

Receivers on chip

• Collaboration between researchers at CSIRO ATNF, La Trobe University and UNSW designing structures for trials using Peregrine CMOS process (Silicon-on-Sapphire).

• CSIRO MIMIC & LNA expertise, La Trobe & UNSW expertise in LNAs and experience with Peregrine’s design tools and fabrication process

• multi project chip test run in March 2007

• Probably also test some digital designs, eg 8-bit ADC using Peregrine and other interested parties

Advantage of Cooling LNAs

Figure of Merit for SD-FPA concept (using 12m reflector antennas)

Freq (GHz) 0.3 0.6 0.8 1.4 3 4 8 10

Aeff/Tsys goal (m^2/K) 5000 20000 20000 20000 20000 20000 20000 20000

Receiver Noise (K) uncooled 30 26 24 20 20 20 24 28

Sky Noise (K) 50 11 10 5 5 6 6 10

Antenna Noise (K) 20 12 10 10 12 15 17 17

Total Tsys (K) 100 49 44 35 37 41 47 55

Effective Area, Aeff (km^2) 0.50 0.98 0.88 0.70 0.74 0.82 0.94 1.10

Efficiency 0.60 0.60 0.65 0.80 0.70 0.60 0.65 0.60

Physical Area (km^2) 0.83 1.63 1.35 0.88 1.06 1.37 1.45 1.83

Required No. of 12m antennas 7368 14442 11971 7737 9347 12084 12787 16210

Aeff/Tsys achievable with 7737

antennas (m^2/K) 5250 10714 12926 20000 16554 12805 12101 9545

If Cooled LNAs are used:

Receiver Noise (cooled) 30 10 8 5 5 5 6 7

Antenna Noise (K) 20 12 10 6 6 6 6 6

resultant Tsys (K) 100 33 28 16 16 17 18 23

Physical Area (km^2) 0.83 1.10 0.86 0.40 0.46 0.57 0.55 0.77

Required No. of 12m antennas 7368 9726 7618 3537 4042 5010 4897 6779

Aeff/Tsys achievable with 3537

antennas (m^2/K) 2400 7273 9286 20000 17500 14118 14444 10435

COMMENTS: The above table shows the advantages of using cooled LNAs. Looking at the situation at 1.4 GHz, the number pf

antennas required is substantially reduced. However, at the frequencies where the sky noise dominates, then obviously the

advantage of cooling is diminished. It is suggested that the number of receiver channels required to achieve a given instantaneous

FOV is similar, regardless of the chosen antenna architecture. So if cooling is considered appropriate for single-feed dishes, then

why not for FPAs? It will be a major challenge to provide cooling for (typically) 200 receiver channels in a (typically) 1 sq m area. If

one cooler is shared amongst some number of receiver channels, then cooling may be possible The rows showing the achievable

Aeff/Tsys are calculated using the number of antennas required to achieve the Aeff/Tsys goal at 1.4 GHz..