RFI 2004RFI 2004

The Future of our Radio Window to the Universe

Penticton July 16, 2004Ron Ekers

CSIRO, Australia

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OverviewOverview

Why do we care?Sharing the spectrumChanging technologyNew telescopesRegulation or mitigation ?International activitiesEnvironmental credits and other social issues

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Why do we care?Why do we care?

Its our livingOur science is more important than other uses of the spectrumBecause we have expensive telescopesBecause the public like astronomySo future generations can continue to explore the universe

The The 3 Nobel prizes in 3 Nobel prizes in Radio AstronomyRadio Astronomy

Discovery of neutron stars– radio pulsations (pulsars)– Joclyn Bell & Tony Hewish

Cosmic Microwave Background (1965)– Nobel prize to Penzias and Wilson

» Bell Telephone Labs

– Technology driven serendipity

Verification of Einstein's prediction of gravitational radiation– 1993 Noble prize to Taylor and Hulse

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Sharing the spectrumSharing the spectrumSharing the technologySharing the technology

There is a communications revolution– Support not impede

Navigation (GPS)– motherhood

RFI mitigation– We can both win – but we need new paradigms

Multi-pathing advantages, spread spectrum…..Communications technology– Software radio’s– MMIC’s– Electronic beam forming

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The Telecommunications The Telecommunications RevolutionRevolution

We cannot (don't want to) impede this revolution– We can minimise its impact on passive users of the radio

spectrumImpact of deregulation– major companies now play prominent (dominant ?) role in ITU– protection of radio astronomy must be addressed as government

policyMobile communications– Cell phones– Satellite transmissions– Aircraft communications systems

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Impact of changing technology on Impact of changing technology on Radio AstronomyRadio Astronomy

Even wider bandwidths– All ready all telescopes observe outside the protected

bandsGreater sensitivityLarge arraysMultiple simultaneous observations– LOFAR, ATA

Far more complex signal processing possible– mitigation

We need a better informed radio community

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Radio Telescopes of the FutureRadio Telescopes of the FutureHEMT receivers– wide band, cheap, small and reliable– Can build low noise systems with many elements

Focal plane arrays– Field of view

Interference rejection– adaptive cancelling can work in single dishes and arrays

More computing capacity– computing power doubles every 18months (Moore’s Law)

Communicationsdevelopments

Jill Tarter bioastronomy 2002 9

MassMass--produced parabolas: produced parabolas: The Allen Telescope ArrayThe Allen Telescope Array

SETI Institute UC Berkeley100m equivalent350 x 6.1 m parabolas0.3-11 GHz (simultaneously)2.5o FOV at 1.4 GHz4 simultaneous beamsComplete 2005

!

Jill Tarter bioastronomy 2002

ATA ATA Not Your Mother’s Telescope!Not Your Mother’s Telescope!

Uses new technologies for consumer markets, “hammered” to meet needs and reduce price

MMIC LNA

WidebandFeed

Cryoinsert

0.5 – 11GHz

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Constellations of LEO’sGlobal coverageStrong signalsRapidly moving signalsMultiple simultaneous signals

ManMan--made signalsmade signalsfrom the skyfrom the sky

Globalstar

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Space junk Space junk -- GEOGEO

Space junk Space junk -- LEOLEO

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New telescopesNew telescopes

EVLA I & IIALMASKASmall number of very large telescopesEmphasis on the early universe– EoR (80-200MHz)– Redshifted HI (200-1400MHz)– Redshifted molecules, all ν > 16GHz

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RFI in an Expanding UniverseRFI in an Expanding Universe

Expanding universe redshifts the spectral lines (diagonal lines)Horizontal lines are allocations to broadcast satellites– Grey – allocated– Red - populated

CO

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The RFI ChallengeThe RFI ChallengeTo Regulate or to Mitigate?To Regulate or to Mitigate?

Sensitivity to increase (100x)Whole of radio spectrum needed for some problems– early Universe studies require “whole” spectrum to see

redshifted lines– but only to “listen”, and only from a few locations. – 2% of spectrum is reserved for Radio Astronomy

LEO telecom satellites a new threat– no place on Earth free from interference from sky

current regulations alone will not be enough

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Radio spectrum Radio spectrum management issuesmanagement issues

We are investing a lot of resources – we don’t want the sites compromisedCommercial value of the spectrumRole of ITU– Inflexible– Long time scales– Industry pressure

National regulation– Most important for all except satellite transmissions– Eg SKA hosting proposals include National regulation

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The Two Paths The Two Paths

Regulation– Essential for ultimate

sensitivity– Need to maintain links

with ITU community– Need National regulations

» Eg Radio Quiet Zones» Local exclusion zones

Mitigation– Sharing the same

spectrum– Only way to observe at

un protected frequencies– Needed to establish

credibility– Expensive

Both Paths must be pursued vigorously for Radio Astronomy to have a future

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ITU SpectrumITU SpectrumManagementManagement

In the metre and cm band <1% is allocated to radio astronomy!

Need frequency coverage for redshifted linesNeed bandwidth for continuum sensitivity

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ITU SpectrumITU SpectrumManagementManagement

In the mm band the situation is betterBut old allocations were not at best frequencyWRC-2000 proposed changes to allocations above 71GHz will be a great improvement

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Siting Radio TelescopesSiting Radio Telescopes

Choose remote sites with natural shielding– Doesn't protect against satellite interference

Establish radio quiet zones– use National government regulations– easier for fixed than mobile transmitters– Explore coordination zone construct

Far side of moon or L2 Lagrangian point– naturally occurring radio quite zones– very expensive

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Terrestrial InterferenceTerrestrial Interference

FORTÉ satellite: 131 MHz

Forte satellite: 131MHz

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Mitigation PathMitigation Path

Great Progress – eg the talks in this meetingFrom conceptual ideas to real implementationsResults usually exceeding expectationsRapid developments in techniquesSubstantial increase in understandingSlow take up in our own communityNeed to stop fouling our nest!

15 June 2004 John Reynolds - ATUC 24

Uncaged Dell P3

Box caged;CRT, KB, Mouse uncaged

Canobolas TV Cell phone

PC ShieldingPC Shielding

W. Wilson ATUC June 2004

Dynamic rangeDynamic range

• RFI at Mopra

• 0 to 256MHz

• MIT LOFAR Antenna

• 256MHz, 1024 channel polyphase digital filterbank

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RFI fundamentalsRFI fundamentals

The interference and radio astronomical signals can differ in all these parameters– Frequency– Time– Position– Polarization– Distance– Positivity

We can use one or more of these to separate the interference from the astronomical signals

In this phase space the radio sky is very empty!

- eg pulsar dispersion}Antenna arrays can cancel RFI using all

these !

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Radio Astronomy Radio Astronomy -- CommunicationsCommunicationsthe Differencesthe Differences

Radio astronomers only want the signal statistics not the signalINR/SNR > 1 (ie Interference > Signal)– this changes radio astronomy from other fields

Adaptive canceling– most people provide a reference which is most like the

desired signal– radio astronomers provide a sample of the interferer as

most like what we don’t want!

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International activitiesInternational activities

ITU (task group 1/7)IAU Com 50URSICOSPAROECD global science forumSKACollaborative RFI research

- IUCAF}

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OECD Global Science Forum OECD Global Science Forum

Task Force on Radio AstronomyMembers– Astronomers– Regulators– Satellite Communications Industry

Expanding universe requires access to the entire spectrum from a few locations rather than protection of a few frequencies at any location– ALMA, SKA

Report– http://www.oecd.org/dataoecd/54/33/280

11602.pdf

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OECD GSF Task ForceOECD GSF Task Force

Recommendations on Radio Astronomy and the Radio Spectrum

1. Establish a technical forum to improve dialog between astronomers and communications engineers

2. Governments to consider “Controlled Emission Zones” and radio astronomers to rapidly identify such locations

3. Interference in allocated bands is ITU business4. Consultation between radio astronomers and Satelite

operators to share real time operational information» Scheduling and mitigation issues

9 Jan 2002 R. Ekers 31

OECD: Some interesting issuesOECD: Some interesting issuesWe can sell value of radio astronomy to the communications industry –– Eg many common problems

Satellite operators v satellite buildersOther threats– Transmissions from aircraft– High altitude platforms (HAPs)

There are win – win situationsAccess to informationSelling the spectrumWill ITU survive?

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EconomicsEconomicsSpectrum pricing– possible incentives for careful use of the resource– NB radio astronomy cannot afford commercial rates– green tax to fund interference management and research– Environmental Credits

The cost of being Green– long term economic cost are relatively small– however up front R&D costs to an individual company may

compromise their competitive advantage – hence this issue must be addressed at national or international

policy level

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Issues for the communityIssues for the community

Whole of radio spectrum needed for redshifted lines– Only 2% of spectrum is reserved for Radio Astronomy by

regulation so we must develop other approaches

We cannot (and don't want to) impede the telecommunications revolutionRadio astronomy has low credibility until we use advanced techniquesEssential to influence government policy– astronomers should have a uniform position

Threatening language doesn’t help– is interference harmful?

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Radio Astronomy imageRadio Astronomy image

M. MorimotoCharm & Crisis in Radio AstronomyModern Radio Science 1993

Radio or optical, dark sky with beautiful view to the Universe is the precious treasure of the Nature.

It is only the human wisdom needed to protect the Nature