wide-field radio astronomy – a historical perspective · new ideas and new r.a. achievements; a...

Arnold van Ardenne ([email protected])With contributions from Jan Geralt bij de Vaate, Jess Broderick, Albert-Jan Boonstra a.o.

Wide-field Radio Astronomy –a historical perspective

Towards an All-Sky Radio SETI Telescope, JBO-UMan1018

Golden Record Voyager 1977See e.g. Mike Garrett inWesterbork 50yrs Book

WideWide-Wide-field Radio field Radio AstronomyOutline

• Introduction, scene setting

• Some (personal) notes on History

• Widefielding concepts

• Developments

• SETI Scenario/Oiutstanding Issues?

• Summary

New Ideas and new R.A. achievements; a two-way street

• New Technologies and New Instruments enable new horizons in Radio Astronomy andSETI

• Synergies: Science, Technology, Industries, Users, Society & Education


Society &

“General Tendencies do not alone decide; great personalities are always necessary to make them effective”Leopold von Ranke (Historical writer 1795-1886)

New Ideas and new R.A. achievements; a two-way street

• New Technologies and New Instruments enable new horizons in Radio Astronomy andSETI

• Synergies: Science, Technology, Industries, Users, Society & Education

• New Observing and Paradigm shifts:o Sensitivity, Frequency bandwidth (span)o Ultra Deep polarimetric imagingo Connectivity, flexibilityo Field of view, Time varying Universeo Multi- vs. Single sky pixel processing o (HPC) Computing & Massive Data o View on “low power”?

• All relevant to All-Sky Radio SETI !?


Society &

“General Tendencies do not alone decide; great personalities are always necessary to make them effective”Leopold von Ranke (Historical writer 1795-1886)

Key Improvement areas in 70 yrs R.A.

Facts and Figures Enabling key technologies

Sensitivity ~105x in 70 years(SKA: 50-> 100x?)

Collecting Area, Receivers and SW

Angular resolution ~107x in 70 years Baseline extension (“VLBI”), clocks and network-

technologies

Field of View(all resolution pixels)

>~105x in 70 yearsSKA: 100-104x

(computing power measure using AA’s)

Array techniques, SW and Computing power

Peta (symbol: P) is 1015, LOFARExa (symbol: E) is 1018 SKA

Time resolution Seconds to nsec SW and Computing power

• A Telescope must be pointed in the a specific direction

• A Telescope must have precisely made parts

• A Telescope must have moving parts

• A Telescope can be used by only one person at a time

Project ARGUS: • All-seeing timed antenna array• Thousands to millions of integrated elements and computers • Overthrows Galilean legacy

Roughly fitted ideas in first early SKA R&D program in ASTRON @ 1st “SKA” WS Delft 1996

“Legacy of Galileo”(Robert S. Dixon, OSU when presenting Project ARGUS @ 1st “SKA” WS Delft 1996)


System overview Sydney/ATNF 1997 (following on from 1st “SKA” WS in Delft 1996)

Some History

08/07/01AvABerkSKAYworkshop

(1) Different Noise regimes stimulate different approaches

0.01 0.1 1.0 10. 100. 1000.

Frequency in GHz

1.

10.

100

.

1000

.

Tem

pera

ture

in

K

LOFAR

SKA(mid)

ATA -like

Some History

Ref.: SKA-workshop-Berkeley-08-07-01/AvA


Ref. SKA-Symp-Dwingeloo-12-04-99/AvA

(2) R.A. Technology does not allow otherwise over, say, 3 decades freq. BW.


Approximate frequency ranges of activities on main (SKA) concepts

10 GHz

LOFAR

.01 0.10 1.0

1hT (ATA from 2001)

M-SKA/ Electr.Adapt.Array/Lü-neburg lens

Indian steel wire Reflector

LAR(Can.)

Large Sp. Refl./FAST

Telescope (concepts)

Ionospheric cut-off

Aperture Arrays

Paraboloids

Pursued for SKA (mainly Europe):

Some History


(08/07/01AvABerkely-SKA-workshop)

Economics; (Estimated) Cost and number of elements versus Time

AAD

103

102

10

104

105

106

OSMA

97 98 01200099 02 03 04 2005 06

Pre-study and Early prototyping (proving concept)

Number ofelements

AAD (1 beam)

Cost (Euro)per Sq. meter

OSMA (2+2 beams)

THEA (2x4 beams)

Note:CostSlopes per beam much steeper!

07 0908

main results:•Trx & Cost reduced •SKA freq, range 0.5-1.7GHz•Larger Freq. BW •Outdoor system tests; “real” test sources and results•Improved design with multi (8) digital beams, 2 FOV’s • Adaptive beamforming (analog & dig.)

LOFAR-like early R&D, Preps Lofar-like Development and roll out

Some History (Early R&D @ ASTRON)

SKADS preps

Early contr.: Felix Smits, Michel Arts, Grant Hampson, Bart Smolders, Gie Han Tan, Andre Kokkeler, Christophe Craye, Jan Geralt bij de Vaate, Marianne Ivashina,Rob Maaskant, Stefan Wijnholds, Jaap Bregman (ASTRON), Dan Schaubert (Univ.Mass.), Zoya Popovic (Univ.Colorado) and other collaborators


SKA; two basic antenna conceptsImaging and multibeaming in (almost) entire half sphere

Imaging and multibeamingwithin reflector FOV

Element antenna patternS.E.Reflector pattern

Digital beams

No widely spaced beam

possible

Some History


(08/07/01AvABerkely-SKA-workshop)


Sensitivities over Three decades SKA freq. range in 3 concept technologies

10 GHz.10 1.0

Aeff/Tsys(m2/K)

104

103

Act.dipolearray

Many Smallparaboloids

Electr. Adapt.Array

105

LOFAR

Techn. Conc. Aeff(m2 @ f GHz) Trx (K) η

Active Array 107 , 0.1 <Tsky 1Electr. Adapt. 2.106 , 1.0 80 0.8Multi Parabol. 2.105 , all 25 0.65

ATA-like

Some History


08/07/01AvABerkely-SKA-workshop

Three decades freq. range in 3 concept technologies

10 GHz.10 1.0

Aeff/Tsys(m2/K)

104

103

Act.dipolearray

Many Smallparaboloids

Electr. Adapt.Array

105

e.g. LOFAR

Techn. Conc. Aeff(m2 @ f GHz) Trx (K) η

Active Array 107 , 0.1 <Tsky ~1Electr. Adapt. 2.106 , 1.0 <40 0.8Multi Parabol. 2.105 , all 25 0.65

ATA

History updated, some 10+ years later

dense


Note1: From 2000 resolved “Dense” vs. “Sparse” array behaviourNote 2: SKADS EC-FP6 study resulted in SKA system scenario and notably Embrace (WSRT, Nancay) and 2-PAD (JBO)emphasizing Wide Field AA S&T.

(USA)

42x6m hydroformeddishes

Approximate frequency ranges for SKA and new single pixel reflectors

10 GHz

LOFAR, LWA, MWA, SKA-Low

.01 0.10 1.0

ATA(from 2001)

(M-SKA/ Electr.Adapt.Array/Lü-neburg lens)

Large Sp. Refl./FAST*

Telescopes

Ionospheric cut-off

Aperture Arrays

Paraboloids

for SKA:

History Updated, today

SKA-Mid, MeerKat


* Multibeam

LOFAR and SKA synergies

antennacluster

signalprocessingcenter

350 km

•Configuration & Calibration studies• High capacity scalable Optical networking (up to 20 Tb/sec)

• Massive Parallel processing central facility• Algorithm developments and RFI studies• Fully integrated wide frequency band Frontends

Relatively simple Active wide band antenna <10- 90 MHz, 110-250MHz

Antenna technology is separate RDD line

Technologically advanced antennas for which R&D and industrialization steps are required; focal plane arrays* may help as intermediate steps

2000 20152005 2010

(08/07/01AvABerkeley-SKA-workshop)Back to Some History


* FPA now PAF; Phased Array FeedNew name through Peter Hall 2005

2000 20152005 2010

Phased Array Feed Developments for Reflectors in time (and very brief)

Faraday/Radionet FP52001-2004,2-5GHz,JBO, ASTRON, IRA, CSIRO,Torun

AvA, Peter Wilkinson, Jan Geralt bij de Vaate,

Peter Hall

Pharos/Radionet FP62004-2007,Cooled System,HTc, 4-8GHzJBO/UMan, ASTRON, IRA, Mecsa,CSIRO,Torun,UBirmingham

NFRA Note 430, 1983, AvA NFRA Note 513, 1987, AvA

Investigated multibeamarrays in the early 80-ties for (sub)mm astronomy; no e.m. solution to overcome non-beam overlap at that time.

Had to wait another 15+ years!

Progress report Univ. Mass.Dan Schaubert (mid 2000) collaborating with ASTRON. Dense array understood;continuous sampling nowpossible allowing for PAF’s!

Others: ASTRON (Digestif/Apertif, WSRT),DRAO (PHAD),CSIRO/CASA (Checkerboard, ASKAP),NRAO, BYU, ...

SKADS/ FP6 2005-2010,All relevant issues for AA’s 450fte, 28 institutes incl. Canada, S.A., Australia,RR(www.skads-eu.org)

SKADS prepsPeter Wilkinson, AvA

Parbhu Patel, JanGeralt bij de VaateTowards an All-Sky Radio SETI Telescope, JBO-UMan1018

PAF Compound beams demonstratedPAF Compound beams demonstratedWeights

PAF Compound beams demonstrated2D pattern

• Source: Cassiopeia A•

Source: Cassiopeia A1420 MHz

• Every pixel is from a compound beam in the Every pixel is from a compound beam in the desired direction

• Demonstrated 9 degDemonstrated 9 deg22 fieldfield-field-ofofof-of-view•

Demonstrated 9 degWSRT 0.3 Demonstrated 9 degDemonstrated 9 degWSRT 0.3 WSRT 0.3 degdegdeg2

• Courtesy Courtesy WimWim van van CappellenCappellen et.al.2012

+

+

compound beam

compound beam

No baselines ripples andhigh efficiency (2009)


LOFAR like

CONCEPTS

Ionospheric cut-off

ATA, Meerkat etc.

PAF

Reflectors/SPF

Apertif, ASKAP

Projects/Types

REFLECTORS

Fields of View

Single Mech. Pointing;Multiple E-FOV /Single beam

Single Mech. Pointing;Single FOV/Single beam

“All Sky” FOV Multiple FOV /Multiple beams

Phased Array Feeds* & Arrays in new interferometers; Frequency ranges

APERTURE ARRAYS

Note:PAFs processing:• M beams, N array elements processing÷ order of MN for N elements •T telescopes; correlation ÷ TxT (1 beam)For an AA, on a regular grid:• FFT: Mlog2N. •T stations; correlation ÷ TxT (1 beam)More, see: IEEE-Comp.Sept.2014, p.48-54, Jongerius et.al.

10 GHz.01 0.10 1.0

Sparse/ Dense

* See: History view Ekers, O’Sullivan, PAF WS, Sydney 2017 Towards an All-Sky Radio SETI Telescope, JBO-UMan1018

Dense(MFAA)

Widefield Arrays: Focal plane Arrays and AA’s

• PAF’s: Update and extension of existing and for new cm/dm telescopes

• Sweet spot PAF at higher frequencies using low cost prime focus reflector telescopes because widefield alternatives are lacking at cm/mm wavelengths

• Context: Feasable and “Natural” developments for Multipixel/Widefielding radioastronomy now, may be perceived to follow “similar” developments in optical/IR but:

• R.A. can do better; Lower frequencies to use aperture arrays sparse/dense for all-sky observing


Wilfred Frieswijk, Jason Hessels & Vlad Kondratiev, Jan.2014;Effect of ionosphere on compound beam

Example: LOFAR’s wide Field-of-View

Example Example WidefieldWidefield/Widefield/MultibeamMultibeam radio astronomy


What can What can WidefieldWidefield/All sky for example do

All-Sky• LOFAR (similarly others e.g. MWA)

• EMBRACE (no others)

Tom Hassall and the LOFAR Pulsar Working Group, Dec.2010

Courtesy: SKADS-EMBRACE (0.5-1.7GHz), Dion Kant et.al., 2012

Jason Hessels, the LOFAR Pulsar Working Group, July 2010

A Lüneburg Lens for the SKA*, an early concept*: Graeme James , Andrew Parfitt, John Kott, Peter Hall, ATNF/CSIRO, 1999

Artist impression of multitude of 5m diameter

Artist impression , flyover of 16m diameter with rotatable feed ams

With supporting reflecting goundplane

Focussing Principle

AvACSIROMT220403

Lüneburg Lens and Array measurements* @ 2.3 & 5 GHz*: Li Li, , Andrew Hunt, Geoff James e.o, ATNF/CSIRO 2003


Not downselected for SKA, but:New use in self driving cars!See e.g. https://lunewave.com/

SETI: First Ideas on many telescopes • SETI: Following OZMA (1960/Frank Drake 26m NRAO) ; Project Cyclops (1971, Bernard

Oliver/VP-HP) “the most advanced interstellar receiving system never built”.

• ARGUS: All-sky survey using (timed) phased array withAstronomy and SETI

• Early Developments for SETI (strategy 2020) and the SKA: Small “D” large “N” concept taking a step toward dedicated system

development i.e. beyond cheap satellite TVRO dishes

• Early costing by SETI, others (Sandy Weinreb, Gie Han Tan, Peter Friedman,..); balancingcost per dish, cost # Rx’s , Infrastructure vs #, Processing power, etc.

• Resulting in ATA (now 42) and efforts to 350 (Jill’s talk)

• Important and thorough concept exercise for next projects (e.g. SKA)

OZMA: Phased array of smaller antennas

Small D, Large N telescopes • Issue: Only way to reduce cost (say, per sqm) is to develop mass produced dish(elements)

• So far for even the newest dishes (apart from ATA) costs are well over 5000€/sqm; no goodstart for All-Sky SETI

• Aim should be significantly cheaper, say, <2000€/sqm (structure plus foundations)

• Only possible with prime focus 1-10/20GHz, light structures using clever (new) materialswith D=10-15mExamples

DRAO’s composite dish approach for SKA resulted in actual dish. Next steps?

ASTRON/OSO-Chalmers/ICRAR paper studies proposed thermoplastic composite dish for SKA (rms <1mm, 15m dish, projected 1st guess <2000sqm) incl. antenna perf.(M.V. Ivashina et.al. 2011, W.C. Liao et.al., EUCAP, 2012)

Note: Both relied on structural approaches from aerospace industries e.g. Airborne Composites/Nl.

WideWide-Wide-field Radio Astronomy & RFI

• Time varying universe and Widefield Radio Astronomy can be imagedusing new instruments to significantly increase discovery space:


Shimwell et al. (2017)

* Radio continuum survey revolution wellunder way at low frequencies with (very)wide FoV aperture arrays. Survey speedimprovement (∝ FoV) transformational; new parameter space being explored.

* WSRT/Apertif and ASKAP/EMU surveyswill soon similarly open up new discoveryspace at ~1.4 GHz.

* Moving towards the ultimate goal of abillion galaxy survey with the full SKA;wide FoV crucial for survey speed!

Norris et al. (2015)

Keane et al. (2015)

•HI–Billion galaxy survey out to z~2.–Cosmology (e.g. BAO); intensity mapping.–HI absorption spectroscopy. –Galactic HI, ISM in nearby galaxies,–cosmic web. –21-cm relatively weak; wide FoV often essential for survey speed!

•Pulsars–Pulsar surveys; finding up to ~40000–pulsars in the Galaxy with the full SKA.–Find the rarest objects (e.g. 'holy–grail' PSR-BH binaries) for novel–strong-field tests of GR.–Efficient bulk timing needed (e.g. for–PTA candidates for GW science).

Santos et al. (2015)

M31;Braun et al. (2009)

Tan et al. (2018) – LOFAR Tied-Array All-Sky Survey (LOTAAS)

Allison et al. (2015) - ASKAP

Example recent discoveries made with wide FoV radio telescopes....

Other current and future surveys

WideWide-Wide-field Radio Astronomy & RFI

• Time varying universe and Widefield Radio Astronomy can be imagedusing new instruments to significantly increase discovery space

• Optimum and for SETI “trustworthy”; accesible thanks to new instrumental developments incorporating RFI mitigation “by design”

• Body of Knowledge is now huge e.g. new algorithms at high speed may include Machine Learning and A.I.

• Real time algorithms fit data pipelines before and after correlation; See e.g. R. van Nieuwpoort et.al, Real Time RFI mitigation for LOFAR, Apertif and

SKA, URSI AT-RASC 2018

• Other example use multibeam aspect: Towards an All-Sky Radio SETI Telescope, JBO-UMan1018

Submitter: Jason HesselsDescription: In the ongoing LOTAAS survey, PhD student Chia Min Tan (University of Manchester) has

discovered a radio pulsar that takes 23.5 seconds to make a single turn. Compared to other known radio pulsars, which spin on average once very 0.5 seconds, this is remarkably slow and came as a big surprise to the survey team.

Interestingly, the super-slow pulsar still has a high magnetic field at its surface: roughly thirty trillion times higher than the Earth's magnetic field. This helps us understand why it is still producing visible radio pulsations, but the pulsar is ultimately an oddball and presents an important observational insight for constraining theory. It also remains a puzzle how this pulsar fits into the "zoo" of observed neutron stars. For example, is it an old descendant of the super-magnetised neutron stars known as "magnetars"? X-ray observations led by Chia Min Tan and Paolo Esposito aim to clarify this.

The pulsar was also easily detected in the LoTSS imaging survey (work done by Tim Shimwell and Cees Bassa), and underlines the promise of using that survey to find more oddball pulsars that can lead to new insights. Finding such a slowly rotating pulsar is tricky business, but showcases LOFAR's strengths: the low frequencies, high sensitivity, and multiple beams of the LOTAAS survey make it possible to differentiate the pulsar signal from human-made interference.

We are hoping that this is the tip of the iceberg for LOFAR, and that LOTAAS will reveal even slower-spinning pulsars. To that end, we've started reprocessing the archived data using algorithms better suited to finding such signals.

This artist's conception, made by Danielle Futselaar, show's the regular pulses detected in LOFAR beam-formed data (in blue), as well as the LoTSS survey detection of the point source (in red).

Copyright: ASTRON / Artwork by: Danielle Futselaar

It's good to take it slow (AJDI 23092018)


Conceptual perspective of technologies; Approximate frequency ranges

20 GHz

SETI-MFAA, 0.5-2GHz)

.02 0.20 2.0Ionospheric cut-off

Aperture Arrays

Paraboloids with PAF’s

for SETI

A view on ALL-Sky radio SETI

SETI -High, 2 bands (2-6, 6-18GHz)

SETI-LFAA, 0.1-0.5GHz)


Summary • Over the last 25 yrs Widefield All-Sky technologies exist and are well developed at

cm and longer wavelengths

• Higher frequency PAF’s seem useful for SETI but then:

• Low cost (mass produced) dishes from, say, 1-20+ GHz deserve more attention

• RFI mitigation techniques have much advanced and possibly useful approaches for SETI in e.g. “signature” analysis

• Not mentioned in talk: (i) Signal processing, HPC and data pipelines for present telescopes are state-of-the-art (ii) Power issues/operating costs are not well taking into account in design/development space.

wide-field radio astronomy – a historical perspective · new ideas and new r.a. achievements; a...

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