The Square Kilometre Array: An Engineering Perspective

408 Pages·2005·6.4 MB·English

by  Peter J. Hall

THE SQUARE KILOMETRE ARRAY:
AN ENGINEERING PERSPECTIVE
Editedby:
PETERJ.HALL
InternationalSKAProjectOffice,
Dwingeloo,TheNetherlands
ReprintedfromExperimentalAstronomy
Volume17,Nos.1–3,2004
LibraryofCongressCataloging-in-PublicationDataisavailable
ISBN1-4020-3797-x
1-4020-3798-8
Published bySpringer,
P.O.Box17,3300AADordrecht,TheNetherlands.
TheselectionofanSKAsiterequirescomprehensivecharacterizationofthe
radio-frequencyenvironmentatcandidatelocations.WhiletheSKAwillfeature
advancedradio-frequencyinterference(RFI)mitigation,thesciencegoalsalso
demandaradio-quietsetting.Aspartofaninternationalengineering
collaboration,aspecialistteamfromTheNetherlandsFoundationforResearchin
Astronomy(ASTRON)isworkingwithlocalengineersinArgentina,Australia,
ChinaandSouthAfricatoinvestigatecandidatesites.Thepictureonthecover
showsthefacilityestablishedbyASTRONandSouthAfricanengineersatthe
remoteK3candidatesite,intheKaroowildernessofSouthAfrica.Similarcamps
willbeset-upformeasurementsintheothercountriesduring2005.Photocredit:
RobMillenaar,ASTRON
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(cid:1)c Springer2005
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utilizedinanyformorbyanymeans,electronicormechanical,
includingphotocopying,recordingorbyanyinformationstorage and
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PrintedintheNetherlands
TABLEOFCONTENTS
RichardSchilizzi/Foreword 1
PeterHall/Introduction 3
P.J. Hall / The Square Kilometre Array: An International Engineering
Perspective 5–16
SKADEMONSTRATORSANDRESULTS
David Deboer, Rob Ackermann, Leo Blitz, Douglas Bock, Geoffrey
Bower, Michael Davis, John Dreher, Greg Engargiola, Matt Fleming,
Girmay-Keleta, Gerry Harp, John Lugten, Jill Tarter, Doug Thornton,
Niklas Wadefalk, Sander Weinreb and William J. Welch / The Allen
TelescopeArray 19–34
Stefan J. Wijnholds, Jaap D. Bregman and Albert-Jan Boonstra / Sky
Noise Limited Snapshot Imaging in the Presence of RFI with LOFAR’s
InitialTestStation 35–42
Kjeld van der Schaaf, Chris Broekema, Ger Van Diepen and Ellen van
Meijeren/TheLOFARCentralProcessingFacilityArchitecture 43–58
StefanJ.Wijnholds,A.gerdeBruyn,JaapD.BregmanandJan-Geralt
bijdeVaate/HemisphericImagingofGalacticNeutralHydrogenwitha
PhasedArrayAntennaSystem 59–64
A.vanArdenne,P.N.Wilkinson,P.D.PatelandJ.G.bijdeVaate/Elec-
tronicMulti-BeamRadioAstronomyConcept:EmbraceaDemonstrator
fortheEuropeanSKAProgram 65–77
Ray Norris / The Australian SKA New Technology Demonstrator
Program 79–85
ANTENNAS
E.E.M. Woestenburg and J.C. Kuenen / Low Noise Performance
PerspectivesofWidebandAperturePhasedArrays 89–99
W.A. van Cappellen, J.D. Bregman and M.J. Arts / Effective Sensitivity
ofaNon-UniformPhasedArrayofShortDipoles 101–109
Germa´n Corte´s-Medell´ın / Low Frequency End Performance of a
Symmetrical Configuration Antenna for the Square Kilometre Array
(SKA) 111–118
RogerSchultz/RadioAstronomyAntennasbytheThousands 119–139
John S. Kot, Richard Donelson, Nasiha Nikolic, Doug Hayman, Mike
O’SheaandGaryPeeters/ASphericalLensfortheSKA 141–148
MariannaV.Ivashina,JanSimonsandJanGeraltbijdeVaate/Efficiency
AnalysisofFocalPlaneArraysinDeepDishes 149–162
Meyer Nahon, Casey Lambert, Dean Chalmers and Wen Bo / Model
ValidationandPerformanceEvaluationfortheMulti-TetheredAerostat
SubsystemoftheLargeAdaptiveReflector 163–175
Wenbai Zhu, Rendong Nan and Gexue Ren / Modeling of a Feed
SupportSystemforFast 177-184
JohnD.Bunton/CylindricalReflectors 185–189
RFSYSTEMS
J. Bardin, S. Weinreb and D. Bagri / Local Oscillator Distribution Using
aGeostationarySatellite 193-199
SuzyA.Jackson/RFDesignofaWidebandCMOSIntegratedReceiver
forPhasedArrayApplications 201–210
DATATRANSPORT
D.H.P. Maat and G.W. Kant / Fiber Optic Network Technology for
DistributedLongBaselineRadioTelescopes 213–220
Ralph Spencer, Roshene McCool, Bryan Anderson, Dave Brown and
Mike Bentley / ALMA and e-MERLIN Data Transmission Systems:
LessonsforSKA 221–228
SIGNALPROCESSING
Alle-Jan van der Veen, Amir Leshem and Albert-Jan Boonstra / Array
SignalProcessingforRadioAstronomy 231–249
JohnD.Bunton/SKACorrelatorAdvances 251-259
StevenW.Ellingson/RFIMitigationandtheSKA 261–267
R.H. Ferris and S.J. Saunders / A 256 MHz Bandwidth Baseband
Receiver/Spectrometer 269–277
TimothyJ.Adams,JohnD.BuntonandMichaelJ.Kesteven/TheSquare
KilometreArrayMolongloPrototype(SKAMP)Correlator 279–285
Kjeld van der Schaaf and Ruud Overeem / COTS Correlator
Platform 287–297
John D. Bunton and Robert Navarro / DSN Deep-Space Array-Based
NetworkBeamformer 299-305
DATAPROCESSINGANDSOFTWARE
T.J. Cornwell and B.E. Glendenning / Software Development for the
SquareKilometreArray 309–315
A.J. Kemball and T.J. Cornwell / A Simple Model of Software Costs for
theSquareKilometreArray 317–327
T.J. Cornwell / SKA and EVLA Computing Costs for Wide Field
Imaging 329–343
Colin J. Lonsdale, Sheperd S. Doeleman and Divya Oberoi / Efficient
ImagingStrategiesforNext-GenerationRadioArrays 345–362
SYSTEMISSUESANDMISCELLANEOUS
Jaap D. Bregman / System Optimisation of Multi-Beam Aperture
SynthesisArraysforSurveyPerformance 365–380
JohnD.BuntonandStuartG.Hay/SKACostModelforWideField-of-
ViewOptions 381–405
Jaap D. Bregman / Cost Effective Frequency Ranges for Multi-Beam
Dishes,Cylinders,ApertureArrays,andHybrids 407–416
JohnD.BuntonandT.JosephW.Lazio/Cylinder–SmallDishHybrid
fortheSKA 417–422
B.Peng,J.M.Sun,H.Y.Zhang,T.Y.Piao,J.Q.Li,L.Lei,T.Luo,D.H.Li,
Y.J.ZhengandR.Nan/RFITestObservationsataCandidateSKASite
inChina 423–430
ExperimentalAstronomy(2004)17:1
FOREWORD
TheSquareKilometreArray(SKA)Projectisaglobalprojecttodesignandcon-
struct a revolutionary new radio telescope with of order 1 million square meters
of collecting area in the wavelength range from 3 m to 1 cm. It will have two or-
dersofmagnitudegreatersensitivitythancurrenttelescopesandanunprecedented
largeinstantaneousfield-of-view.ThesecapabilitieswillensuretheSKAwillplay
a leading role in solving the major astrophysical and cosmological questions of
theday(seethesciencecaseatwww.skatelescope.org/pages/page astronom.htm).
TheSKAwillcomplementmajorground-andspace-basedastronomicalfacilities
underconstructionorplannedinotherpartsoftheelectromagneticspectrum(e.g.
ALMA,JWST,ELT,XEUS,...).
ThecurrentschedulefortheSKAforeseesadecisionontheSKAsitein2006,a
decisiononthedesignconceptin2009,constructionofthefirstphase(international
pathfinder)from2010to2013,andconstructionofthefullarrayfrom2014to2020.
Thecostisestimatedtobeabout1000M .
TheSKAProjectcurrentlyinvolves45institutesin17countries,manyofwhich
areinvolvedinnationally-orregionally-fundedstate-of-the-arttechnicaldevelop-
ments being pursued ahead of the 2009 selection of design concept. This Special
Issue of Experimental Astronomy provides a snapshot of SKA engineering activ-
ity around the world, and is based on presentations made at the SKA meeting in
Penticton,BC,CanadainJuly2004.Topicscoveredincludeantennaconcepts,soft-
ware,signaltransportandprocessing,radiofrequencyinterferencemitigation,and
reportsonrelatedtechnologiesinotherradiotelescopesnowunderconstruction.
Furtherinformationontheprojectcanbefoundatwww.skatelescope.org.
RICHARDSCHILIZZI
InternationalSKAProjectDirector
ExperimentalAstronomy(2004)17:3
INTRODUCTION
ThisSKAspecialissueofExperimentalAstronomyisasnapshotofkeyengineer-
ingactivities,rangingfromantennaprototypingtosoftwaredesign.Theemphasis
which the SKA community places on prototyping and demonstration is apparent
fromthemixofincludedpapers.Excellentearlyresultsfromlargeendeavourssuch
astheAllenTelescopeArrayandLOFARunderlinethevalueofthisemphasisbut
therearemanyadditionalencouragingreportsfromotherprojects.Mostdealwith
crucial sub-systems and components, common to all SKA concepts. A series of
whitepapersoverrecentyearshasilluminatedimportantSKAdesignissuesand,in
thistradition,afeatureofthisvolumeistheinclusionofthefirstsubstantialpapers
dealingwithSKAdataprocessingandsoftware.
IhopethatyouenjoythissummaryofSKAengineeringandrelatedactivities,
andIthankauthors,reviewersandExperimentalAstronomystafffortheirassistance
in producing the volume. As Richard Schilizzi mentions in his Foreword, more
informationabouttheSKAisavailableatwww.skatelescope.org.Readersinterested
in additional aspects of the project engineering, including costing exercises and
industrialliaison,willfindagrowinglistofmaterialonthewebsite.
PETERHALL
InternationalSKAProjectEngineerandGuestEditor
ExperimentalAstronomy(2004)17:5–16 (cid:1)C Springer2005
THE SQUARE KILOMETRE ARRAY: AN INTERNATIONAL
ENGINEERING PERSPECTIVE
P.J.HALL
InternationalSKAProjectOffice,P.O.Box2,7990AADwingeloo,TheNetherlands
(E-mail:[email protected])
(Received2August2004;accepted4October2004)
Abstract.ThepaceoftheinternationalSquareKilometreArray(SKA)projectisaccelerating,with
majorconceptreviewsrecentlycompletedandanumberoftechnologydemonstratorswellunderway.
First-roundsubmissionstohostthetelescopewerelodgedbysixcountries.TheSKAtimelinecurrently
showsasitedecisionin2006,andoneormoretechnologyconceptschosenin2008.Thetelescope
isexpectedtobeoperational,invariousphases,intheperiod2015–2020.Thispapergivesastatus
reviewoftheproject,andoutlinesengineeringconceptdevelopmentanddemonstrationprojects.
Keywords: aperture synthesis, interferometry, international science projects, next-generation tele-
scopes,novelantennas,radiotelescopes
1. Introduction
TheSKAradiotelescopeprojectisaninternationalendeavourtobuildanaperture
synthesis radio telescope with one million square metres of effective collecting
area, operating the range 100 MHz to 25 GHz (Schilizzi, 2004). A major target
of the project is to achieve a sensitivity gain of 100 relative to present-day radio
interferometers.Thisisexpressedinakeyspecification(Jones,2004):overawide
frequency range the sensitivity metric, A /T , should be of order 20000. Here,
eff sys
A is the effective collecting area (m2) and T is the system equivalent noise
eff sys
temperature(kelvin).Withacanonical50Ksystemtemperature,therequiredA
eff
is106m2,or1km2.Whilehalfthecollectingareawillbelocatedinacentralregion
of ∼5 km diameter, the full array will extend across trans-continental distances
(Figure1).
TheSKAprojectrosetoprominenceinthelate1990swiththeformationofthe
International SKA Steering Committee, an overseeing body currently consisting
of representatives from 17 countries. The estimated construction budget is USD
1B (year 2004 dollars), a figure demanding many new technology developments
in order to yield a cost per unit collecting area of one-tenth that of existing radio
telescopes.AnInternationalSKAProjectOffice(ISPO)isnowfunctionalandthe
firstInternationalDirectorandProjectEngineercommencedappointmentsin2003
and2004,respectively.
6 P.J.HALL
Figure1. ExampleofapossibleSKAconfiguration.Inthismodel,patchesofcollectingarea(stations)
extendfromadensecoreinalog-spiralarrangement.Thepatterncontinuestobaselinesof∼3000
km,withabout10%ofthetotalcollectingareabeingoutsidethescaledepicted.
A recent series of whitepapers (ISPO Concept Whitepapers, 2003), or end-to-
end descriptions of potential SKA designs, have proved invaluable in promoting
science and engineering discussion, identifying areas in which there are deficien-
ciesinknowledgeorspecificationclarity,andstimulatingnewstudies–including
simulationofperformanceandcosttradeoffs.Ineffect,thewhitepapersareslices
throughacomplexproblemandsolutionspace,thesamplesolutionsbeingusedto
illuminate critical issues and provoke still more imaginative designs. An updated
sciencecasefortheSKA(CarilliandRawlings,2004)identifiesfivekeyareasof
astronomy and cosmology, with the original driver – the evolution of structure in
theprimordialUniverse–stillfiguringprominently.
Aswellasthemanytechnologydevelopmentprojectsunderway,animportant
additionalaspectofSKAengineeringdealswithsiteinfrastructuredesignandcost-
ing.InitialsitingproposalswerereceivedfromArgentina,Australia,Brazil,China,
South Africa and the USA (ISPO Site Whitepapers, 2003). A first costing study
(Hall, 2003a) puts the infrastructure value of the project at around USD 250M,
including a custom optical fibre communications network for at least the central
array. Regardless of the site chosen there will be significant infrastructure chal-
lengesinareassuchasremotepowerprovision,activeandpassiveenvironmental
conditioning,andlow-costaccessroadconstruction.
AdecisiononSKAsitingisscheduledfor2006,withprecedingmeasurements
of radio-frequency (RF) interference at candidate locations being made both by
site proponents and the ISPO, the latter via a contract with ASTRON, the Dutch
nationalradioastronomyorganization.Thesetechnicaleffortsprovideasnapshot
of the current RF environments and a parallel part of the site proposal process
involves proponents examining the feasibility of establishing a radio-quiet zone
forthecentralpartoftheSKA;suchazonewouldprovidelong-terminterference