TheThe AllenAllen TelescopeTelescope ArrayArray
SplittingSplitting thethe ApertureAperture
David DeBoer LBNL Colloquium ATA Project Manager October 19, 2005 SETI Institute TheThe AllenAllen TelescopeTelescope ArrayArray RAL SETI Institute Leo Blitz Rob Ackermann Douglas Bock Other Larry D’Addario Geoff Bower Ed Ackermann John Andersen Mike Davis Calvin Chang Charlie Cox Matt Dexter Dave DeBoer Niklas Wadefalk John Dreher Greg Engargiola Sandy Weinreb Gerry Harp Ed Fields Matt Fleming Girmay-Keleta Colby Kraybill Jill Tarter Dave McMahon Doug Thornton Lynn Urry Jack Welch Mel Wright OutlineOutline ofof TalkTalk
•• AnAn AgeAge--OldOld QuestionQuestion •• RadioRadio AstronomyAstronomy •• SplittingSplitting thethe ApertureAperture •• TheThe ATAATA ProjectProject •• SelectedSelected InstrumentationInstrumentation AnAn AgeAge--OldOld QuestionQuestion AnAn AgeAge--OldOld QuestionQuestion
• Epicurus - “there are infinite worlds both like and unlike this world of ours” (ca 300 BC) • Lucretius - “it is in the highest degree unlikely that this earth and sky is the only one to have been created” (ca 70 BC) • The Pythagoreans pictured spectacular lunar creatures who did not defecate (!?)
However … an age-old question
• Plato – “there is and ever will be one only- begotten and created heaven” (ca 400 BC) • Aristotle rejected multiple worlds via a complex metaphysical argument (ca 350 BC)
And we know who won!
z The early church later opposed the concept of multiple worlds an age-old question
• Early thinkers had no physical framework with which to approach the problem, only philosophical and theological musings z Middle-ages (ca 1300) resurgence of “multiple worlds” and the tools to start thinking about it somewhat critically.
AreAre wewe alone?alone? EarlyEarly SETISETI ((SSignallingignalling ETIETI))
• Karl Friedrich Gauss (ca 1800)
Large right triangle in Siberia – “Hello, we trees are here”
wheat early S(ignalling)ETI
• Charles Gros advocated France building a gigantic mirror to signal Mars
• Joseph von Littrow advocated digging a large trench in the Sahara in some geometrical form, filling it with kerosene and igniting it EarlyEarly SETISETI ((SSearchearch forfor ETIETI))
• No less than Nicola Tesla and Gugliemo Marconi thought they had detected signals from another planet. EarlyEarly RadioRadio AstronomyAstronomy • Karl Jansky at Bell Labs (1933) RadioRadio AstronomyAstronomy andand WhyWhy
• Many different physical phenomenon govern how the universe works – different frequencies probe different processes • Regions are obscured at some wavelengths and not others – dust at optical not much of an issue in radio RadioRadio AstronomyAstronomy
•Thermal •Non-thermal • Spectral line CrabCrab FirstFirst DishDish
SingleSingle DishDish Single Dish
R.D. Ekers Single Dish + Focal Plane Receivers
R.D. Ekers Dish of Panels
R.D. Ekers Dish of Dishes
Free space ( Σ Vi )2 Guided
R.D. Ekers Dish of Dishes
Free space
Guided
(Σ Vi )2
R.D. Ekers Array of Dishes
Free space
Delay Guided Phased array (Σ Vi )2 R.D. Ekers Array of Dishes
Free space
∆Θ = λ/D
D
Delay Guided Phased array (Σ Vi )2 R.D. Ekers Beam Forming Array
∆t
(ΣVi)2 (ΣVi)2
I1 I2 R.D. Ekers Imaging
Array θ
Correlator
I(θ) R.D. Ekers TheThe VeryVery LargeLarge ArrayArray
NewNew MexicoMexico VLAVLA DD--configurationconfiguration HatHat CreekCreek RadioRadio ObservatoryObservatory HatHat CreekCreek RadioRadio ObservatoryObservatory
ATA
BIMA+OVRO = CARMA The Allen Telescope Array
• Joint project between SETI Institute and UCB Radio Astronomy Lab • Located at Hat Creek in N. CA • Goal of 350 6.1-meter antennas (and beyond) • Funded to-date primarily by Paul G. Allen Foundation ATAATA--350350 OriginalOriginal ““NebulaNebula”” ImagingImaging withwith ATAATA--350350 2.5o
1420 MHz
Snapshot image ImagingImaging withwith VLAVLA EE-- configurationconfiguration2.5o
1420 MHz
Snapshot image NumberNumber ofof Elements/ScheduleElements/Schedule
3.8% 4.6% 4.7% 5.2% Project Management 13.9% Integration & Test Antennas Signal Path 29.1% 6.7% Control Site Contingency Other 32.2%
~$29M*
*Full-cost accounting Introduction Antenna Signal Path Control Site Status ScienceScience GoalsGoals
• 3 year survey to map all Galaxies out to 300 Mpc and extragalactic clouds in HI • Frequent, fast all-sky surveys to explore transient phenomenon (~5 days) • Pulsar monitoring/survey • Magnetic field transition regions (Zeeman) • Large-scale surveys at other frequencies (e.g. CCS, H2CO, H2CS,C4H, CH3OH, OH, CH, CH2NH, CH3NH2, HCOOH, HC5N, HC7N, HC9N) • SETI Surveys Surveys Surveys
DesignDesign GoalsGoals forfor thethe ATAATA
Number of elements 350 Element diameter 6.1 m Total geometric 10,229 m2 collecting area 114 m Diameter equivalent Frequency 0.5 11.2 GHz Aperture efficiency 60 % Effective area 6,137 m2 2.2 K/Jy System temperature 42 K At 80 K 2 Ae/Tsys 146 m /K ~1% SKA Effective diameter 700 m Natural weighting Number of beams 16 Dual-pol FoV 40 0.07 deg2 (5 deg2 at 1420 MHz) Synthesized beam 216 9.8 arcsec TheThe ElectromagneticElectromagnetic SkySky
Microwave Window
ATA FlexibilityFlexibility
Beam former generates 16 dual-pol pencil beams anywhere in the sky (100 MHz) FlexibilityFlexibility
Beam former Correlator generates images the 16 dual-pol entire FoV pencil beams (200 MHz) anywhere @ ~20,000 in the sky pixels (100 MHz) FlexibilityFlexibility NULL
Beam former Correlator generates images the 16 dual-pol entire FoV pencil beams (200 MHz) anywhere @ ~20,000 in the sky pixels (100 MHz) NotNot JustJust Cheaper,Cheaper, butbut BetterBetter
z Exploits Large Primary FOV z Enables Simultaneous SETI and RA z Satellite Nulling Uses RA Imager
Steer the null Every beam needs a back end beam onto satellite 5 times Size of Full moon NullsNulls CancellationCancellation CostCost CurveCurve
Fixed area Fixed UWB Science drivers SignalSignal PathPath
Field Lab IP SignalSignal PathPath Antenna/FrontAntenna/Front--endend
Field Lab IP AntennaAntenna •6.1-meter offset Gregorian (2.4-meter secondary) •rim-supported, hydroformed dishes TipTip CurveCurve AntennaAntenna AntennaAntenna SurfaceSurface
• rms: 0.022” (0.56mm) • p-p: 0.118” (3mm) ShipmentShipment ShipmentShipment ManyMany AntennasAntennas ConstructionConstruction TentTent
DishDish AssemblyAssembly
Antenna/FrontAntenna/Front--endend
Field Lab IP FeedFeed 0.5 – 12.0 GHz
FrontFront--EndEnd Dewar/Dewar/CryoCryo
” 12 r rato rige Ref
ar Dew LNAs Balun/LNABalun/LNA ““ActiveActive BalunBalun”” FrontFront--endend PAXPAX PAMPAM OTXOTX FullFull SpectrumSpectrum
-40
-50
-60
-70 Power [dBm]
-80
-90 12345678910 Frequency [GHz] RFRF ConverterConverter
Field Lab IP DigitizerDigitizer
Field Lab IP IFIF ProcessorProcessor
Field Lab IP BackBack--endsends
IP ATAATA--350350 ConfigurationConfiguration
800 500 UVUV DistributionDistribution
ControlControl
• Java–based client-server JSDA (Java Simple Distributed Architecture) • TCP/IP, UDP/IP •Jythonscripting • SBC at each antenna does it’s own housekeeping • Hierarchical controllers thru processor • Monitor – less is more Introduction Antenna Signal Path Control Site Status BeamBeam PatternPattern ClientClient Spectrum Video Correlator Server Jython Server Hat Creek
Video Predict Server Client (satellites) Local
Corr. Client Antenna Server Local JSDA
Beam Pattern Client
M31M31 M33M33 Silo/HolographySilo/Holography
< 1mm rms TestsTests FeedFeed TestingTesting ReceiverReceiver TemperatureTemperature
UncertaintyUncertainty PrinciplePrinciple
0
9
8
7
6
5
∆t 4
3
2 ∆t ∆ν ≥ 1
1
0 ∆ν UncertaintyUncertainty PrinciplePrinciple
0
9 Nature never does 8
7
6
5
∆t 4 Technology can approach limit
3
2 ∆t ∆ν ≥ 1
1 Narrowband signals will be long 0 Short pulses will be broadband ∆ν SETISETI TargetedTargeted SearchSearch
−4 N 2 n = 2.3×10 * stars/PFOV N > 4288ν stars o ν 2 * TargetedTargeted SearchSearch
N* νmax Dmax Nciv Weather AOPR at [GHz] [pc] radar Dmax at Dmax 103 0.5 30 108 9 0.006
104 1.5 65 107 40 0.03
105 4.8 140 106 200 0.12
106 15.3 300 105 900 0.6
−4 ν < 2×10 N* GHz NearNear SkySky SurveySurvey
For 1 beam 20 AOPR (1 SKA) at 1.5 kpc 108 stars Æ 1000 civilizations FarFar SkySky SurveySurvey
For 1 beam 700 APR at 10.5 kpc www.seti.org astro.berkeley.edu/ral