the eight-meter-wavelength transient array - virginia tech
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TheEight-meter-wavelengthTransient Array
Steve Ellingson Dept. of Electrical & Computer EngineeringCameron Patterson Dept. of Electrical & Computer EngineeringJohn Simonetti Dept. of Physics
Virginia Polytechnic Institute & State University
September 30, 2004
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ETA is…
A new radio telescope designed specifically to detect the radio-frequency emission associated with the explosions of a broad class of astronomical objects (“transients”)
An NSF-funded project begun August 2005 (Just getting started…)
A collaboration between the Virginia Tech Departments of Electrical & Computer Engineering and Physics
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ElectronicsHut
Dipole Station(12 Dual-Pol Dipoles)
Dish Station(Loop Feed on
26 m Dish)
Internet Access
~ 1 km
The Dynamic Radio Sky
Historically – and understandably – we tend to think of astronomical events unfolding over very long time scales
So, discovery of astronomical events occuring over shorter timeframes tends to be a surprise. Classic examples:
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PulsarsPeriodic pulsed emission from neutron stars was predicted, but unexpected
Detection by accident (1967)
The surprises continue:
– Giant pulses (1968): Rare pulses of > 100 times the mean intensity. Only a few pulsars are known to make them.
– Nanogiant Pulses (2003): For a few nanoseconds at a time makes a pulsar the “brightest” object in the sky!
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Gamma Ray Bursts (GRBs)Not anticipated before discovery
Discovery completely by accident (and not even by astronomers!)
Still murky on what makes them… could be several different sources
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What Might a New Transient Search Find?
More / stranger pulsars, through (for example) giant pulse emission
GRB prompt emission
Supernovae (prompt emission)
Exploding Primordial Black Holes (PBH)
Coalescing Exotic Binaries– Neutron Star – Neutron Star– Neutron Star – Black Hole
All the other stuff we don’t know about yet!
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Why Radio Transients Are Interesting
Can be used to confirm / refine theoretical models for the progenitor objects, which are very strange
They provide “search lights” for exploring the interstellar / intergalactic medium
Strong + short duration implies extremely high energy at the source - Ready-made laboratories for exploring the frontiers of physics
Confirm / refine fundamental physics, including cosmology (PBHs)
http:\\www.ece.vt.edu\swe\eta
ElectronicsHut
Dipole Station(12 Dual-Pol Dipoles)
Dish Station(Loop Feed on
26 m Dish)
Internet Access
~ 1 km
http:\\www.ece.vt.edu\swe\eta
Eight-meter-wavelength Transient Array (ETA)
ElectronicsHut
Dipole Station(12 Dual-Pol Dipoles)
Dish Station(Loop Feed on
26 m Dish)
Internet Access
~ 1 km
http:\\www.ece.vt.edu\swe\eta
Eight-meter-wavelength Transient Array (ETA)
About 1/2 of the collecting area is in the form of an array which
continuously observes the entire skyusing fixed “patrol beams”
ElectronicsHut
Dipole Station(12 Dual-Pol Dipoles)
Dish Station(Loop Feed on
26 m Dish)
Internet Access
~ 1 km
http:\\www.ece.vt.edu\swe\eta
Eight-meter-wavelength Transient Array (ETA)
About 1/2 of the collecting area is from a dish that allows follow-up, diagnostics & more sensitive observation of a smaller
portion of the sky
Location
http:\\www.ece.vt.edu\swe\eta
PisgahAstronomicalResearchInstitute(PARI)
Knoxville
Greenville
Asheville
Eight-Meter (29-47 MHz) Feed Modification
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Artist’s Impression of “Core Array”
16 m diameter (2λ @ 38 MHz)
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A/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IF
RFRFRFRFRFRFRFRFRFRFRFRF
Dip
ole
Arr
ayETA System Design
AB x2AB x2AB x2AB x2AB x2AB x2AB x2AB x2AB x2AB x2AB x2AB x2
ActiveBalun
100-500 ftCoax
125 MSPS x 12-bit(Digital Receiver,
Interference Mitigation)
-15.5 dBm in [30,85] MHz
Measurements taken@ PARI (Rosman, NC).Spectrum analyzer (∆ν=300 kHz) at end of feedline
Max HoldIntegration
Interference Mitigation
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PCPCPCPC
NodeNodeNodeNode
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A/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IFA/D-IF
RFRFRFRFRFRFRFRFRFRFRFRF
Dip
ole
Arr
ayETA System Design
AB x2AB x2AB x2AB x2AB x2AB x2AB x2AB x2AB x2AB x2AB x2AB x2
NodeNodeNodeNodeNodeNodeNodeNodeNodeNodeNodeNode
2 G
b/s
Seria
l Int
erco
nnec
t Mat
rix
ActiveBalun
100-500 ftCoax
125 MSPS x 12-bit(Digital Receiver,
Interference Mitigation)
432 Mb/sLVDS
16-NodeFPGA Cluster
(Beamforming)
4-NodePC Cluster
(DedispersionSearch)
1 Gb/sEthernet
Dedispersion
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Cordes & Lazio (2001)
Free electrons in deep space stretch (“disperse”) a short (<1 s) pulse into a “chirp” lasting minutes to hours!
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ETA Sensitivity Projections
Year 1 Goal
Why Would Engineers be Interested?
ETA advances the state-of-the-art in many areas simultaneously:– Wideband antennas – High dynamic-range direct-sampling receivers– Real-time DSP using reconfigurable FPGA clusters– PC Cluster Computing– Array Signal Processing– Interference Mitigation
For more information:– Web site– S. Ellingson (ECE), Antennas, Receivers, Signal Processing– C. Patterson (ECE), Reconfigurable Computing– J. Simonetti (Physics), Astrophysics
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