Low cost low power ionosonde for dense sensor
networks
Juha Vierinen, David L. Hysell, Marco Milla, Jorge L. Chau
and Frank D. Lind
MIT Haystack Observatory
Sodankylä Geophysical Observatory, Finland
Cornell University
Jicamarca Radio Observatory, Peru
December 3, 2013
Previous work
I
A lot of previous work, starting from Hertz, Marconi,
Heaviside, Breit and Tuve (1926), Lassen (1926), Appleton
(1931)...
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Many, many others (eg., Budden 1961, Jones and Stephenson
1975).
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Monitoring traveling ionospheric disturbances (Crowley and
Rodrigues 2012, Crowley et al., 1987)
Software defined chirp ionosonde receiver
Video (virg.mp4,cyprus.mp4)
Multi-static HF radar equation
Continuous coded transmission
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Continuous transmit and receive, cyclic convolution
assumption valid due to long coherence
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Multiple simultaneous transmitters using the same channel.
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Perfect codes exist for T = 1 (Frank and Chu codes)
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Pseudorandom sequences are very close to optimal for R N.
3D electron density inversion using HF radio propagation
Airplane
Low cost ionosonde
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With a small change in software, and an antenna tuner, the
radar would effectively be an ionosonde.
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If an ionosonde could be made as cheap as a GPS TEC
receiver, there would be a possibility to operate a dense
network of ionosondes and get high quality ionospheric
profiles.
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A low power ionosonde that basically transmits noise wouldn’t
cause as much interference to others, and it would be more
easy to license.
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The orthogonality of pseudorandom signals would allow
oblique soundings between ionosondes within a network – and
again, with the help of ray-tracing, the study of even smaller
spatial scales.
$5000 Suitcase ionosonde
Tunable magnetic loop
for transmit
Laptop and software defined radio
Active broadband
magnetic loop for
receive
Very little interference
Dense network of low cost ionosondes
3D electron density inversion using HF radio propagation
Dual polarization
Monostatic
Ordinary mode
Extraordinary mode
Single hop
Double hop
Dual frequency
Bistatic
Single hop
Double hop
Low freq
High freq
Sketch of a solution
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Use electron density profile measured with Jicamarca as
background profile
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Parametrize the ionosphere to consist of the Jicamarca profile
and some small spatial deviation Ne (~s , θ).
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Measurements: propagation time between stations i, j: τi,j,ω,p ,
angle of arrival between stations i, j: φi,j,ω,p .
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Employ efficient ray-tracing methods (Jones and Stephenson
1975) to solve the forward theory of radio wave propagation in
magnetoionic plasma. m = f (θ) + ξ
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Use some iteration to solve a posteriori density p(θ|m).
6 MHz
500
Altitude (km)
400
300
200
100
0
40
44
46
48
50
Latitude (deg)
54
GNU Ionospheric Tomography Receiver (jitter)
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New low cost software defined dual beacon satellite receiver.
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Can receiver multiple transmitters simultaneously, supports all
beacon satellites.
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About ten receivers already build and in operation, more to
come.
GNU Ionospheric Tomography Receiver (jitter)
GNU Ionospheric Tomography Receiver (jitter)
700
600
500
4e+11
400
300
200
2e+11
100
1e+11
o
0
altitude
3e+11
58
60
62
o
64
66
latitude
0e+00
o
68
70
72
Conclusions
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Low cost, small form factor, and low power ionosondes
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Broad band noise-like signals, which do not interfere with
other users of the band.
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Almost nothing interfers with noise-like waveforms, they are
statistically orthogonal to RFI. No problems with RFI.
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Simultaneous multi-static capability using statistically
orthogonal waveforms.
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Very high time resolution ionograms (down to 10 seconds is
easily possible).
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Each ionogram point also contains a Doppler spectrum,
making interferometry and even imaging much easier.
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A network of multi-static ionosondes would greatly improve
global scale ionospheric monitoring capability when combined
with eg., GPS TEC and beacon satellite receivers in
multi-data source inversion (Bernhardt et al., 1998)