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We propose a dense network of dual-mission HF radars costing $300 -- PiRadar costs 95% less than contemporary radar nodes using the latest COTS SDR technology, simultaneously:
- polarization-sensitive ionosphere probing with 1-25 km range resolution
- relaying data over the horizon at 1-20+ kpbs rates
This capability enables deployment of networks dense and distributed enough to make real-time 3-D images of the ionosphere at a cost far less than traditional single-site radars.
Each PiRadar node will cost about $300 for the basic hardware, enabling high resolution/bandwidth polarization-sensitive nodes (dual TX, dual RX). Inexpensive USB HDD data storage means the PiRadar can be deployed and left unattended for years, relaying the most important data over the air while retaining a large long-term database.
This is a price point that citizen scientists and primary school science classes can build and deploy. The PiRadar nodes work together as an infrastructure-less self-organizing network, transmitting pseudonoise CDMA waveforms hundreds of kilometers in the shortwave radio bands. PiRadar waveforms simultaneously measure ionospheric characteristics and contain data relayed through the mesh to other nodes or to internet destinations.
Each open-source PiRadar node contributes to:
- improving ionospheric models via measurements as an alternate or complement to GNSS TEC measurements
- 4-D imaging of the Earth’s atmosphere/ionosphere
- data relay from isolated sites (e.g. flood alarm, tracking animals)
- Solar storm impact detection and quantification
- Ground-based GPS time-transfer and location service alternative
- High resolution radar/broadband data: Red Pitaya SDR dual-channel RX/TX v1.1 came to market October 2016 for 149 Euro ($166) educational pricing
- Spread spectrum / CDMA resiliently trades instantaneous RF bandwidth for SNR like GPS does using Shannon-Hartley Theorem: C=B*log_2(1+S/N) where B is bandwidth and C is channel data capacity.
Hysell, Milla, Vierinen "A multistatic HF beacon network for ionospheric specification in the Peruvian sector" describes a 3-site system comprised of one dual-frequency transmitter using similar coding at 1/2 Watt, and two receiver sites, all synchronized via GPS. One of the key factors noted in the work was the immense oversampling of the received signal, implying that a much more modest SDR might be used.
HF Radar echogram from JGR 2016 A multistatic HF beacon network for ionospheric specification in the Peruvian sector. Color ~ Doppler shift
- BU Engineers without Borders did a clever project in Naluja, Zambia using long-range line of sight transmission of microwave signals.
- In mountainous rural regions, line-of-sight links are difficult to impossible due to topology. Regions in Afghanistan, Nepal, Tibet, et al. or even Colorado -- PiRadar can communicate clinic info, landslide detectors, dam overflow detectors, etc.
- Sometimes a landslide blocks a river say in rural China or Nepal. No one knows about it, and some hours or days later the natural dam breaks through and washes a village away with virtually no warning.
- Aberfan disaster in Wales. There was only 90 seconds of time from start to finish due to the direct impact of the landslide (not an overflow, just the dirt itself). Still, 90 second warning could have many lives.
- Northern California a drain plugged, leading to large damage through a sequence of events. ( no cellular coverage in that large area)