PiRadar Project Connecting Low-Cost Radar Nodes for Ionosphere Imaging

This isn’t the first time we’ve talked about low-cost self-made radar systems here. A previous article already presented an ambitious FCMW radar project you could almost build on your kitchen table, without even mentioning the “coffee can radars” that literally use empty cans as radar antennas. But if detecting an object’s position and speed is one thing, using a similar setup to build an array for imaging the Earth’s atmosphere and ionosphere – the upper part of the atmosphere, ionized by solar radiation and mainly used for its reflective capacity with regard to radio waves, especially in the HF domain – takes the basic idea much further.

Some time ago, J. Vierinen developed the PiRadar project, in which an arbitrarily shaped array of low-cost radar nodes would be used for imaging purposes, in an analog fashion as in ultrasonic non-destructive testing of materials, structural welds, etc. The next figure shows a conceptual view of the array, and how the sequencing of signal emission and reception is used to reconstruct an image of the ionosphere. The considerable distance between the nodes gives a good idea of the vast dimensions of the project.

The PiRadar allows polarization-sensitive ionosphere probing with 1 to 25 km range resolution to produce 3D-images of the Earth’s atmosphere and ionosphere, and can also be used as over-the-horizon data relay at 1 to 20 kbps rates.

This setup, aimed at maximum simplicity for budgetary reasons, uses only one antenna for transmission and reception, as can be seen in the figure below. Connected to the antenna are both in- and outputs of a Red Pitaya board, in turn communicating with a Raspberry Pi3 unit. The sum of all these commercial-off-the-shelf components brings the price of one node to a total of around $300, just a fraction of what a traditional radar system would cost.

But the goal of this project doesn’t just involve the development of a low-cost radar, it’s also about sharing the design, allowing amateur scientists, students, and others to build their own device and connect it to the PiRadar network, thus collaborating in an infrastructure-less, self-organizing project. Which, come to think of it, is pretty much the basic philosophy of Red Pitaya.