Home
Remote sensing of the upper atmosphere of earth has historically included giant radars costing $100M (e.g. Arecibo). We propose an inexpensive radar network costing less than $200 per node that citizen scientists and primary school science classes can build and deploy. The radar nodes work together as an infrastructure-less self-organizing network, transmitting pseudonoise waveforms hundreds of kilometers in the shortwave radio bands. The waveforms simultaneously measure atmospheric characteristics and contain data relayed to the cloud for offline processing for purposes including:
- improving ionospheric models vis 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
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.
We believe we can do even better than this at 10% the hardware cost using Red Pitaya
Initial experiments show that the CPU & PLL on the Raspberry Pi 3 may be capable of transmitting HF radar waveforms with sufficient spatial resolution to resolve interesting atmospheric disturbances. System architecture is highly flexible, and nearly any single-board computer may be suitable. $10 DDS chips like the AD9834 allow synthesizing frequencies from DC to VHF with arbitrary modulation.
An RF receiver is necessary; one option is using a $20 RTL USB stick with a $50 upconverter board. The radar system will be documented and described sufficient for a “hackaday” type article enabling citizen scientists and school teachers to build and deploy their own. Designing a custom PCB will allow substantial cost reduction, critical for adoption in economically disadvantaged areas.
The PiRadar system has two primary functions
- data transceiver-long range (> 100 km) broadband HF
- ionospheric radar
The problems these systems have in common for our experiments and deployments include
- too expensive radios ~$1000 ham radio transceivers
- too little instantaneous bandwidth: < 3.5 kHz typically.
These systems fail to use Shannon-Hartley theorem optimally. One can trade bandwidth and/or time for power<-->SNR. In essence we are proposing a more optimal use of scarce RF resources by using low-power pseudonoise broadband waveforms that other users will scarcely detect.
Numerous other crowd-sourced radio science projects out there, including:
- Radio Jove 20 MHz receiver network listening to Jupiter's decametric radiation. Seems to use spectrum vs. time.
- Aurorasaurus actually for optical measurements, but has great citizen use and visualization.
DDS waveform generation (we might be interested in Figure 6 operation)