Flexible Radio Array for Ionospheric and Atmospheric research (FRAIA)

We present the Flexible Radio Array for Ionospheric and Atmospheric
research (FRAIA). FRAIA consists of 18 relocatable RF receiver
stations with the capability to receive in the VLF band (0-50 kHz),
the HF/VHF band (3-85 MHz), as well as at discrete beacon satellite
frequencies 150, 400, and 1067 MHz. The antennas are monopole for the
VLF reception, all-sky broad-band crossed dipoles for the HF/VHF band,
and co-centric all-sky quadrifilar antennas for the beacon satellite
bands. Each station contains a 8-core CPU and a high-end
software-defined radio for real-time sampling and processing of the RF
signals. Each station include GPS timing to 50 ns, and three
synchronization devices allows for the 18 stations to be used together
in a single phased array or up to three phased arrays. FRAIA stations
can be used for observing VLF whistler waves, receiving standard
VHF/UHF beacon satellite signals for ionospheric tomography, for
riometry, for lightning observations and lightning interferometry, as
ionosonde receivers, HF radar receivers, over-the-horizon radar
receivers, and receivers for a future HF beacon satellite which we
propose, for ionospheric tomography.