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.