DARPA is seeking companies to develop real-time modeling for assimilative ionospheric and high-frequency (HF) radio propagation. The project – called Ouija TA-2 – is expected to improve communications and sensing.
HF signals are reflected by the ionosphere – the ionized part of the upper atmosphere of Earth – which affects radio propagation. This reflection is used to propagate signals for long distances by bouncing them off the ionosphere. Problems in transmission can arise due to static from thunderstorms and other radio frequency interferences, as the ionosphere is constantly changing from minute-to-minute, and from season-to-season.
The primary objective of the Ouija TA-2 project is to predict the characteristics of the ionosphere at unprecedented resolution and fidelity in near-real-time. Computer models need to be developed that can mimic ionospheric disturbances at scales of 100 kilometers and below. The models would use data collected by scientific instrumentation packages to be flown on the Ouija TA-1 CubeSats in very low-Earth orbit (VLEO), in addition to standard vertical and oblique sounder data.
Another goal of the project is to develop high-fidelity HF radio propagation models to help predict ground-to-VLEO radio wave propagation. The models will be validated using on-orbit measurements taken from the Ouija spacecraft HF payload, which will receive test signals from cooperative terrestrial transmitters.
The first phase will last 9 months and will begin modeling before data from the Ouija VLEO satellites is available. Instead, it will use sounder measurements from a terrestrial HF radio transmitter to low-Earth orbit (LEO) satellites equipped with an HF receive payload. The one-year second phase will assimilate data from one VLEO satellite and produce electron density distributions. The 16-month third phase will assimilate on-orbit data from six Ouija satellites.