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The US agency has launched a program aimed at developing new space-based technology capable of better assessing high-frequency transmissions in the ionosphere to bolster warfighting communication capabilities.
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The Defense Advanced Research Projects Agency (DARPA) has unveiled the Ouija program, which aims to deploy sensors on low-orbiting satellites to provide new insights into high-frequency (HF) radio wave propagation in the ionosphere.
The HF transmissions – ranging from the upper edges of the Earth’s atmosphere to the lower regions of space – would be quantified to improve characterisation of the ionosphere, ultimately enhancing warfighting technology.
Warfighters leverage HF radio transmissions to operate military systems across space, air, ground, and maritime domains.
Current analyses of HF signals in the ionosphere rely on ground-based methods.
“Ouija will augment ground-based measurements with in-situ measurements from space, in very low-Earth orbit (VLEO), to develop and validate accurate, near real-time HF propagation predictions,” Jeff Rogers, Ouija program manager in DARPA’s strategic technology office, said.
“The VLEO altitude regime, approximately 200 km-300 km above Earth, is of particular interest due to its information-rich environment where ionospheric electron density is at a maximum.
“Fine-grained knowledge of the spatial-temporal characteristics of electron density at these altitudes is required for accurate HF propagation prediction.”
The Ouija program includes two technical areas, with the first seeking to develop, qualify, launch, and operate multiple small satellites carrying scientific and mission instrumentation.
The payload will be designed to measure electron density by both direct sampling and indirectly via radio occultation using navigation satellites.
This is expected to involve leveraging commercial-off-the-shelf (COTS) components, supported by innovative instrumentation proposals that enhance the functionality of the scientific payload over a COTS baseline.
“The HF mission payload will require a high sensitivity, high dynamic range, low noise HF measurement subsystem,” Rogers added.
“The antenna for this subsystem is a particular challenge, as efficient HF antennas that operate at the lower end of the frequency band are long, presenting deployment and space vehicle drag challenges.”
The second technical area aims to develop assimilative models that ingest direct, in-situ, measurements of electron density from a satellite in VLEO, with models to be fed into HF propagation code validated with data measured on-orbit.
This could improve fidelity over current assimilative models by incorporating high resolution local measures with low latency updates.
[Related: DARPA advances program to counter hypersonic threats]
