L‑FIRE: a pathfinder for space-based interferometry at ultralow radio frequencies

Abstract

Ultra-low-frequency radio astronomy below 10 MHz remains the least explored region of the electromagnetic spectrum. Ground-based observations are fundamentally limited by ionospheric opacity, propagation effects and terrestrial radio-frequency interference. Space-based interferometry offers a pathway to overcome these limitations, but distributed observatories are often assumed to require tightly controlled formations and continuous station-keeping. L-FIRE (Low-Frequency Interferometric Radio Explorer) is a mission concept for a space-based radio interferometer operating between 1 and 40 MHz using a swarm of CubeSats in low-Earth orbit. Exploiting the relaxed coherence requirements associated with metre-scale wavelengths, the mission adopts a dynamically evolving formation in which natural orbital motion is treated as a design feature rather than a disturbance. By combining distributed sensing, small-satellite technologies, and dynamical formation flying, L-FIRE establishes a scalable architectural framework for future space-based interferometric observatories while enabling access to a largely unexplored region of the radio spectrum (below 10 MHz).