A Minimal Space Interferometer Configuration for Imaging at Low Radio Frequencies

TL;DR

This paper proposes a minimal space interferometer configuration with three satellites in Low Earth Orbit to enable high-resolution imaging of the low-frequency radio sky below 20 MHz, overcoming ground-based observational constraints.

Contribution

It introduces a novel minimal satellite configuration and simulation-based analysis for low-frequency radio sky imaging with high angular resolution.

Findings

Achieves angular resolution finer than 10 arcsec at frequencies below 20 MHz.

Provides maximum (u, v) coverage with baselines over 15000 km through orbital design.

Demonstrates the system's potential for exploring the unexplored low-frequency radio sky.

Abstract

The radio sky at lower frequencies, particularly below 20 MHz, is expected to be a combination of increasingly bright non-thermal emission and significant absorption from intervening thermal plasma. The sky maps at these frequencies cannot therefore be obtained by simple extrapolation of those at higher frequencies. However, due to severe constraints in ground-based observations, this spectral window still remains greatly unexplored. In this paper, we propose and study, through simulations, a novel minimal configuration for a space interferometer system which would enable imaging of the radio sky at frequencies well below 20 MHz with angular resolutions comparable to those achieved at higher radio frequencies in ground-based observations by using the aperture-synthesis technique. The minimal configuration consists of three apertures aboard Low Earth Orbit (LEO) satellites orbiting the Earth in mutually orthogonal orbits. Orbital periods for the satellites are deliberately chosen to differ from each other so as to obtain maximum (u, v) coverage in short time spans with baselines greater than 15000 km, thus, giving us angular resolutions finer than 10 arcsec even at these low frequencies. The sensitivity of the (u, v) coverage is assessed by varying the orbit and the initial phase of the satellites. We discuss the results obtained from these simulations and highlight the advantages of such a system.