On the detection of low-frequency planetary radio emission with an orbiting interferometer

Abstract

The magnetized planets of the outer Solar System produce kilometric radio emissions at very low frequencies (< 1 MHz). They reveal the planetary magnetic dynamics and their interaction with the solar wind. Those radio emissions can also serve as a proxy for interplanetary space weather monitoring. Space-borne radio interferometers will offer new capabilities for measuring planetary low-frequency radio emissions as they are not limited by the Earth's ionospheric cutoff (∼ 10 MHz) and can provide spatially resolved observations. This study is conducted in the context of the NOIRE—Nanosatellites for a Radio Interferometric Observatory in Space—concept study. The observation of planetary radio emissions is part of its main scientific objectives and should be achievable with an array of 50 satellites. The instrument's sensitivity is studied with a detailed description of the noises and errors involved in the measurement process. We then detail the various planetary radio components that can be studied with the given instrument design and the constraints currently known at this stage of the project. We discuss how the design may be optimized to better suit these scientific objectives, and we discuss the data volumes involved. The results suggest that NOIRE is able to produce dynamic spectra for Jupiter and Saturn with temporal and spectral resolutions good enough for phenomenological studies and long-term studies. They also suggest that Uranus' and Neptune's emissions may be detected, but with a low revisit rate (∼ 1 point every 4 hr).