Broadband receiver for VLF on-orbit wave-particle interaction experiments

Abstract

A broadband, multi-channel Very Low Frequency (VLF) radio receiver (BBR), developed as a sensitive analog, vector wave receiver for whistler-mode signals in the VLF range, was successfully flown on the Air Force Demonstration Science Experiment (DSX) Mission to Mid-Earth Orbit (Johnston et al., 2023, ). The BBR is a radiation resistant, 5 x 2 channel receiver, integrated into the Wave Induced Precipitation of Electron Radiation (WIPER) instrument package on DSX. The BBR accepts electric wave signal inputs from (a) an 81.6 m tip-to-tip dipole VLF antenna on the DSX Y-boom, (b) a 16.3 m tip-to-tip dipole antenna on the DSX Z-boom, and (c) signals from a Tri-Axial Search Coil (TASC), an three-orthogonal axes magnetic wave search coil magnetometer mounted on the DSX + Z boom. The electric and magnetic VLF signals are processed in the BBR by two independent, radiation hardened five channel receivers: (a) a receiver of heritage design with commercial off-the-shelf components (COTS), and (b) a micro-receiver incorporating custom, radiation resistant, micro-electronics. The bandwidth of all five channels in both the heritage and micro designs covers from 10 Hz to 50 kHz. A software "receiver", SRx, running in the on-board flight computer, the ECS, manages the BBR's data flow and data delivery to the ground. The SRx additionally computes supporting science data products such as Fourier transforms, multi-band filters and cross correlations among the BBR's electric and magnetic field channels to facilitate production of VLF wave normals. Plain Language Summary A Broad Band VLF Receiver (BBR) was designed, implemented, flight tested and flown on the AFRL DSX mission in medium Earth orbit (MEO). The BBR receives voltage waveforms from VLF electric and magnetic field antennas on-orbit, amplifies, conditions, digitizes the input signals and delivers the sampled waveforms to the DSX spacecraft's on-board computer for storage, processing and transmission to the ground. In so doing, the BBR supported experiments in controlled loss of energetic trapped radiation belt particles via in-situ VLF wave injection and whistler wave resonant scattering.