Auroral Radio Emissions Simulation and Processing for AERO CubeSat Mission

Auroral Emission Radio Observer (AERO) is a NASA H-TIDeS-funded 3U CubeSat mission with the main objective of observing Earth's radio aurora. AERO will conduct a three-month mission in polar orbit to measure the direction of arrival, frequency spectra, and occurrence rates of radio frequency emissions from Earth's aurora. AERO will also advance the technology readiness level (TRL) of its vector sensor payload. The vector sensor (VS) has six mutually orthogonal loop and dipole antennas that detect all six electromagnetic wave components. VS technology allows for direction of arrival calculations of signal sources with a single antenna in a compact space. To facilitate testing and performance studies of the VS payload, we have created an end-to-end simulation of the AERO data collection system that is designed to simulate and process synthetic voltage data from the VS. The VS simulator includes the following elements: modelling the spacecraft orbit, simulating auroral signals, and implementing real-time signal processing. A precise prediction of spacecraft orbit is created using AGI's Systems Tool Kit (STK), constrained to altitudes of 450 to 550 km and a noon/midnight polar orbit with a target local time of midnight. This model is used to generate the position of the spacecraft at a given time in the mission life. Simulated auroral radio point signals with various polarizations, intensities, and frequency spectra are used to simulate four major types of auroral radio emissions: Auroral Kilometric Radiation, Medium Frequency Burst, Auroral Hiss, and Auroral Roar. Stationary, grouped, and banded point sources are all explored as possible emission types. In addition to the spacecraft location and orientation, these point sources are superimposed with expected ambient radio noise and then split into a six-channel VS simulator which produces voltage time series data. The voltage signals are then put through a signal processing chain implemented on a field programmable gate array (FPGA). Implementing the FPGA results in a prototyped system that receives data in real-time as it is passing through the auroral zone which is simulated from the VS simulator. It executes signal processing calculations in parallel at the same moment that data is coming in from the VS. The AERO CubeSat's anticipated launch date is January 2022 and will perform the first localizations of Earth's auroral emissions. Ultimately, this end-to-end simulator will allow for the testing of advanced signal processing algorithms for the VS and assist in data analysis for the AERO CubeSat mission.