SSA Experiments for the Australian M2 Formation Flying CubeSat Mission

UNSW Canberra has a program of experiments onboard the M2 formation flying CubeSat mission to provide truth data for available space situational awareness (SSA) sensors and modelling algorithms. The paper outlines the program of experiments and deployments planned throughout the early, main, and extended operation phases of the mission that provide opportunities for SSA observations. The mission comprises 2x6U CubeSats. Each satellite uses a 3-axis attitude control system to exploit differential atmospheric drag forces between the spacecraft to control the along-track formation. The differential aerodynamic formation control enables the satellites to remain within an acceptable alongtrack offset to perform the main mission experiments. Several important opportunities to collect benchmark SSA data are present throughout the mission. The CubeSat pair are initially conjoined as a 12U satellite and, following a scheduled command from the UNSW Canberra ground station, will be impulsively pushed apart in the along-track direction by a spring to create a formation of 2x6U satellites. The separation of the spacecraft, followed by solar panel and antennae deployment, mark significant changes to the configuration, radar cross section, and orbit, during this early operations phase. The solar panel deployment increases the maximum frontal area of the spacecraft from 0.043 m2 in stowed configuration to 0.293 m2 when fully deployed. The attitudes of the spacecraft will be controlled to arrest the along-track separation of the spacecraft via the action of differential aerodynamic drag. The satellites feature GPS and attitude determination and control for accurate time, position, velocity, and attitude information, which is routinely available in the satellite telemetry. The change detection experiments planned for the mission use the US Air Force Academy (USAFA) 0.5 m raven class Falcon Telescope Network and UNSW Canberra’s 0.36 m Rowe-Ackermann Schmidt Astrograph (RASA). Photometry and astrometry from these sensors are used in combination with synthetic sensor data through application of novel machine-learning frameworks to provide estimates for the satellites’ configuration status and attitude profile during the observations. The synthetic optical sensor data will be produced from an in-house high-fidelity GPU accelerated ray-tracing simulation tool that can model multiple reflections and account for complex material reflectance properties. Progress on the development of the GPU tool are presented. The latter stages of the mission investigate advanced differential aerodynamic control methodologies. The impact of sensor uncertainty and operational constraints on the accuracy of differential aerodynamic formation control manoeuvres will be analysed and quantified during the mission. A modelling and simulation framework will employ coupled ionosphere/thermosphere models with high fidelity force propagation tools to provide higher fidelity estimates of the non-conservative forces imparted on the spacecraft by the atmosphere than standard models provide. The extended mission phase contains an ambitious space environment research experiment that seeks to measure ‘ionospheric aerodynamics’ effects imparted on the spacecraft. The experiment has been developed from theoretical and numerical research at UNSW Canberra that studies the force created when a charged body interacts with the weakly ionized plasma in the ionosphere in LEO. The interaction is controlled from charge plates located on the extremity of the extended solar panels. The configuration and concept of operations are presented.