Attitude Detection of Buccaneer RMM CubeSat through Experimental and Simulated Light Curves in combination with Telemetry Data M. Cegarra Polo, R. Abay, S. Gehly, A. Lambert, P. Lorrain, S. Balage, M. Brown and C. Bright School of Engineering and IT, UNSW Canberra Space, Canberra, Australia ABSTRACT Identification and characterisation of the growing population of resident space objects (RSOs) in orbit around Earth is central to current and future Space Traffic Management and Space Situational Awareness (SSA) activities. Research at University of New South Wales (UNSW) Canberra Space seeks to assist this effort through combining optical measurements of selected RSOs with numerical astrodynamics modelling techniques to extend the information that can be inferred about an RSO from its photometric light curve signature. The initial phase of this research comprised two three-month observation campaigns, which were completed in July 2018. A collection of photometric light curves was obtained using different nodes of the Falcon Telescope Network (FTN) for the Buccaneer Risk Mitigation Mission (BRMM) 3U CubeSat. The BRMM was launched in 2017 as a joint mission between UNSW Canberra Space and the Defence Science and Technology Group (DST). While BRMM is a pathfinder for the future Buccaneer Main Mission whose primary objective will be the calibration of the Jindalee Operational Radar Network (JORN), it also serves as a stepping stone in building Australian space capability. For BRMM one of the mission objectives was to perform photometric experiments to contribute to SSA research and development efforts via dynamic on-orbit manoeuvres. This paper reports on the initial analysis of the photometric light curves central to the SSA mission goal. The material properties and dynamic attitude motion of the BRMM during the FTN observations are known, with rotational body rates commanded from 0.2 to 5 degrees per second about multiple combinations of body axes to build a comprehensive database of light curves for analysis. Further variation in the light curve database is provided by observations obtained prior to solar panel and antenna deployment. A set of 70 light curves was obtained during the observational campaigns, with each light curve signature containing a bulk change in intensity over time due to the change in range as BRMM approaches the FTN node on its Low Earth Orbit (LEO) trajectory. Superimposed on the mean intensity change are characteristic peaks and troughs produced by reflections from individual facets of the spacecraft, the magnitude and frequency of which are highly dependent upon the spacecraft’s attitude and body rate. Samples from the light curve database are presented with the attitude data downlinked from the spacecraft to assess light curve variations with attitude and spin rate of the spacecraft. Supporting the optical data are numerically simulated light curves, generated by applying the Ashikhmin- Premože Bidirectional Reflectance Distribution Function (BRDF) Model for the BRMM geometry using a high- fidelity 6 Degree of Freedom (DOF) orbit propagator supported by the Orekit orbit propagation library for computations related to time systems, coordinate frames, and gravitational perturbations. The performance of the numerical simulation was evaluated by superimposing the attitude profile reported by the spacecraft telemetry on top of the propagated orbit to provide a one-to-one comparison between the measured and simulated light curves for select cases. A preliminary investigation into the feasibility of using the simulation tool to infer attitude dynamics from a given light curve signature is also presented. A candidate set of simulated light curves was generated by numerically propagating a set of initial attitude states and constant body rates through the observation window. The results were searched to find the case that provided the best fit to the observed light curve. A further study was initiated to investigate the errors introduced by the assumption of a constant body rate throughout the observation for the simulated light data. 1 INTRODUCTION Small satellites show a relatively high mission failure rate during their lifetime compared with other spacecraft, which combined with the fact that most of them don’t have effective thrust systems, makes them a potential source of space debris in the currently overcrowded LEO orbit. This issue has been aggravated in recent years by the growth of this type of satellite and this trend seems unlikely to diminish, with approximately 120 from a Copyright © 2018 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com