Pegasus Project Technical Report

This paper is a theoretical study about the implementation of a Global Navigation Satellite System around the Moon. The objective of the study is to investigate from the feasibility to the implementation of such a system within the framework of a broader project which aims to see humans activities back on the Moon in the next decade. In that order, the system is complying with technical specifications as defined by a client. The rationale behind the system is that to reach a satisfying level of performance - and therefore meet the client’s requirements - a constellation of twenty-one satellites spread out on three orbits around the Moon at a constant semi-major axis of 10,000 [km] is needed. The constellation is named after the Greek divinity Pegasus and in reference to the star constellation. Each orbit is set at an 80 [◦] inclination and respectively spaced at 120 [◦] from one another with regard to their Right Ascension of Ascending Node. There are seven satellites per orbit. Every Pegasus’s satellites carry on-board four atomic clocks, three Emergency Broadcast System antennas, two Tracking, Telecommand and Control antennas and one navigation antenna. Maneuvers for station-keeping and end-of-life are ensured by four 1500 [W] hall effect thrusters mounted on two robotic arms with six degrees of freedom. 150 [kg] of Xenon will be used as propellant so that the mission can be carried out for at least ten years. A Pegasus satellite has a dry mass of 711.04 [kg] and a wet mass of 860.64 [kg]. Regarding the service provided on the lunar surface and its low orbit, the Pegasus constellation guarantees a 100% GNSS and Emergency broadcast availability with a 6.80 [m] global precision at 3σ and a 33 [ns] time precision. All the subsystems are powered by a 50 [V] Power Conditioning Unit and 165 [Wh/kg] Li-on battery which will be recharged by 15 [m2] of solar panels and used during eclipses. The overall dimensions of one Pegasus spacecraft are 2.34 [m] × 1.480[m] × 1.284[m]. One full orbital plane of the constellation can be launched by one Ariane 64, which guarantees its implementation with only three launches, fulfilling a deployment time span inferior to a year