ESA GNC Conference Papers Repository

LEO satellite attitude guidance & control design for widely-varying solar beta angles
L.O. Ottone, J.B.F. Frappe, A.H. Hyslop
Presented at:
Salzburg 2017
Full paper:

The paper describes the design of the Attitude Determination and Control Subsystem (ADCS) performed by LuxSpace in the frame of the E-SAIL project. E-SAIL is an ESA Artes Public Private Partnership initiative, with exactEarth as customer and Luxspace as satellite prime. It has resulted in the development of a low-cost micro-satellite for the receiving of AIS (Automatic Identification System) signals, scheduled for customer delivery in 2018. As is common for micro-satellites, opportunity launches are very attractive, which potentially results in a plethora of orbits. As a consequence the ADCS of E-SAIL shall be capable of performing correctly in a wide range of different orbit inclinations (from equatorial to polar), local ascending node times and at various altitudes in LEO. This presents an additional challenge beyond a typical ADCS design, which can take advantage of a priori orbit configuration knowledge to optimise HW selection and attitude profile. For ESAIL, the design must be sufficiently generic to handle this substantial orbit uncertainty. In nominal mode, the ADCS shall point the instrument to nadir whilst also ensuring sufficient power is generated. In safe mode, sufficient power shall be guaranteed but actuation is limited to magnetorquers. The main findings in this paper cover the following aspects: (i) mode architecture definition and hardware selection, (ii) normal mode attitude guidance algorithm definition with derivation of the closed-form expression for the angular rate guidance, (iii) definition of a unique robust safe mode control law, considering the satellite structure and different orbits; the objective of the latter is to spin stabilize the spacecraft about the solar-panel long axis and then precess that away from the Sun when the spin vector gets too close.