Attitude determination and control system design for the CYGNSS microsatellite

This paper presents the development of the attitude determination and control system design of the Cyclone Global Navigation Satellite System spacecraft. The CYGNSS constellation consists of eight small satellite observatories in 500 km circular orbits at an inclination of 35 deg released from a single launch platform. Each CYGNSS spacecraft will make frequent and accurate measurements of ocean surface winds throughout the life cycle of tropical storms and hurricanes with the objective to fundamentally improve gap-free coverage for hurricane forecast and monitoring. Realising this objective requires the spacecraft to accurately and reliably point its signal collection antennae in desired directions and hold its Earth relative attitude over long time durations to prescribed knowledge and point requirements. Indeed, the microsatellite ADCS regulates all spacecraft estimation and control functionality spanning detumbling; Sun acquisition and hold; pointing control and momentum-management over the micro-satellite lifetime to design requirements. This paper presents the ADCS hardware, software and algorithms used to control the spacecraft in all phases of CYGNSS operations and presents simulation based performance results of the closed-loop estimation and control systems.