Precision Orbit Control of the Advanced Land Observing Satellite (ALOS) for SAR Interferometry

Abstract

Earth observation satellites are typically inserted into orbits which rendezvous with ideal target orbits and are precisely controlled to form and maintain formations with virtual spacecraft on the ideal orbits. As Earth observing instruments achieve higher spatial resolution, their subsatellite cross-track deviation requirements become more stringent, and a new application by SAR interferometry requires a further improvement in orbit control accuracy. The Advanced Land Observing Satellite (ALOS), which was launched on January 24, 2006 and has been operated successfully on orbit, required precision orbit control for high-resolution Earth observation and SAR interferometry under various practical constraints. This paper presents the ALOS orbit control strategy with a particular emphasis on requirements and practical constraints, and demonstrates the resulting on-orbit performance in which equator crossing points have been regulated within ±0.5 km from reference ground paths, and altitude variations over the same geo-locations have been kept within ±0.5 km.