ESA GNC Conference Papers Repository

The International X-ray Observatory (IXO) is the next generation high energy telescope following on from XMM-Newton and Chandra. The objective of the IXO mission is to tackle some of the key questions in modern high energy astrophysics, with the following main science themes: Formation and Evolution of Galaxies, Clusters and Large Scale Structure, Black Holes and Matter Under Extreme Conditions, Life Cycles of Matter and Energy. The IXO mission concept is based on a single aperture telescope with a focal length of 20 m and six focal plane instruments, positioned at the focal point via a movable platform. The focal length is achieved via an Extendible Optical Bench with a deployed length of 12.5m. IXO will operate on a large amplitude halo orbit around the L2 co-linear libration point of the Sun/Earth-Moon system, which provides high observation efficiency with no eclipses, a very stable thermal environment and a relatively low radiation environment. The AMCS (Attitude Measurement & Control System), which is the AOCS system including the On-Board Metrology system (OBM) is at the heart of the Observatory’s capability to achieve the observation requirements and to meet the required image spatial quality and pointing capabilities with a large flexible structure. This paper identifies the IXO key design drivers to the AMCS design concept gathered around the following main topics: pointing requirements, observational requirement and in-orbit manoeuvres requirements. The paper then summarizes the AMCS architecture including: functional architecture and modes design, sensor and actuators selection and configuration. Whilst IXO was planned as a collaborative mission between international partners, ESA have initiated an Assessment Study for the complete mission design, focusing on a fully European mission (as far as possible). The IXO mission was a candidate large class mission for ESA’s Cosmic Vision 2015-2025 programme. A mission reformulation process has now started with the original IXO mission concept superseded. This paper presents the AMCS candidate architecture from the original mission concept which will be a good basis in the coming work to reformulate the IXO mission.