ESA's XMM-Newton space observatory, the flagship of European X-ray astronomy, is after it's launch in 1999 the most powerful X-ray telescope ever placed in orbit. The mission originally designed for a 10 years lifetime is planned to be operated long into this decade since spacecraft and instruments are operating admirably without major degradation. Therefore recently a system called XMM Early Warning System (XEWS) is developed to perform near-real-time trend analysis of spacecraft parameters in order to detect early degradation of components. This will enable the mission to perform early counter measures in case degradation is detected. During the development of XEWS it has been spotted that one of XMM-Newton's reaction wheels shows since 2008 non-periodic friction increase during stable pointing. We present an analysis of all four reactions wheels since the start of the mission identifying the periods of increased friction and giving some possible causes and cures for this effect that is as well know as "cage instability" and describe the impact on operations. Additionally a comparison with the wheels of ESA's INTEGRAL spacecraft which is using effectively the same Attitude and Orbit Control System will be presented..

ESA's XMM-Newton space observatory launched in 1999, is the flagship of European Xray astronomy and the most powerful X-ray telescope ever placed in orbit. The mission, originally designed for a 10 years lifetime, is planned to be operated long into this decade since spacecraft and instruments are performing admirably without major degradation. The ultimate mission end of life was defined as 2019, limited by the hydrazine reserves on board. Since scientific demand on XMM-Newton is very high and the mission has been ranked top level by the ESA advisory structure, various options to reduce the fuel consumption have been investigated. Some of these have been put in place in the course of the last years, especially we have updated the on-board software of the Attitude Control Computer to allow operating all four reaction wheels in parallel instead of only running three of them as done previously. Simulations and experience from ESA's HERSCHEL mission have shown that this should reduce the fuel consumption by up to a factor of two. In addition, operating with four reaction wheels offers the possibility to apply some measures against increased bearing noise due to aging, which has been detected on two of the XMM-Newton reaction wheels. The usage of all fuel saving methods may extend the potential lifetime to 2030. We present the implementation and results of the applied fuel saving methods and describe the increased bearing noise and its mitigation measures. In addition will report on the outcome of relubrication exercises performed on two of the wheels to cure the increased bearing noise. Furthermore we describe plans that are currently developed to operate the Hydrazine Propulsion System in the so-called near fuel depletion regime at the end of the technical life limit. In addition, ground segment evolution related to hardware, software and automation possibilities facing the new very long term perspective are discribed.

No abstract

No abstract

No abstract