The Mobile Servicing System (MSS) is a complex robotic system used extensively in the assembly, inspection and maintenance of the International Space Station (ISS). With the ISS construction now complete, the focus of MSS operations has shifted from assembly support to external maintenance activities. In 2011, the MSS successfully completed its first two logistics and maintenance operations using the Dextre robot: the relocation of new ISS components, delivered by the Japanese H-II Transfer Vehicle, and the removal and replacement of a failed ISS power controller module. This paper describes the planning and execution of Dextre's first tele-robotic operations. It summarizes the significant technical challenges encountered and presents the operational techniques developed to overcome them. Ground-controlled operations are shown to be an effective method to maximize external maintenance capability, and therefore ISS lifetime, as well as on-orbit crew availability for science activities. It is found that components designed to be robotically-serviceable can frequently present unforeseen challenges, driving the need for flexible operational tools and techniques, such as the use of force/moment sensing and accommodation. As a result, the approach developed for Dextre lends itself readily to future ISS maintenance tasks, but also to more general robotics exploration and satelliteservicing missions.
The Canadian Mobile Servicing System (MSS) is a complex robotics system used extensively in the assembly, inspection and maintenance of the International Space Station (ISS). During MSS operations, robotics flight controllers on the ground continuously assist the ISS astronauts by conducting numerous real-time activities: They plan and monitor robotics operations, but also command several MSS functions from the ground. The Canadian contribution to the ISS program includes real-time mission control and engineering support from the Canadian Space Agency's (CSA) Space Operations Support Center (SOSC). The SOSC's Remote Multi-Purpose Support Room (RMPSR) began actively supporting MSS operations in June 2004. This paper describes how on-orbit experience and anomalies have shaped both the roles and responsibilities of ISS robotics flight controllers, and how this has impacted RMPSR requirements. The paper introduces the concept of operation behind the RMPSR and presents an overview of the commissioning activities leading to its direct involvement with on-orbit robotics operations. Robotics flight control activities carried out from the RMPSR, which have included support to eight ISS assembly missions, are summarized. The challenges associated with a flight control team separated by large distances are explored, together with the technical and operational measures taken to ensure that the robotics flight control team continued to carry its training, mission planning, and real-time execution functions as an integrated team. Operational experience from the past four years has shown that a gradual phasing-in of RMPSR operations, combined with regular participation in integrated simulations and tests, was critical to its successful realtime support of on-orbit activities.
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