Martin Stelzer

Robust and modular on-board architecture for future robotic spacecraft

This paper presents a novel approach for future robotic spacecraft by utilizing a modular and robust software architecture based on the time and space partitioning (TSP) concept. Classic satellites are characterized by a strict separation between platform and payload subsystems, both in hardware resources as well as in control software. Novel space-robotic applications such as on-orbit servicing (OOS) feature dexterous robotic devices attached onto the satellite that impose a direct physical feedback on their floating base. Through the high degree of interdependencies, the whole satellite turns into a space robot. Hence, the robot becomes an integral part of the spacecraft itself and needs to be integrated into the existing control and operations approach. The developed embedded on-board framework represents a modular and robust control and communication environment that allows both classic satellite as well as real-time and autonomous robotic operations. The framework features an integral fault detection, isolation and recovery (FDIR) concept in order to prevent overall system shutdown upon single-point failure. Single software components reside in separate logical modules, i.e. partitions, in order to avoid resource violations. Upon critical failure, partitions can be restarted without detracting the rest of the system. By applying explicit time scheduling of partitions, system resources can be optimally distributed and deterministic behavior be achieved. Core system functionality has been implemented by ECSS-tested components that are configurable and thus re-usable over multiple missions. As demonstrator, a realistic on-orbit servicing simulation was set up that comprises autonomous target satellite capture and fault management. The presented architecture follows an integrated approach that is required for safely operating future robotic spacecraft. Through re-usability of software components, fewer resources for the implementation and verification process are required as only additional, mission-specific components need to be taken care of. Application developers can use the core functionality and communication API and concentrate on their own task at hand.

MISSION CONTROL CONCEPTS FOR ROBOTIC OPERATIONS (MICCRO)

This paper gives an overview of the concept developed within the study “Mission Control Concepts for Robotic Operations (MICCRO)” aiming to find a representative mission control concept for robotic space missions. After presenting these conceptual ideas developed in project phase I, the design, planned utilization and current integration status of a demonstration prototype developed in project phase II to verify the concept in a realistic setup is explained. This end-to-end system based on an on orbit servicing scenario is under integration at the German Aerospace Center (DLR) in Oberpfaffenhofen, Germany. Using this facility, aspects like the handovers between mission phases and consequence on roles and responsibilities can be assessed. A particular emphasis is also put on new functional components like operator support functions on ground or an integrated Mission Control System (MCS) for the satellite platform and the robot in space.

Software architecture and design of the Kontur-2 mission

This paper describes the software architecture and design of the space segment, communication and ground segment software of the Kontur-2 project, which aimed to study the feasibility of planetary exploration through telepresence. The main research objectives in Kontur-2 were the development and in-flight verification of a space qualified two degree of freedom (DoF) force-feedback joystick (RJo) inside the Zvezda Service Module of the International Space Station (ISS), the implementation of telepresence technologies, and the study of human performance when controlling a force feedback joystick in microgravity. The project was conducted from 2012 to 2015 by a consortium consisting of the German Aerospace Center (DLR), the Russian Federal Space Agency (ROSCOSMOS), The Russian State Scientific Center for Robotics and Technical Cybernetics (RTC), S. P. Korolev Rocket and Space Corporation Energia (RSC “Energia”) and the Yuri A. Gagarin State Scientific Research-and-Testing Cosmonaut Training Center (GCTC). DLR conducted two sets of experiments in which a cosmonaut on board the ISS used RJo to perform different tasks with robots located on-ground. The first was conducted with a 2-DoF robot equipped with a camera system, a task board and torque sensors that allowed the cosmonaut to perceive reactive forces caused by contacts with the environment. For the second set of experiments a humanoid robot was utilized to perform a tele-handshake, as well as a cooperative task between the cosmonaut on ISS and colleagues at RTC in St. Petersburg. To realize these experiments, the consortium developed onboard and on-ground software which are described in this paper. The space segment software consists of the control software for RJo and user interfaces on a laptop to guide the cosmonaut efficiently through the experiments. A state machine was designed for these user interfaces to capture state changes during the experiment execution. This way only relevant contextual information is provided to the cosmonaut. On RJo, a component framework has been deployed combining a data-centric architecture with a CCSDS Space Packet interface. Additionally, the communication software has been designed to support a direct multi-channel connection between ground control and ISS using the S-band radio equipment of the consortium. During contact to ISS, the ground operators used the ground segment software at DLR for experiment support, supervision, maintenance and data logging. The visual feedback from the camera system required by the cosmonaut to perform the experiments was provided by a low-latency video stream through a communication channel with very restricted bandwidth. 23 experiment sessions were carried out in 2015 utilizing the Kontur-2 software, which helped to validate telepresence technologies and study human factors for space applications.