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.