Abstract

With the advances in Robotics, Automation and Autonomous Systems (RAAS), the horizon of space
exploration has grown, and there is a need to develop space-qualified intelligent robots for future missions. Building
upon the heritage of successful surface exploration rover and lander missions to the Moon, Mars and Asteroids, the
space community worldwide is now pushing the frontiers of in-orbit robotics. Doubtlessly, RAAS will facilitate a
range of manufacturing, assembly, servicing and active debris removal missions. Resources published by space
agencies and major companies worldwide clearly indicate that mankind will start witnessing in-orbit robotic
missions within the next decade. This includes but not limited to building modular Large-Aperture Space Telescopes
(LAST), synthetic aperture radar, radiofrequency antennas, in-space power generation stations, mobile servicing
stations for repairing and maintenance of satellites and possibly large-scale infrastructure for space tourism. Out of
the many potential missions RAAS could support, in-orbit robotic assembly and construction of LAST is gaining
more popularity with the intent to understand the rate of growth of the cosmos and also for Earth Observation (EO).
However, there are numerous technical challenges associated with assembling LAST in space, including its
manufacturing and stowing into current and planned launch vehicles. To address these issues, a segmented design
approach for LAST is considered in this paper; the modular mirror units will be robotically assembled in orbit. The
in-space assembly of a modular 25m LAST mission concept is presented using a five Degrees-of-Freedom End-
Over-End Walking Robot (E-Walker). The design and gait pattern of the E-Walker is introduced first. The key
mission requirements including the requirements for the Robotic System, Space Telescope and Assembly are
discussed along with the strategies for scheduling the assembly process. Four main mission scenarios, subcategorised
into eleven mission scenarios are discussed in detail with a maximum of four E-Walkers. A trade-off
analysis was conducted to identify feasible mission scenarios and inferences are drawn accordingly to the best
mission concept of operations (ConOps) to realise the assembly of the 25m LAST. The results are based on the
overall mission mass-power budget, cost, control and motion planning complexity for the different mission scenarios
addressed in this paper. This study is a stepping stone towards proving the feasibility of the E-Walker for assembling
LAST; such advancements in orbital robotics will prove advantageous for building and servicing other high-value
infrastructure in space.