How space robotics extends our capabilities and insights
In August 2012, Voyager 1, a spacecraft launched by NASA in 1977, became the first human-made object to reach interstellar space. As of December 2021, Voyager 1 has been in service for more than 44 years, is 14.4bn miles from the sun, and travelling at more than 61,000kmh. If you’d like to check its progress today, the Voyager 1 mission log is still available here.
In another technological coup, NASA landed its Perseverance rover on a Martian river delta in February 2021. The robotic space mission is exploring the planet’s geology, searching for signs of ancient life, and drilling samples to be picked up by a later mission. It is also being used as a technology demonstrator for future robotic space missions, with features such as a ‘terrain relative navigation’ autopilot for avoiding hazards, an autonomous navigation system that will enable the rover to travel more quickly across difficult terrain, and a suite of sensors for gathering landing data.
Many of Perseverance’s functions rely on the use of radiation-hardened FPGAs. For example, Xilinx Virtex-5QV parts are used to implement the reprogrammable visual processor in the rover’s Computer Vision Accelerator Card, which handles stereo imaging tasks such as image rectification, filtering, detection, and matching. There are also Xilinx FPGAs in some of the mission’s instruments, such as the Mastcam-Z multispectral stereoscopic imager, and the SHERLOC spectrometer.
As the mission’s pièce de resistance, Perseverance carried a miniature helicopter in its belly. Ingenuity was designed to take off autonomously, fly up to 300m in Mars’ very thin atmosphere, and land, using a minimal set of commands sent from Earth in advance. The helicopter made the first of what was meant to be five test flights in April 2021, a short up-and-down ’hop’ to show that powered, controlled flight was possible on Mars.
As of December 2021, Ingenuity has made 17 flights, flown for more than 30 minutes, and travelled more than 3.5km across Mars’ surface at heights of up to 12m and speeds of 5m/s. The experimental helicopter, which some doubted would fly at all, is now firmly in operational mode, carrying out aerial scouting of nearby terrain to find sites of geologic interest. A planned 18th flight will push its technology even further, improving the robustness of communications with Perseverance so that Ingenuity can roam further from it. If communications are lost, the ground team is sanguine that the helicopter will land and wait until the rover comes close enough to re-establish line-of-sight communications.
Ingenuity (circled) photographed from Perseverance (NASA)
The utility and promise of space robotics
Engineers will applaud the phenomenal achievements that these and similar missions represent: partially or fully autonomous vehicles, some with robotic features, surviving in the harsh environment of space and operating far beyond their designed parameters and expected lifetimes. They should also applaud the implications of such robotic space missions, in helping us to understand the environment into which humans will eventually be launched, but at much lower cost and risk than would be involved using people.
Indeed, Michael Watkins, director of JPL, a key project partner, said when Perseverance landed: “We built the rover not just to land but to find and collect the best scientific samples for return to Earth, and its incredibly complex sampling system and autonomy not only enable that mission, they set the stage for future robotic and crewed missions.”
The UK’s Robotics & Autonomous Systems (RAS) Network made a similar point when it formalised its reasons for engaging with space robotics in a 2016 report. It said that “the technical goals of RAS are to extend human’s reach or access into space, expand our abilities to manipulate assets and resources, prepare them for human arrival, support human crews in their space operations, support the assets they leave behind, and enhance efficiencies of mission operations across the board.”
The resultant technologies should reduce the cost and risk involved in tasks such as refuelling missions, deploying and repairing satellites, assembling habitats and scientific instruments in space, and capturing and returning asteroids. Robotics will also make it easier to deploy planetary observers to survey extra-terrestrial surfaces. Increasing levels of autonomy in space missions should also reduce the cognitive load on astronauts already operating in challenging environments.
The technological evolution of space robotics
As robotic space missions become more complex, the enabling technology will have to evolve, with more advanced handling systems, and steadily increasing levels of autonomy. Take the landing of the Perseverance rover. As the craft entered Mars’ atmosphere, it was slowed by a parachute, and then separated from its heat shield and a protective shell. The resultant ‘sky crane’ then did a powered descent to a short distance above the planet, where it hovered while winching the rover down to the surface. Speed-of-light communications lag would have made this complex process impossible to control from Earth – Perseverance was on its own.
Space robotics systems, therefore, will have to evolve in stages from (remote) teleoperation, through automatic operation, to semi- and then fully autonomous operation. This will demand advances in robotic sensing and perception, mobility and manipulation, rendezvous and docking, onboard and ground-based autonomy systems, and greater human/robot integration.
This table from the 2016 RAS report summarises its view of how space robotics technology needs to evolve.
NASA has moved beyond producing technology roadmaps for its future missions, and in 2020 produced a technology taxonomy (below) instead. It shows the breadth of technology NASA believes it will need in future.
As TX04.4 and its subsections on human-robot interaction show, the future of space robotics systems will demand much more effective ways for people to work with robots, either directly, though online collaboration, or fully remotely. Some predict that the most intelligent and autonomous space robotics systems will evolve into roles as assistants to human astronauts.
NASA’s 2020 technology taxonomy for space robotic systems (NASA)
Robotics in orbit
There have already been some striking examples of human/robotic collaboration in space, such as Canadarm, a remote manipulator developed by the Canadian Space Agency and used aboard multiple space shuttle missions and on the International Space Station (ISS). The first generation of the arm, which went into service in 1981 and flew 90 times before it was retired in 2011, was used to help unload various payloads from the shuttle’s cargo area, rescue, and repair multiple satellites, and deploy the Hubble Space Telescope. Canadarm was also used as a work platform during extravehicular activities by astronauts who strapped their feet to a platform at the end of the arm and then were manipulated into their work positions.
Canadarm2 was mounted to the International Space Station in 2001 and has been used since to help with station maintenance, move supplies, equipment, and astronauts, and ‘catch’ unpiloted resupply ships arriving from Earth. These have included Northrup Grumman’s Cygnus vehicle, the Japanese Aerospace Exploration Agency’s H-II Transfer Vehicle, and more recently, SpaceX’s Dragon.
Canadarm2 is also used as a platform for Dextre, a ‘robotic handyman’ which does routine or difficult maintenance work on the ISS, freeing astronauts to spend their time on scientific experiments. Dextre has been in service since 2008, is 3.7m by 2.37m, has two 3.51m long arms with seven joints each, and weighs 1.7 tonne. The hand on each arm has a sense of touch, a motorised wrench, cameras and lights, and a retractable connector for power, data, and video hook-ups. It is used to install and replace small equipment on the ISS, such as exterior cameras and battery packs, as well as to carry out small repairs. In 2011, Dexter was upgraded so it could be used to explore techniques for servicing and refuelling satellites in orbit, gaining tools that could manipulate insulating blankets, cut wires, remove safety caps and more.
In subsequent robotic repair missions, NASA and partners have continued to develop robotic repair capabilities. In October 2020, both hands of Dextre were used at once to connect a 3.35m long hose to a port on a practice jig mounted on the ISS. A second robot – VIPIR2, the Visual Inspection Poseable Invertebrate Robot 2 – later used a snake-like borescope camera to check that the hose had been correctly connected.
In July 2021, the ISS gained another manipulator when the European Robotic Arm was deployed on the Russian segment of the ISS. This 11.3m-long arm has a reach of 9.7m, seven degrees of freedom, can manipulate masses of up to 8000kg, and position the tip of its manipulator with an accuracy of +/–5mm. The carbon fibre and aluminium arm can move itself hand-over-hand around the Russian section of the ISS so it is in position to handle tasks such as installing and removing experiments, transferring small payloads into the ISS through the Russian airlock, inspecting the outside of station, and moving crew between worksites.
The European Robotic Arm (Image © ESA)
Space clean-up
The increasing use of space, especially the recent launch of large constellations of communications satellites into low-earth orbit (LEO) will create demand for robotic rescue and repair missions. It will also create demand for the space equivalent of earth-bound sanitation crews, who can clean up space debris before it causes harm.
How bad is the issue? When Russia decided to test an anti-satellite weapon on one of its redundant satellites in November 2021, the resultant cloud of more than 1,500 pieces of trackable orbital debris and hundreds of thousands of smaller fragments forced astronauts aboard the ISS to take shelter for more than an hour. Debris in low-earth orbits can move at such high speeds that even very small particles can be a cause for concern.
The much more common source of space debris is from spent satellites and booster stages. Some satellite orbital positions, such as those that keep station above lucrative satellite TV markets, are both valuable and crowded. Satellite owners who use these slots are expected to be good citizens and clean up after themselves, either by shifting redundant satellites into a ’graveyard’ orbit or using their last remaining fuel to push them into burning up in Earth’s atmosphere.
Operators of satellites in other orbits may not want to deal with the costs of ‘de-orbiting’ their craft, and so we may have to develop active debris removal techniques using robotic space missions. The European Space Agency has already launched a Clean Space initiative, which includes guidelines for safe close-proximity operations in space. It has also made a deal with a Swiss start-up called ClearSpace to develop, launch and deploy ClearSpace-1. This ‘chaser’ robot will be launched into an orbit that matches that of a designated target and will then capture it with four robotic arms. The combined chaser and target will then be de-orbited to burn up in the atmosphere. In October 2021, the UK Space Agency signed a deal with ClearSpace to define a follow-on mission, in which a single chaser robot would remove multiple pieces of space debris from orbit.
The implications
Even as robots start being pressed into service to clean up space, other robots are being developed to extend humankind’s frontiers. For example, Perseverance has been diligently drilling into Mars’ surface and encapsulating the resultant material in sample tubes since it arrived on the planet. Meanwhile, NASA is already testing elements of the robotic systems which it hopes will one day fly to Mars to pick up those samples and return them to Earth. If this incredible feat of planning and engineering can be pulled off, then the steady evolution of space robotic missions will have reached another turning point.
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Paul Leys
Paul Leys is the Market Segment Manager for the Aerospace and Commercial Avionics business at Avnet ...
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