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Part of NASA’s CADRE technology demonstration, three small rovers that will explore the Moon together show off their ability to drive as a team autonomously – without explicit commands from engineers – during a test in a clean room at the agency’s Jet Propulsion Laboratory in December 2023. Credit: NASA/JPL-Caltech
Construction and testing are complete on the CADRE rovers, which will map the lunar surface together as a tech demo to show the promise of multirobot missions.
A trio of small rovers that will explore the Moon in sync with one another are rolling toward launch. Engineers at NASA’s Jet Propulsion Laboratory in Southern California recently finished assembling the robots, then subjected them to a punishing series of tests to ensure they’ll survive their jarring rocket ride into space and their travels in the unforgiving lunar environment.
Part of a technology demonstration called CADRE (Cooperative Autonomous Distributed Robotic Exploration), each solar-powered rover is about the size of a carry-on suitcase. The rovers and associated hardware will be installed on a lander headed for the Moon’s Reiner Gamma region. They’ll spend the daylight hours of a lunar day – the equivalent of about 14 days on Earth – conducting experiments by autonomously exploring, mapping, and using ground-penetrating radar that will peer below the Moon’s surface.
The goal is to show that a group of robotic spacecraft can work together to accomplish tasks and record data as a team without explicit commands from mission controllers on Earth. If the project succeeds, future missions could include teams of robots spreading out to take simultaneous, distributed scientific measurements, potentially in support of astronauts.
Engineers have put in long hours test-driving rovers and working out bugs to finish the hardware, get it through testing, and prepare it for integration with the lander.
“We have been in overdrive getting this tech demo ready for its lunar adventure,” said Subha Comandur, CADRE project manager at JPL. “It’s been months of nearly round-the-clock testing and sometimes re-testing, but the team’s hard work is paying off. Now we know these rovers are ready to show what a team of little space robots can accomplish together.”
Shake and Bake
While the list of tests is extensive, the most brutal involve extreme environmental conditions to ensure the rovers can withstand the rigors of the road ahead. That includes being locked in a thermal vacuum chamber that simulates the airless conditions of space and its extreme hot and cold temperatures. The hardware also gets clamped to a special “shaker table” that vibrates intensely to make sure it will endure the journey out of Earth’s atmosphere.
“This is what we submit our rovers to: ‘shake’ to simulate the rocket launch itself and ‘bake’ to simulate the extreme temperatures of space. It’s very nerve-wracking to witness in person,” said JPL’s Guy Zohar, the project’s flight system manager. “We’re using many carefully selected commercial parts on our project. We expect them to work, but we’re always a little worried when we go into testing. Happily, each test has ultimately been successful.”
Engineers also performed environmental testing on three hardware elements mounted on the lander: a base station that the rovers will communicate with via mesh network radios, a camera that will provide a view of the rovers’ activities, and the deployer systems that will lower the rovers to the lunar surface via a fiber tether fed slowly out from a motorized spool.
Putting Code to the Test, Too
Meanwhile, engineers working on CADRE’s cooperative autonomy software have spent many days in JPL’s rocky, sandy Mars Yard with full-scale versions of the rovers called development models. With flight software and autonomy capabilities aboard, these test rovers showed they can accomplish key goals for the project. They drove together in formation. Faced with unexpected obstacles, they adjusted their plans as a group by sharing updated maps and replanning coordinated paths. And when one rover’s battery charge was low, the whole team paused so they could later continue together.
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