NASA's Mars rovers have been one of the great scientific and space successes of the past two decades.
Four generations of rovers have traversed the red planet gathering scientific data, sending back evocative photographs, and surviving incredibly harsh conditions -- all using on-board computers less powerful than an iPhone 1. The latest rover, Perseverance, was launched on July 30, 2020, and engineers are already dreaming of a future generation of rovers.
While a major achievement, these missions have only scratched the surface (literally and figuratively) of the planet and its geology, geography, and atmosphere.
"The surface area of Mars is approximately the same as the total area of the land on Earth," said Masahiro (Hiro) Ono, group lead of the Robotic Surface Mobility Group at the NASA Jet Propulsion Laboratory (JPL) -- which has led all the Mars rover missions -- and one of the researchers who developed the software that allows the current rover to operate.
"Imagine, you're an alien and you know almost nothing about Earth, and you land on seven or eight points on Earth and drive a few hundred kilometers. Does that alien species know enough about Earth?" Ono asked. "No. If we want to represent the huge diversity of Mars we'll need more measurements on the ground, and the key is substantially extended distance, hopefully covering thousands of miles."
Travelling across Mars' diverse, treacherous terrain with limited computing power and a restricted energy diet -- only as much sun as the rover can capture and convert to power in a single Martian day, or sol -- is a huge challenge.
The first rover, Sojourner, covered 330 feet over 91 sols; the second, Spirit, travelled 4.8 miles in about five years; Opportunity, travelled 28 miles over 15 years; and Curiosity has travelled more than 12 miles since it landed in 2012.
"Our team is working on Mars robot autonomy to make future rovers more intelligent, to enhance safety, to improve productivity, and in particular to drive faster and farther," Ono said.
NEW HARDWARE, NEW POSSIBILITIES
The Perseverance rover, which launched this summer, computes using RAD 750s -- radiation-hardened single board computers manufactured by BAE Systems Electronics.
Future missions, however, would potentially use new high-performance, multi-core radiation hardened processors designed through the High Performance Spaceflight Computing (HPSC) project. (Qualcomm's Snapdragon processor is also being tested for missions.) These chips will provide about one hundred times the computational capacity of current flight processors using the same amount of power.
"All of the autonomy that you see on our latest Mars rover is largely human-in-the-loop" -- meaning it requires human interaction to operate, according to Chris Mattmann, the deputy chief technology and innovation officer at JPL. "Part of the reason for that is the limits of the processors that are running on them. One of the core missions for these new chips is to do deep learning and machine learning, like we do terrestrially, on board. What are the killer apps given that new computing environment?"
The Machine Learning-based Analytics for Autonomous Rover Systems (MAARS) program -- which started three years ago and will conclude this year -- encompasses a range of areas where artificial intelligence could be useful. The team presented results of the MAARS project at hIEEE Aerospace Conference in March 2020. The project was a finalist for the NASA Software Award.
"Terrestrial high performance computing has enabled incredible breakthroughs in autonomous vehicle navigation, machine learning, and data analysis for Earth-based applications," the team wrote in their IEEE paper. "The main roadblock to a Mars exploration rollout of such advances is that the best computers are on Earth, while the most valuable data is located on Mars."
Training machine learning models on the Maverick2 supercomputer at the Texas Advanced Computing Center (TACC), as well as on Amazon Web Services and JPL clusters, Ono, Mattmann and their team have been developing two novel capabilities for future Mars rovers, which they call Drive-By Science and Energy-Optimal Autonomous Navigation.
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