Planetary Exploration requires Balancing Risk and Reward

Planetary Exploration requires Balancing Risk and Reward

Society demonstrates a willingness to tolerate high levels of risk for individuals who engage in certain types of activities. Every day, firefighters, law enforcement officers, other first responders, and military service members risk their lives and health in the defense of people, property, national security, or other compelling public interests. Researchers have devised a novel method for balancing the risks and scientific value of sending planetary rovers into perilous situations.

While traversing the Martian landscape, NASA’s Mars rovers strive for ground-breaking scientific discoveries. At the same time, the rovers’ crews do everything they can to protect them and the billions of dollars behind the mission. This balance between risk and reward drives the decisions surrounding where the rovers go, the paths they take to get there and the science they uncover.

The Robotics Institute (RI) at the School of Computer Science has developed a new approach to balancing the risks and scientific value of sending planetary rovers into dangerous situations.

David Wettergreen, a RI research professor, and Alberto Candela, who earned his Ph.D. in robotics and is now a data scientist at NASA’s Jet Propulsion Laboratory, will present their work, “An Approach to Science and Risk-Aware Planetary Rover Exploration,” later this month in Kyoto, Japan, at the IEEE and RSJ International Conference on Intelligent Robots and Systems.

Our goal is not to eliminate scientists, not to eliminate the person from the inquiry. Really, the point is to enable a robotic system to be more productive for scientists. Our goal is to collect more and better data for scientists to use in their investigations.

David Wettergreen

“We looked at how to balance the risk associated with going to challenging places against the value of what you might discover there,” said Wettergreen, who has worked on autonomous planetary exploration for decades at Carnegie Mellon University. “This is the next step in autonomous navigation and to producing more and better data to aid scientists.”

Wettergreen and Candela’s approach combines a model for estimating science value with a model for estimating risk. The robot’s confidence in its interpretation of rock mineral composition is used to calculate science value. If the robot believes it has correctly identified rocks without the need for additional measurements, it may choose to explore a new area. However, if the robot’s confidence is low, it may decide to continue studying the current area and improving its mineralogical model. Zo, a rover that has been testing autonomous technologies for decades, used an earlier version of this model during experiments in the Nevada desert in 2019.

The researchers determined risk through a model that uses the topography of the terrain and the terrain’s makeup material types to estimate how difficult it will be for the rover to reach a specific location. A steep hill with loose sand could doom a rover’s mission – a real concern on Mars. In 2004, NASA landed twin rovers, Spirit and Opportunity, on Mars. Spirit’s mission ended in 2009 when it became stuck in a sand dune and its wheels slipped when it tried to move. Opportunity carried on and worked until 2018.

Balancing risk and reward in planetary exploration

Wettergreen and Candela put their framework to the test with actual Mars surface data. The team used this data to send a simulated rover scurrying around Mars, charting different paths based on varying risk, and then evaluated the science gained from these missions.

“The rover performed admirably on its own,” Candela said of the simulated Mars missions. “Even in high-risk simulations, there were still plenty of areas for the rover to explore, and we discovered some interesting things.”

This study builds on decades of RI research into autonomous planetary exploration. Papers dating back to the 1980s propose and demonstrate methods for rovers to move autonomously across the surfaces of other planets, and technology developed as a result of this research has been used on recent Mars rovers.

CMU researchers proposed Ambler, a self-sufficient, six-legged robot that could prioritize its goals and chart its own path on places like Mars. In the early 1990s, the team tested the six-meter-tall robot. More rovers followed, including Ratler, Nomad, and Hyperion, a rover designed to travel in the direction of the sun to charge its batteries.

Zoë began its work in harsh environments in 2004 and has traveled hundreds of miles in Chile’s Atacama Desert, an environment in many ways similar to Mars. By 2012, Zoë’s missions in the desert shifted to focus on autonomous exploration and the decisions behind where to go and what samples to collect. A year later, the rover autonomously decided to drill into the desert soil, and it discovered what turned out to be unusual, highly specialized microbes, demonstrating that automated science can result in valuable discoveries.

Candela and Wettergreen plan to put their recent work on Zo to the test during a trip to the Utah desert. They also see their research as making significant contributions to future lunar exploration. Scientists could use their approach to investigate potential routes in advance and balance the risk of those routes with the science that could be gained. The method could also help a new generation of autonomous rovers sent to the surface of planets to conduct science experiments without constant human intervention. Before charting its own course, the rover could weigh the risks and benefits.

“Our goal is not to eliminate scientists, not to eliminate the person from the inquiry,” Wettergreen said. “Really, the point is to enable a robotic system to be more productive for scientists. Our goal is to collect more and better data for scientists to use in their investigations.”