Various space agencies periodically send “robots” and robotic vehicles to explore the moon, planets and other celestial bodies, in order to improve our understanding of the environment and resources in different parts of the solar system.
Recently, researchers from the University of Toronto’s Institute for Space Studies and NASA’s Jet Propulsion Laboratory conducted a study to explore strategies that could improve the effectiveness and success of lunar exploration using solar-powered vehicles.
Their paper, published on the Archive website – which is intended for the temporary publication of scientific research – presents a new approach that could help solar-powered vehicles safely leave the permanently shaded regions on the moon.
Risky bid
“In recent years, several countries have expressed interest in exploring the south pole of the Moon, including the United States, China, India, Russia, and others,” Olivier Lamarre, the researcher who led the study, tells Phys.org.
Solar-powered rovers can have many advantages in terms of energy efficiency, however they are limited by their dependence on sunlight to operate. Because some areas of the moon are permanently in shadow, the rover’s dependence on sunlight could prevent it from exploring these areas and then leaving safely, because they run out of energy during their mission.
The last of those vehicles that tried to land on the south pole of the moon – which is the always shaded side of the moon – was the Russian spacecraft “Luna 25”, which crashed on August 20, and it is already on its way to land, and what the vehicle was exposed to may be the same. Related to the problem of this type of space missions.
So the main goal of Lamarre et al.’s recent work was to quantify the potential for solar-powered vehicles to be lost as they explored these shadowed regions of the Moon. In addition, the team wanted to come up with an approach that could help make solar vehicles more likely to complete their missions safely.
refund policy
Lamarre explained that we first need to define what it means for a solar-powered rover to be safe at the lunar south pole, and to do that, we need to determine where the rover is in the lunar shadow region, what time it is in its mission, and how much power is left. in its batteries.
This gives an indication of the vehicle’s condition, and whether or not it will enter a hibernation state in place before the next phase of its mission. Then, the rover is planned online for steps to take to get through the situation it’s in, in order to increase the likelihood that it will stay operational.
The planning methodology outlined by Lamarre and colleagues is known as a recovery policy, as it is essentially a back-up strategy that allows the vehicle to maximize the chance of getting to “safety,” the areas where sunlight reaches, and thus the areas to recharge its battery. In their paper, the researchers show that calculating this refund policy can be challenging. Because it requires many approximations which, if incorrect, may affect the reliability of the overall predictions.
At the Moon’s south pole, solar illumination is very dynamic; Where nearby mountains and craters can cast large shadows on the surface, if the rover is a little behind schedule than the rough policy assumes, it could miss a critical solar charging period. The same is true if they are a little ahead of schedule than what the policy assumes.
Advantages of the refund policy
The proposed approach is beneficial in many ways from the researchers’ point of view. Because it represents a step towards having long-range mobility planning algorithms that proactively consider risks to solar-powered rovers.
In addition, the approach could become a useful tool for human operators as they formulate new lunar south pole rover missions, where it can be used to select a landing site, plan and forecast hazards, and more, or even to support an ongoing mission from Earth.
The approach was tested using orbital data from one of the lunar craters, and the team hopes to use NASA’s solar illumination maps, and then apply their technology to many other regions in the lunar south pole. The team is also working on equipping a new generation of long-range navigation algorithms to predict hazards. To explore the lunar south pole, using solar powered vehicles.
