To avoid this, Perseverance uses its Rover Collision Model flight software to check for incoming movement and laser firing and autonomously stop any activity before a possible collision. For the robotic arm collision check, Perseverance projects the next robotic arm movement into the future and checks to see if any point in that movement would collide with the rover’s body. If the predicted movement has no unexpected collisions, then it will allow the movement to begin. But sometimes, the robotic arm does need to be very close to the hardware or even touch other parts of the rover’s body, such as exchanging drill bits or caching samples during docking. The rover knows when contacts are intentional and allows them to happen. While Perseverance uses AEGIS to autonomously select onboard science targets, it uses the rover collision model to filter out any targets that might cause a collision, and then selects a target for SuperCam targeting.
Typically, the operations team sends commands to the rover once every solar day, and Perseverance needs to protect itself if some of those activities don’t go as planned. If the exercise encounters even a glitch, such as on the 374th solar day, the robotic arm could unexpectedly remain in front of the rover and touch the target. The next morning, in the continuation of the same program, a planned LIBS launch would be directed at a rock now blocked by the robotic arm. On the 375th solar day, this was gracefully avoided by the rover collision model.
Collision checking happens autonomously, so the operations team usually doesn’t follow any explicit instructions. Unless an action fails a collision check during the ground simulation and needs to be adjusted, the operations team may not even notice it. The rover collision model is one of the flight software modules designed and programmed by the mission team. As of its 460th solar day, the rover has performed more than 64,000 collision checks on Mars with no errors, reporting collisions where expected.
Right now, Perseverance has arrived at Hogwallow Flats. It’s about to check out more collisions as it conducts some exciting scientific investigations.