NASA has revealed it repurposed the processor the Perseverance rover used to communicate with the Ingenuity Mars Helicopter, to help the rolling robot navigate the Red Planet autonomously “for potentially unlimited distances.”
The aerospace agency revealed the hack last week in a post that says it used the rover’s Helicopter Base Station (HBS) because its processor is 100 times faster than the rover’s other kit.
NASA has previously said the HBS runs a Qualcomm 801 processor, a model the mobile chip giant lists as running four custom Krait CPUs using Arm-compatible cores of the company’s own design, an Adreno 330 GPU and a Hexagon digital signal processor. The Register’s coverage reports the models on Mars run at 2.26GHz and packs 2GB RAM plus 32GB flash memory, and that NASA ran Linux on the machine.
With Ingenuity now permanently grounded after flying 72 missions, the HBS was idle. The Jet Propulsion Laboratory’s chief engineer of robotics operations Vandi Verma therefore pondered reusing the hardware.
NASA calls the new workload it created for the SoC “Mars Global Localization” and in its post describes it as featuring “an algorithm that rapidly compares panoramic images from the rover’s navigation cameras with onboard orbital terrain maps.”
The agency says the algorithm “takes about two minutes to pinpoint the rover’s location within some 10 inches (25 centimeters)” and that it’s already in production, having been used on February 2nd and 16th.
“This is kind of like giving the rover GPS. Now it can determine its own location on Mars,” Verma wrote. “It means the rover will be able to drive for much longer distances autonomously, so we’ll explore more of the planet and get more science.”
NASA’s post says the software means “Perseverance can be commanded to drive to potentially unlimited distances without calling home.”
That’s a substantial improvement on the rover’s current autonomous navigational tools, which, the post explains, can see the robot become “increasingly unsure about its exact location” and sometimes get it wrong by up to 35 meters. “Believing it may be too close to hazardous terrain, Perseverance may prematurely end its drive and wait for instructions from Earth,” the post states.
“Tapping into the HBS computer has had its challenges,” NASA wrote, before explaining that it developed checks that see the algorithm run on the HBS multiple times before one of the rover’s main computers checks to ensure the results match.
“During testing, the team repeatedly found the rover’s position was off by 1 millimeter,” the post explains. “They discovered damage to about 25 bits – a minuscule fraction of the processor’s 1 gigabyte of memory – and developed a solution to isolate those bits while the algorithm runs.”
NASA appears to have been too modest to remind us that working on the rover can mean latency of up to 40 minutes, or that the fastest radio aboard Perseverance maxes out at 2 Mbps.
Verma thinks the work done to develop Mars Global Localization, and deploy it on the Snapdragon, will prove important as spacecraft designers use more commercial silicon. NASA’s post says its boffins have “already turned their sights to the Moon, where difficult lighting conditions and long, cold lunar nights make knowing exactly where spacecraft are located all the more critical.” ®