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New 'Mars GPS' lets Perseverance pinpoint its location within 25 centimeters
by NASA
edited by Lisa Lock, reviewed by Andrew Zinin
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The Mars Global Localization algorithm runs on a fast commercial
processor in the Helicopter Base Station rCo the upper, gold-colored box
that was integrated into NASArCOs Perseverance rover in a clean room. Perseverance used the base station to communicate with the now-retired Ingenuity Mars Helicopter. Credit: NASA/JPL-Caltech
Imagine you're all alone, driving along in a rocky, unforgiving desert
with no roads, no map, no GPS, and no more than one phone call a day for someone to inform you exactly where you are. That's what NASA's
Perseverance rover has been experiencing since landing on Mars five
years ago. Though it carries time-tested tools for determining its
general location, the rover has needed operators on Earth to tell it
precisely where it isrCountil now.
A new technology developed at NASA's Jet Propulsion Laboratory in
Southern California enables Perseverance to figure out its whereabouts
without calling humans for help. Dubbed Mars Global Localization, the technology features an algorithm that rapidly compares panoramic images
from the rover's navigation cameras with onboard orbital terrain maps.
Running on a powerful processor that Perseverance originally used to communicate with the Ingenuity Mars Helicopter, the algorithm takes
about two minutes to pinpoint the rover's location within some 10 inches
(25 centimeters). Mars Global Localization was first used successfully
in regular mission operations on Feb. 2, then again Feb. 16.
"This is kind of like giving the rover GPS. Now it can determine its own location on Mars," said JPL's Vandi Verma, chief engineer of robotics operations for the mission. "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. And it could be used by almost any other
rover traveling fast and far."
The upgrade is especially valuable given how well Perseverance's auto-navigation self-driving system has been working. Enabling the rover
to re-plan its path around obstacles en route to a preestablished
destination, AutoNav has proved so capable that the distance
Perseverance can drive without instructions from Earth is largely
limited by the rover's uncertainty about its whereabouts. Now that it
can stop and determine its exact location, Perseverance can be commanded
to drive to potentially unlimited distances without calling home.
Implementation of Mars Global Localization comes on the heels of another innovation from the Perseverance team: the first use of generative
artificial intelligence to help plan a drive route by selecting
waypoints for the rover, which are normally chosen by human rover
operators. Both technologies enable Perseverance to travel farther and
faster while minimizing team workload.
Beyond visual odometry
Unlike on Earth, there is no network of GPS satellites in deep space to
locate spacecraft on planetary surfaces. So missionsrCowhether robotic or crewedrComust come up with other ways to determine their location.
As with NASA's previous Mars rovers, Perseverance tracks its position
using what's called visual odometry, analyzing geologic features in
camera images taken every few feet while accounting for wheel slippage.
But as tiny errors in the process add up over the course of each drive,
the rover becomes increasingly unsure about its exact location. On long drives, the rover's sense of its position can be off by more than 100
feet (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.
"Humans have to tell it, 'You're not lost, you're safe. Keep going,'"
Verma said. "We knew if we addressed this problem, the rover could
travel much farther every day."
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The new technology called Mars Global Localization enables NASArCOs Perseverance to pinpoint is location using an onboard algorithm that
matches terrain features in navigation camera shots (the circular image, called an orthomosaic) to those in orbital imagery (the background).
Credit: NASA/JPL-Caltech
After each drive comes to a halt, the rover sends a 360-degree panorama
to Earth, where mapping experts match the imagery with shots from NASA's
Mars Reconnaissance Orbiter (MRO). The team then sends the rover its
location and instructions for its next drive. That process can take a
day or more, but with Mars Global Localization, the rover is able to
compare the images itself, determine its location, and roll ahead on its preplanned route.
"We've given the rover a new ability," said Jeremy Nash, a JPL robotics engineer who led the team working on the project under Verma. "This has
been an open problem in robotics research for decades, and it's been
super exciting to deploy this solution in space for the first time."
The small team began working in 2023, testing the accuracy of the
algorithm they'd developed using data from 264 previous rover stops. The algorithm compared rover panoramic photos to MRO imagery and correctly pinpointed the rover's location for every single stop.
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How Ingenuity helped
Key to Mars Global Localization is the rover's Helicopter Base Station
(HBS), which Perseverance used to communicate with the now-retired
Ingenuity Mars Helicopter. Equipped with a commercial processor that
powered many consumer smartphones in the mid-2010s, the HBS runs more
than 100 times faster than the rover's two main computers, which, built
to survive the radiation-heavy Martian environment, are based on
hardware introduced in 1997.
This panorama from Perseverance is composed of five stereo pairs of
navigation camera images that the rover matched to orbital imagery in
order to pinpoint its position on Feb. 2, 2026, using a technology
called Mars Global Localization. Credit: NASA/JPL-Caltech
As a technology demonstration designed to test capabilities, the
Ingenuity mission was able to risk employing more powerful commercial
chips in the HBS and the helicopter even though they hadn't been proven
in space. It paid off: Expected to fly no more than five times, the
rotorcraft completed 72 flights.
The power of the HBS processor inspired Verma to look for ways the Perseverance mission might harness it. "It's almost like a gift.
Ingenuity blazed the trail, proving we could use commercial processors
on Mars," Verma said.
Tapping into the HBS computer has had its challenges. To address
reliability, the team developed a "sanity check": The algorithm runs 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. They discovered damage to
about 25 bitsrCoa minuscule fraction of the processor's 1 gigabyte of memoryrCoand developed a solution to isolate those bits while the
algorithm runs.
Alongside the broader Mars Global Localization process, the team's
sanity check and memory solutions are expected to find new uses as
faster commercial processors are employed in future missions. In the
meantime, the team has 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.
Key concepts
structure from motion
Provided by NASA
Explore further
Perseverance rover completes first AI-planned drive on Mars
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