NEW YORK — As they move into their third year exploring the surface of Mars, NASA’s two resilient rovers are getting ready to start using the new computer upgrades they received in September to improve their ability to make autonomous decisions.

The multi-megabyte software upgrades installed last September included four new capabilities for the Spirit and Opportunity rovers. Opportunity and Spirit have both lasted far longer than expected, giving NASA the chance to field-test new capabilities useful to both the current and future Mars missions .

One new capability, known as the “auto-place,” capability enables the rovers to calculate the best targets on which to point their instruments. Previously, researchers would have to wait for images to be transmitted from a rover, command it to perhaps move a bit to line up just right, and then plan a course for the arm to follow to bring the instruments down.

“Auto-place tries to eliminate all that work,” said Khaled Ali, a software engineer at NASA’s Jet Propulsion Laboratory, Pasadena, Calif . “We just checked out the autonomous mode on that, and we should see some real benefits from that soon.”

Another new add, t he “visual target tracking” capability, enables the rovers to lock onto and keep recognizing a target as they move towards it, even if its appearance changes in size or angle as the rovers maneuver closer or run up a slope.

Ideally, the visual target tracking capability will combine with the auto-place feature for an ability dubbed “go and touch,” which will allow engineers on Earth to pick a target for the rover will drive up to and then place instruments on, Ali said.

The new onboard science capability, often simply dubbed “watch,” will help the rovers recognize dust devils and clouds, so they can take specific pictures for scientists, instead of endless, often unwanted, snapshots. Researchers expect “watch” will free up rover communication time for additional scientific investigations. “Dust devil season is starting up on Mars, so the onboard science capability should become very useful in the near future,” Ali said.

The final new capability, dubbed D*, helps the rovers maneuver around obstacles.

“You could drop them in a middle of a maze, and they would find their way out,” Ali said. “Still, ever since Spirit was severely hobbled, with one wheel not working anymore, it hasn’t really had the chance to use it. And the area Opportunity is in doesn’t present it with as many obstacles, so I’m not sure we’ll really ever get to make full use of D* with these rovers.”

While the upgrades were installed in September, NASA is still gradually testing them to make sure each one is safe for use. “I’m guessing it will take another couple of months,” Ali said.

Opportunity and Spirit both landed on the red planet a little more than three Earth years ago. Opportunity has been on Mars for 1,087 Martian days, or sols, which is 997 days longer than it was supposed to last, and has just logged more than 10 kilometers of travel. Spirit has lasted 1,107 sols and has logged about 6.9 kilometers .