Mars' Orbiter Traffic Gets Busier with Five Spacecraft

Traffic around Mars is getting a bit busier. Last year's addition of two new spacecraft orbiting the Red Planet brought the total of active Mars orbiters to five, which is the most ever. Now, scientists are taking a closer look at these orbiters as collisions become a potential worry.

"Previously, collision avoidance was coordinated between the Odyssey and MRO navigation teams," said Robert Shotwell, one of the researchers, in a news release. "There was less of a possibility of an issue. MAVEN's highly elliptical orbit, crossing the altitudes of other orbits, changes the probability that someone will need to do a collision-avoidance maneuver. We track all the orbiters much more closely now. There's still a low probability of needing a maneuver, but it's something we need to manage."

Traffic management around Mars is far less complex than around Earth. More than 1,000 active orbiters plus addition pieces of inactive hardware orbit our planet. As Mars exploration intensifies, though, precautions may be needed in the future. There's now a new process to establish and manage this growth of orbiters as new members are added to the orbital community.

All five of the active Mars orbiters use the communication and tracking services of NASA's Deep Space Network. This brings trajectory information together, and engineers can run computer projections of future trajectories for comparisons.

"It's a monitoring function to anticipate when traffic will get heavy, said Joseph Guinn, manager of JPL's Mission Design and Navigation Section. "When two spacecraft are predicted to come too close to one another, we give people a heads-up in advance so the project teams can start coordinating about whether any maneuvers are needed."

The amount of uncertainty in the predicted Mars orbiter a few days ahead of time is more than a mile. And in most cases, calculating projections for weeks ahead multiplies the uncertainty to dozens of miles. However, the new formal collision-avoidance process for Mars helps scientists keep track of orbiters and watch them when two will be near one another. This is especially important as Mars' atmosphere becomes more crowded in years to come.

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