How NASA controls traffic around Mars

Chuck Bednar for redOrbit.com – @BednarChuck

With the addition of NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) and India’s Mars Orbiter Mission last year, there are now five spacecraft in orbit around the Red Planet. So just how does the US space agency keep those probes from crashing into each other?

The answer, according to NASA’s Jet Propulsion Laboratory, is a recently-upgraded collision-avoidance process that keeps tabs on both of those new arrivals, the ESA’s 2003 Mars Express orbiter, NASA’s 2001 Mars Odyssey and 2006 Mars Reconnaissance Orbiter (MRO), and even the agency’s no-longer-operational 1997 Mars Global Surveyor spacecraft.

This enhanced air traffic control system warns if two of those orbiters could potentially come too close to one another. It uses a process combining monitoring traffic, communicating, and planning evasive maneuvers to ensure that each orbiter maintains a safe distance from the others.

What if they collide?

One of the main factors that the agency has to take into consideration is the type of orbit used by each of the different probes to achieve their science goals. MAVEN, for example, analyses Mars’ upper atmosphere and flies an elongated orbit that alternately takes it further from and closer to the planet than other orbiters, meaning that it crosses their paths from time to time.

“Previously, collision avoidance was coordinated between the Odyssey and MRO navigation teams,” explained Robert Shotwell, Mars Program chief engineer at JPL. ‘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,” he added. While managing traffic above the Red Planet is less complex than it is here on Earth, where more than 1,000 active satellites and countless inactive ones in orbit, NASA officials are nonetheless taking precautions.

All five active Mars orbiters utilize the communication and tracking services of NASA’s Deep Space Network, which compiles trajectory information and allows engineers to make computer simulations of future trajectories up to a few weeks down the road. This lets them anticipate if and when traffic over the Red Planet will get heavy.

In cases where an avoidance maneuver proves necessary, NASA personnel would write, test, and approve commands for the spacecraft. Those instructions would only be sent, however, if models one or two days ahead indicated the possibility of a collision. Basically, the advanced warning system alerts the agency to a possible incident, allowing them to use higher-level monitoring to keep tabs on the situation and to begin discussing potential avoidance options.

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