Space may be big, but in our neck of the woods it's getting crowded. There are thousands of active and inactive satellites in orbit around Earth, and while Mars may not exactly be Piccadilly Circus, it now has five active satellites circling it. To prevent any unfortunate collisions around the Red Planet, NASA is working on a new traffic management system.
With the arrival of NASA's Mars Atmosphere and Volatile Evolution (MAVEN) and India's Mars Orbiter Mission, Mars is becoming a busy interplanetary destination. In addition to the five active satellites, there's also the inactive NASA Mars Global Surveyor, plus a couple of natural moons, so the traffic situation is already becoming a bit tricky.
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According to NASA, this isn't simply a matter of extreme playing safe. The spacecraft circling Mars aren't just in the same neighborhood, they're also in similar intersecting orbits. The problem may be less complex than keeping thousands of Earth satellites out of one another's way, but it's also trickier when you consider that traffic control is hundreds of millions of miles from the task at hand.
It's also more than an abstract concern. NASA says that on January 3, there were worries that within two weeks the MAVEN and Mars Reconnaissance Orbiter (MRO) would pass within two miles (3 km) of one another. Later calculations indicated that this would not occur, but it highlights part of the problem. Earth satellites can be precisely tracked, but the ones around Mars are tracked using calculations and NASA's Deep Space Network (DSN). This allows for some very accurate work ups, but when dealing with future orbits involving five satellites, there is an element of uncertainty. This means that in future the Mars orbiters need much closer tracking, which is part of DSN's job, and which NASA's new traffic management system will be able to fine tune.
"It's a monitoring function to anticipate when traffic will get heavy," says Joseph Guinn, manager of Jet Propulsion Laboratory'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 idea is to maintain a close watch on the existing Mars orbiters and develop methods for expanding the system as more spacecraft arrive. This collision avoidance is part of NASA's Multi-Mission Automated Deep-Space Conjunction Assessment Process, and will allow the space agency to determine whether any future risks exist far enough in advance to communicate what may happen and for new command codes to be written and transmitted for correction maneuvers. NASA says that this improvement in traffic management will not only cut down on the danger of collisions, but also allow Mars orbiters to act more closely together to jointly study Martian phenomena.