A CubeSat at Mars

For space exploration, small is powerful.

On November 26, 2018, MarCO-B returned this color image of Mars (and its own high-gain antenna) as it flew past the planet at a distance of about 4,700 miles. (NASA / JPL)
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The photo itself is unremarkable, and tells us nothing about Mars we didn’t know already. Yet MarCO-B’s snapshot, taken a few days after Thanksgiving, is important—the first close-up of another planet taken by a CubeSat.

Over the past 15 years, nearly a thousand of these small, cheap, modular satellites have been launched into Earth orbit to take pictures, test technology, and perform other simple tasks. The twin MarCOs, A and B, have the distinction of being the first CubeSats sent to interplanetary space. They survived the 300-million-mile journey to Mars, and half the battle was won right there.

NASA wanted to know if the briefcase-size MarCOs could handle such a long journey, then play a significant role on arrival: relaying radio signals back to Earth from the Mars Insight lander as it made its way down to the planet’s surface. The CubeSats weren’t critical to the primary mission’s success; other spacecraft were stationed in Mars orbit to capture Insight’s data in case the MarCOs failed.

NASA and the Jet Propulsion Laboratory spent just $18.5 million—a relative pittance—on the two smallsats and took only 14 months to build them. Launched with Insight on an Atlas V rocket last May, the MarCOs separated from the larger spacecraft shortly after leaving Earth orbit, and made their own way to Mars. During the cruise, JPL tested all the functions required of an interplanetary spacecraft. A new, purpose-built radio called Iris was able to communicate with the dish antennas of the Deep Space Network, a first for such a compact device. “It worked great!” enthused John Baker, JPL’s program manager for small spacecraft.

So did the onboard navigation system (which was accurate to within a few hundred meters at a distance of 90 million miles) and MarCO’s propulsion system, which squirted cold, compressed gas—the same kind used in fire extinguishers—from eight thrusters. The only glitches were blurry photos from MarCO-A’s low-cost camera, and a leaky thruster on MarCO-B, which the team was able to work around. Space radiation turned out to be no problem; the onboard computer memory suffered not a single upset.

The success of MarCO bodes well for future planetary CubeSats of increasing sophistication. Their advent will be, says Baker, “like going from the age of the mainframe to the age of the laptop.” His group is building a number of advanced CubeSats to be deployed in the vicinity of Earth and the moon from NASA’s new Space Launch System rocket when it makes its debut in 2020. Also on that test flight will be an asteroid mission called NEA Scout, which will carry the first “science-grade” camera on a planetary CubeSat. (The cheap, 1.2-megapixel cameras on the MarCOs were “a last-minute add-on,” says Baker, included to verify that the high-gain antenna had unfolded properly.)

As for the MarCOs, their mission officially ended when Insight touched down on Mars. But, says Baker, the team is considering an asteroid fly-by as an encore, and is now looking for suitable targets—if NASA gives the okay.

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