What's Next For Tiny Satellites?

Dec 27, 2018
Originally published on March 25, 2019 3:36 pm

NASA tried a communications experiment with its latest mission to Mars, and it turned out spectacularly well.

On Nov. 26, as the probe known as InSight plummeted through the Martian atmosphere on its way to the planet's surface, two miniature spacecraft — known collectively as MarCO — relayed telemetry from InSight to Earth, assuring all those watching that the landing of the probe was proceeding successfully and was soft.

In the past, spacecraft were only able to transmit back to Earth simple tones during a landing. Those tones would change for major milestones, such as parachute deployment, the firing of landing rockets or touchdown.

This time, as InSight team member Christine Szalai called out altitudes from the control room in the Jet Propulsion Laboratory in Pasadena, she was reading off actual data from InSight's onboard radar. It was live play-by-play, bearing in mind that the radio signal from Mars took approximately eight minutes to reach Earth.

The MarCO spacecraft are what are known as cubsesats. These are standardized minispacecraft. The cubesat model first appeared in 1999, as part of a program aimed at making it easier for university students to get projects into space.

The original cubesat was just 4 inches on a side, and weighed less than 3 pounds. Later versions allowed multiples of the original dimensions. The MarCOs are the size of six of the original cubesats stacked together.

NASA initially was interested in cubesats for their educational value, but the space agency has begun to see them as more broadly valuable.

"MarCO was primarily a technology demonstration," explains JPL mission engineer Anne Marinan. "There were brand new components and technologies that we flew for the very first time in deep space."

The MarCO satellites use a new kind of antenna to help a low-powered radio signal reach the Deep Space Network antennas back on Earth. They also rely on a new kind of propulsion system.

Marinan says the new technology hasn't always worked perfectly — one of the thrusters kept leaking, making the spacecraft hard to steer. But "it worked perfectly when it had to," she says.

The MarCOs and InSight left Earth on the same rocket last May. The two minisatellites then trailed close behind InSight on its way to Mars.

Marinan says the success of the MarCO in relaying InSight's signal may help make small, inexpensive satellites a regular partner of planetary landing missions.

After its relay mission was over, the MarCOs sailed past Mars; they'll go into orbit around the sun. Marinan says the research team on Earth will check in on the cubesats from time to time, just to see how long they last.

InSight, on the other hand, is just starting its mission to explore the interior of Mars. It's expected to operate on the Martian surface for about two Earth-years.

Marinan, who only recently earned her Ph.D., says MarCo was her first assignment at JPL. So, what do you do for an encore when your first mission worked so well?

"I am actually putting together another spacecraft," Marinan says. It's another miniature satellite, this time with its own science mission: to study a near-Earth asteroid.

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To another story now, two miniature spacecraft pulled off a remarkable feat last month. They provided live play-by-play as NASA's InSight probe made its successful touchdown on Mars. NPR's Joe Palca has the story of the two experimental mini-satellites known collectively as MarCO.

JOE PALCA, BYLINE: When InSight left Earth last May, NASA provided a familiar narration.


UNIDENTIFIED NASA EMPLOYEE: Five, four, three, two...

PALCA: Blastoff. Now, you expect to hear that. What's more unusual is this.


CHRISTINE SZALAI: Altitude 400 meters, 300 meters, 200 meters.

PALCA: That's Christine Szalai, a member of the InSight landing team at the Jet Propulsion Laboratory in Pasadena. She narrated InSight's descent from the control room at JPL.


SZALAI: Thirty meters, 20 meters, 17 meters.

PALCA: And then blastoff - I mean, touchdown.


SZALAI: Touchdown confirmed.


PALCA: Now, most of the time there is very little information coming back to Earth from a space probe as it comes in for a landing, maybe just a simple tone at key moments. And if there are any numbers, they're based on where mission controllers think the spacecraft should be based on a projected timeline. But the numbers Szalai was reading off were coming from InSight's onboard radar, actual data as it was coming in for landing.

Anne Marinan helped provide that data. She's an engineer at JPL who worked on MarCO. And she heard Szalai's narration.

ANNE MARINAN: She was doing it based on data that she was seeing that was transmitted from MarCO.

PALCA: How did that make you feel?

MARINAN: I didn't quite appreciate that that's what she was doing until I saw a rebroadcast. And it kind of hit me that she was able to make those calls based on data that my spacecraft had sent.

PALCA: MarCO is actually two briefcase-sized spacecraft that left Earth with InSight. The pair trailed close behind InSight on the way to Mars. InSight's radio couldn't reach Earth directly as it plummeted to the surface, but it could reach MarCO flying nearby. And MarCO's job was to relay back to mission control what InSight was sending. Marinan says the miniature satellite was an experiment.

MARINAN: MarCO was primarily a technology demonstration. So there were brand-new components and technologies that we flew for the very first time in deep space.

PALCA: A new kind of antenna, a new kind of propulsion. And Marinan says the new technology didn't always work perfectly. The propulsion system gave them headaches. But...

MARINAN: Well, it worked perfectly when it had to.

PALCA: This was Marinan's first assignment at JPL. She only recently earned her Ph.D. So what do you do for an encore when your first mission works so well?

MARINAN: I am actually currently putting together another spacecraft.

PALCA: Another miniature spacecraft, this one more science-y (ph), going to take pictures of a nearby asteroid. Joe Palca, NPR News.

(SOUNDBITE OF JOHN WILLIAMS' "CANTO BIGHT") Transcript provided by NPR, Copyright NPR.