How NASA got two robots to talk to each other on Mars

Vandana Verma remembers seeing the picture of the Perseverance rover and its smaller companion, the Ingenuity helicopter, on the Martian surface for the first time — a little family photo of two robots on another world.

“That was really, really exciting,” Verma, the chief engineer for robotic operations for the Perseverance rover, tells Inverse. “Having Ingenuity and Perseverance in the same image captures that special aspect of Perseverance because for the first time there’s a rover and a helicopter together on Mars.”

The two robots not only share a mission, but they also use the same phone line to Earth.

How do Ingenuity and Perseverance communicate with each other?

In order to communicate with mission control, Ingenuity needs Perseverance to deliver its messages. The helicopter and the rover use shiny little antennas to exchange data at about 100 kilobits per second, which is then routed from the Ingenuity-facing antenna to the rover’s main computer before being transferred to Earth via an orbiting spacecraft and an array of giant radio antennas.

Communicating to a planet located 33.9 million miles away is already tough enough, and Perseverance now has to add a little friend to the group chat. But this pair makes it look easy.

NASA’s Perseverance rover landed on Mars on February 18 with the quest to find ancient microbial life on the Red Planet and uncover its possibly habitable past.

READ MORE PERSEVERANCE ROVER NEWS FROM INVERSE

Perseverance follows in the wheel tracks of four other rovers previously sent to Mars, but this mission had an added feature — a 19-inch tall, 4-pound heavy helicopter that has already made history by being the first to take flight on another planet.

Ingenuity spent the journey to Mars tucked inside the rover. But after spending a month on Mars, the helicopter unpacked its tiny legs and stood up on its own on the Martian surface.

The two will slowly get further and further apart — possibly up to just under a mile, but still talking back and forth. The two robots will stay in touch with special antennas built in to facilitate communication between the helicopter team on the ground and the helicopter on Mars.

How does Ingenuity communicate with Earth?

Joshua Ravich, Ingenuity's mechanical engineering lead at NASA’s Jet Propulsion Laboratory, explains that the process begins by planning the helicopter’s tasks on Earth so it can perform those tasks autonomously on Mars.

“Ingenuity has a little gold-colored antenna that lives in it,” Ravich tells Inverse. “Data from Ingenuity goes through that antenna, and talks to the helicopter antenna that lives in the rover and that’s how it transfers data.”

Sounds simple enough, just like two robots with walkie-talkies on another planet talking to each other, but there’s more to making this slightly eerie sci-fi idea come to life.

The operations team puts together the plan for the day for both Perseverance and Ingenuity, sending out a set of commands that the two robots follow on Mars. That information gets sent through the Deep Space Network (DSN), which is NASA’s interplanetary communications network or a way for the space agency to make very, very long-distance calls.

The DSN uses radio frequency transmissions that travel through large antenna systems with specialized receivers. The network is made up of three deep-space communications facilities in three different locations across the world, which are strategically placed approximately 120 degrees apart. One facility is located at Goldstone, in California's Mojave Desert, another is near Madrid, Spain, and the third is near Canberra, Australia.

The reason behind this placement is to ensure that at any point in time, one or more of these complexes can communicate with the spacecraft as the Earth rotates around its 360-degree axis.

For Perseverance to reach DSN, it uses the Mars Relay Network. This is a fleet of orbiters including the Mars Reconnaissance Orbiter, Mars Odyssey, MAVEN, and two ESA missions: the ExoMars Trace Gas Orbiter (TGO) and Mars Express.

These spacecraft are all currently in orbit around Mars and facilitate the transfer of data between Earth and Perseverance.

As the information reaches Perseverance, it goes to the rover’s helicopter base station. The helicopter base station is an electronics assembly that lives on Perseverance and has its own antenna that communicates directly to Ingenuity.

The information then goes from Perseverance’s base station to the antenna on Ingenuity.

“And then Ingenuity wakes up and performs its tasks, lands, and it transmits data back in the reverse direction,” Ravich says.

Easy peasy.

Have two robots communicated before on Mars?

The only other time two robots landed on Mars and needed to communicate with one another was in 1997 when Sojourner, the first rover to operate on Mars, and Pathfinder, the spacecraft that landed with it, briefly transmitted data before parting ways on the Red Planet.

It will be the same case with Ingenuity and Perseverance. Their time together is limited by the lifetime of the helicopter. When its mission ends, whenever that is, the Perseverance rover will keep looking for signs of ancient life on Mars.

"That's a little up in the air, what the last flight might look like for Ingenuity and what its plans are, but ultimately we'll probably end up wherever we end up and Perseverance will go on with its mission," Ravich says.