The Mars Cube One mission — the first to send CubeSats into interplanetary space — will test revolutionary relay technologies as it accompanies Mars Insight to the Red Planet.

Mars season is here. This summer sees the Red Planet make a fine opposition pass on July 31, 2018, one that's nearly as favorable as the historic opposition of 2003.

This alignment means it's the season for Mars-bound missions. NASA launched its Mars Insight mission on Saturday, May 5th — the only mission making the trip from Mars to Earth this season. But Mars Insight has company: twin Mars Cube One satellites launched with the larger mission.

The Mars Cube One mission is flying two separate spacecraft for redundancy. Both satellites successfully deployed from spring-loaded launchers located on the Centaur upper stage. MARCO-A was released shortly after Mars InSight separated from the Centaur upper stage booster, and MARCO-B followed A after the Centaur stage rotated 180 degrees.

"Both MarCO-A and B say 'Polo!'" said chief engineer Andy Klesh (NASA-JPL) in a press release. "It's a sign that the little sats are alive and well." Both CubeSats phoned home shortly after their release, indicating that their solar panels and communications antennae had deployed successfully.

The MARCO mission objective is a challenging one. The team will provide a dedicated relay during Mars InSight's descent to the surface of the Red Planet on November 26, 2018. Rather than entering orbit, the CubeSats will pass 2,175 miles (3,500 kilometers) from Mars during the larger mission's crucial landing phase. Mars will be 97.5 million miles (157 million kilometers) away at the time, making for an 8.7-light-minute communications lag from Mars to the Earth. The lag means that NASA engineers will need to wait 8.7 minutes to see whether the landing was successful, equivalent to Curiosity's "seven minutes of terror;" meanwhile, if all goes well, MARCO will have a front-row seat to the show. While the success of the InSight mission isn't dependent on MARCO, the CubeSats will provide a black box data recorder of all aspects of the mission's descent.

Data relay capability around the Red Planet is at a premium. The Mars Reconnaissance Orbiter (MRO) and Earthbound assets will be listening, though MRO will hold its data for about an hour before transmitting it to Earth. The worldwide Deep Space Network mainly listens for the “I'm alive" message as Mars InSight makes its way toward the surface. NASA also operates the aging Mars Odyssey mission, which has been active around Mars for an amazing 17 years. A roll call of active Mars orbiters also includes ESA's Mars Express and Trace Gas orbiter and India's Mars orbiter mission.

The MARCO CubeSats had their own dedicated clean room at the Jet Propulsion Laboratory (JPL) in Pasadena. The team informally nicknamed the pair Wall-E and Eva after the characters in Pixar's animated movie. Each spacecraft comes equipped with solar panels, cold gas thrusters, a large X-band antenna, and an ultra high-frequency receiver. The CubeSats will listen to Mars InSight and transmit data back to Earth at 8 kilobits per second. Both spacecraft also have star trackers and wide and narrow-field cameras, so we may see some deployment images from the pair soon, as well as Mars flyby images come November.

Mars InSight is the first dedicated planetary geodesy mission, set to probe the interior of Mars from its Elysium Planitia landing site. In addition to being accompanied by the first pair of interplanetary CubeSats, this was also the first interplanetary mission to launch from Vandenberg Air Force Base, on the West Coast. The 4:05 a.m. (local time) launch proved to be quite a spectacle up and down the Californian coast.

CubeSats in Space

CubeSat technology has revolutionized the modern satellite industry, bringing the access price to low-Earth orbit within the budget of universities or even private individuals. Most CubeSats are built using off-the-shelf technology; some “phonesats” are even built around the Google Android operating system. The International Space Station routinely dispenses CubeSats using its robotic arm. India's PSLV rocket deployed a record-breaking 104 satellites in a single launch on February 14, 2017. But most CubeSats placed in low-Earth orbit have short lifetimes, based on limited battery power and low orbits susceptible to drag from Earth's atmosphere.

MARCO will carry CubeSat technology one step further by testing key technologies. "These are our scouts," Klesh explains. "Cubesats haven't had to survive the intense radiation of a trip to deep space before, or use propulsion to point there way towards Mars. We hope to blaze that trail."

Measuring 14.4 x 9.5 x 4.6 inches in their stowed configuration, MARCO-A and MARCO-B are roughly the size of a breadbox. If successful, we could see more lightweight CubeSat relays on interplanetary missions. For example, we have no relay network in place around Europa, Titan, or Venus — all potential targets for future planetary missions.

It'll be interesting to watch the performance of the intrepid Mars Cube One mission in the coming months, as Mars InSight approaches the Red Planet.