NASA has lost touch with the first mini-spacecraft that ventured into deep space, according to the US space agency which said that it is unlikely the twin CubeSats will be heard from again. The MarCO CubeSats were launched last year to test if such low-cost technology can operate in deep space.
The twins, nicknamed EVE and WALL-E after characters from a Pixar film, served as communications relays during the InSight's Mars landing, beaming back data at each stage of its descent to the Martian surface in near-real time, along with InSight's first image.
WALL-E sent back stunning images of Mars as well, while EVE performed some simple radio science.
Having travelled well past Mars, the twin CubeSats seem to have reached their limit, NASA said in a statement.
It has been over a month since engineers have heard from MarCO, which followed NASA's InSight to the Red Planet. At this time, the mission team considers it unlikely they will be heard from again.
The experimental technology cost a fraction of what most space missions do -- USD 18.5 million.
WALL-E was last heard from on December 29 and EVE, on January 4. Based on trajectory calculations, WALL-E is currently more than 1.6 million kilometers past Mars; EVE is farther, almost 3.2 million kilometres past Mars.
The mission team has several theories for why they have not been able to contact the pair. WALL-E has a leaky thruster.
Attitude-control issues could be causing them to wobble and lose the ability to send and receive commands. The brightness sensors that allow the CubeSats to stay pointed at the Sun and recharge their batteries could be another factor.
The MarCOs are in orbit around the Sun and will only get farther away as February wears on. The farther they are, the more precisely they need to point their antennas to communicate with Earth.
The MarCOs will not start moving toward the Sun again until this summer. The team will reattempt to contact the CubeSats at that time, though whether their batteries and other parts will last that long cannot be predicted.
Even if they are never revived, the team considers MarCO a spectacular success.
"This mission was always about pushing the limits of miniaturised technology and seeing just how far it could take us," said Andy Klesh, the mission's chief engineer at JPL.
"We've put a stake in the ground. Future CubeSats might go even farther," Klesh said.
A number of critical spare parts for each MarCO will be used in other CubeSat missions. That includes their experimental radios, antennas and propulsion systems.
Several of these systems were provided by commercial vendors, making it easier for other CubeSats to use them as well.