The two MarCO CubeSats that accompanied NASA's InSight mission on its voyage to Mars have gone silent. Mission control has been unable to contact either of the briefcase-sized spacecraft for over a month as they continue to hurtle into deep space beyond the orbit of the Red Planet. The space agency says that it is highly unlikely that any more signals will be heard from them.

Though the loss of any deep space probe is a melancholy episode, the end of the MarCO mission is one that NASA is marking down as a complete success because their mere survival was pushing the envelope. The fact that both made a successful flyby of Mars and completed their assigned tasks was the icing on the cosmic cake.

MarCO-A and MarCO-B, nicknamed WALL-E and EVE, made history when they piggyback launched with the InSight probe last year to become the first deep-space CubeSats in history. Such miniature spacecraft have made great advances as engineers have learned how to use them either individually or in constellations to do the job of larger, more expensive satellites. However, until MarCO, these devices had been restricted to low-Earth orbit. No one was sure that such small, simple machines could stand up to the intense, hostile environment of interplanetary space.

Both US$18.5-million CubeSats performed above expectations. They trailed InSight and acted as an experimental direct communications relay with the lander as it descended to the Martian surface. In addition, WALL-E sent back images of Mars and Earth, showing the potential of such small, inexpensive craft.

According to NASA, communications were lost with WALL-E on December 29, 2018 and with EVE on January 4, 2019 as they journeyed to a distance of one million mi (1.6 million km) and two million mi (3.2 million km) beyond Mars, respectively. The reason for their going silent is unclear, but engineers believe that it could be due to attitude thruster malfunctions, the loss of the ability to orient themselves toward the Sun to charge their batteries, the difficulty of communicating over such distances, or some other system failure.

Though both spacecraft will return to the inner solar system in a few months, the space agency is not confident that they will remain active.

"This mission was always about pushing the limits of miniaturized technology and seeing just how far it could take us," says Andy Klesh, the mission's chief engineer at the Jet Propulsion Laboratory in Pasadena, California. "We've put a stake in the ground. Future CubeSats might go even farther."

Source: NASA

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