Mars Cube One (or MarCO) was a Mars flyby mission launched on 5 May 2018 alongside NASA’s InSight Mars lander mission.[5] It consisted of two nanospacecraft, MarCO-A and MarCO-B, that provided a real-time communications link to Earth for InSight during its entry, descent, and landing (EDL) on 26 November 2018 – when InSight was out of line of sight from the Earth.[6] Both spacecraft were 6U CubeSats, and the mission was a test of new miniaturized communications and navigation technologies. These were the first CubeSats to operate beyond Earth orbit, and aside from telecommunications they also tested CubeSats’ endurance in deep space. On 5 February 2019, NASA reported that both the CubeSats had gone silent by 5 January 2019, and are unlikely to be heard from again.[3] In August 2019, the CubeSats were honored for their role in the successful landing of the InSight lander on Mars.[7]
The InSight lander re-transmitted its telemetry data during the landing, which demonstrated the new relay system and technology for future use in missions to other Solar System bodies. This provided an alternative to the orbiters for relaying information and achieved a technology development threshold.
After the MarCO satellites went silent in January 2019, there was a chance that communications with the satellites could be reestablished in the second half of 2019 as the satellites moved into more favorable location in space. NASA launched a campaign to establish communication with the satellites in September 2019. The communication attempts were unsuccessful and in 2 February 2020 NASA announced Mars Cube One mission formally ended.[8]