First uncrewed on-orbit satellite servicing

The first uncrewed spacecraft to restore the functionality of an inactive satellite is the Mission Extension Vehicle (MEV-1) built by US aerospace company Northrop Grumman and operated by its subsidiary SpaceLogistics. On 25 February 2020, the MEV-1 successfully grappled the inactive Intelsat 901 communications satellite, which had been retired to a graveyard orbit was it was running out of fuel for its attitude control thrusters. Once it was securely attached to Intelsat 901, the MEV-1 "space tug" was able to use its attitude control systems to steer the conjoined spacecraft, moving it back into geostationary orbit and returning it to active service on 2 April 2020.

The MEV-1 has a mass of 2,326 kg (4,929 lb) and was launched using a Russian Proton rocket on 9 October 2019. It is designed to have an operational lifespan of 15 years, and can dock and undock multiple times during this period. The contract with Intelsat with see the MEV-1 remain attached until 2025, at which time it will likely move the satellite back into a graveyard orbit before heading off to rendezvous with the next customer.

The MEV-1 is the first spacecraft created to dock with satellites that weren't designed with docking in mind. It attaches to its target using an extendable probe which enters the bell of the satellite's main rocket motor before clamping itself into place. As almost all satellites have a rocket motor that is used for manoeuvring and orbital insertion, this is a technique that can be used across a range of targets.

SpaceLogistics launched a second MEV on 15 August 2020. It docked with Intelsat 10-02 in geostationary orbit on 12 April 2021, and is set to extend the working life of the 17-year-old satellite by at least 5 years. NASA and its industry partners are currently working on systems that would make it possible to refuel spacecraft, rather than rely on fixed tugs.

Prior to the launch of the first MEV, the only on-orbit servicing missions had been undertaken by the human crew of the US Space Shuttle. The first was the repair of the Solar Maximum Mission satellite in 1984, followed by repairs to two commercial satellites (in 1985 and 1992) and the five Hubble Space Telescope service missions between 1993 and 2009.