For decades, a satellite in orbit was treated as untouchable. When it ran out of propellant or a component failed, the mission was over. In-orbit servicing is changing that. Spacecraft that can dock with other satellites to extend their life, repair them or move them are becoming part of the space logistics landscape.
The Hubble precedent
The Hubble Space Telescope is the best known example of servicing in orbit. Astronauts visited it on five Space Shuttle missions between 1993 and 2009 to repair it, replace instruments and upgrade its systems. These missions turned a telescope with a flawed mirror into one of the most productive observatories in history. The cover image shows Hubble during the rendezvous of the final servicing mission, STS-125.
Life extension for commercial satellites
Robotic servicing has since become a commercial reality. Northrop Grumman's Mission Extension Vehicles docked with the Intelsat 901 satellite in 2020 and with Intelsat 10-02 in 2021. The docked vehicle takes over propulsion and attitude control, which allows the satellite to keep operating after its own propellant would have run out.
Types of in-orbit services
- Life extension: a servicer docks and provides propulsion.
- Refuelling: propellant is transferred to a satellite that was designed with a suitable interface.
- Inspection: a servicer approaches another spacecraft to take images and assess its condition.
- Relocation and removal: satellites or debris are moved to other orbits or deorbited.
- Assembly and manufacturing: structures are built in orbit that could not be launched in one piece.
Challenges
Most satellites in orbit today were not designed to be serviced. They have no docking fixtures or refuelling ports, which makes capture and propellant transfer difficult. Rendezvous close to another operator's satellite also raises questions of safety, insurance and international coordination. Standardised interfaces for docking and refuelling are therefore an important development area.
What it means for new satellites
Operators designing satellites today can add simple features such as docking plates or markers for visual navigation at low cost. They keep options open for life extension or removal later and can support compliance with debris mitigation rules.
Related reading
- Swift Boost Mission Ends Without Reboost: Lessons for In-Space Servicing
- Space Tugs Explained: How Orbital Transfer Vehicles Deliver Satellites
- Satellite End of Life: Deorbiting, Graveyard Orbits and Passivation
Sources
- NASA: Missions to Hubble
- NASA Small Spacecraft Systems Virtual Institute: State of the Art of Small Spacecraft Technology
- Intelsat: Northrop Grumman and Intelsat Make History with Docking of Second Mission Extension Vehicle
Cover image: The Hubble Space Telescope during rendezvous with Space Shuttle Atlantis on STS-125, 2009. Credit: NASA (s125e006948), public domain.