China is set to make history with its landmark orbital refuelling mission, Shijian-25, which aims to use a robotic arm to replenish the fuel of a fellow satellite, Shijian-21. The latter has run out of propellant since towing a defunct navigation satellite into a higher graveyard orbit in 2022.
However, what’s unusual is that two US spy satellites, USA 270 and USA 271, have positioned themselves nearby, flanking the Chinese satellites from east to west. According to a social media post by a space situational awareness company, COMSPOC, these satellites conducted multiple manoeuvres last week to achieve optimal viewing angles.
Harvard astronomer and space historian Jonathan McDowell described the behaviour of the American satellites as “highly uncommon”. This unusual observation has not been documented before, according to McDowell. On-orbit refuelling technology is considered crucial for extending satellite lifespans, reducing operational costs, and improving long-term sustainability in space.
The concept of on-orbit refuelling dates back to NASA’s 1960s plans, with the Defence Advanced Research Projects Agency (DARPA) successfully carrying out the Orbital Express mission in low Earth orbit in 2007. This technology has yet to be widely adopted but is expected to play a significant role in future space missions.
Source: https://www.scmp.com/news/china/science/article/3314364