China Prepares for Historic Satellite Refuelling Test in Geostationary Orbit

China appears to be on the verge of achieving a landmark milestone in space technology — the world’s first satellite-to-satellite refuelling operation in geostationary orbit. On Monday, two Chinese spacecraft, Shijian-21 and Shijian-25, came into extremely close proximity, suggesting an imminent attempt at autonomous docking and fuel transfer.

According to Swiss space surveillance firm s2a Systems, the two satellites — orbiting at an altitude of 35,786 km (22,236 miles) above the equator — have been closing in on each other for days. New tracking images showed them so close that they appeared as a single object, indicating that a docking or refuelling operation may soon take place.

What Are These Satellites?

• Shijian-25: Launched in January 2024, this satellite was specifically designed to test on-orbit refuelling and satellite life-extension technologies. Its mission is to demonstrate how satellites already in orbit can be serviced and their lifespan extended, helping reduce costs and address the growing issue of space debris.

• Shijian-21: Launched in 2021, it made headlines in 2022 after using its onboard thrusters to move a defunct BeiDou navigation satellite out of operational orbit into a “graveyard orbit,” showcasing China’s capabilities in space debris management.

Both satellites were developed by the Shanghai Academy of Spaceflight Technology, part of the China Aerospace Science and Technology Corporation (CASC).

Why Is This a Big Deal?

Performing satellite refuelling in geostationary orbit is a highly complex task. The challenges include:

• Autonomous docking between two free-flying objects moving at about 11,000 km/h

• Precise control to avoid collision in the vastness of space

• Safe and effective fluid transfer in microgravity conditions

If successful, this would be a global first. While the US Defense Advanced Research Projects Agency (DARPA) carried out a similar test in low-Earth orbit in 2007 (called Orbital Express), it was far simpler. NASA’s ambitious OSAM-1 mission, which aimed for similar in-space servicing, was cancelled in 2023 after repeated delays and technical hurdles.

Global Space Race Tensions

The United States is closely watching these developments. American surveillance satellites, USA 270 and USA 271, have reportedly positioned themselves near the Chinese spacecraft since early June, according to US-based space situational awareness firm COMSPOC. This reflects not only the technical importance but also the strategic military implications of such technology.

The Shijian-21, originally described as a space debris mitigation tool, also has the potential to act as a space tug — a vehicle capable of moving or disabling other satellites, raising concerns about its possible anti-satellite (ASAT) use in future space conflicts.

What Happens Next?

Earlier in June, the two satellites approached within 1 km of each other but separated after 90 minutes — possibly a rehearsal for docking or an aborted attempt. Now, with orbits nearly synchronised and robotic arms on Shijian-25 ready, all signs suggest the actual refuelling test is imminent.

If completed successfully, it would mark a new chapter in space operations — allowing countries to repair, refuel, or upgrade satellites in orbit without launching replacements, saving millions of dollars and helping manage the growing congestion in Earth’s orbits.

China’s upcoming satellite refuelling test represents a bold leap in space technology and signals Beijing’s growing ambitions in both civilian and military space capabilities. As nations like the US, Russia, and China increasingly compete in this domain, such achievements could reshape how the world manages satellites, space debris, and orbital security in the years ahead.