Two Chinese satellites have rendezvoused with one another more than 20,000 miles above the Earth in what analysts believe is the first high-altitude attempt at orbital refueling.
China’s Shijian-21 and Shijian-25 satellites, known as SJ-21 and SJ-25 for short, likely docked together in geosynchronous orbit sometime last week. This is the conclusion of multiple civilian satellite trackers using open source imagery showing the two satellites coming together, then becoming indistinguishable as a single object.
Chinese officials have released no recent public information on what the two satellites are up to, but they’ve said a bit about their missions in prior statements.
SJ-25, which launched in January, is designed “for the verification of satellite fuel replenishment and life extension service technologies,” according to the Shanghai Academy of Spaceflight Technology, the Chinese state-owned contractor that developed the satellite. SJ-21 launched in 2021 and docked with a defunct Chinese Beidou navigation satellite in geosynchronous orbit, then towed it to a higher altitude for disposal before returning to the geosynchronous belt. Chinese officials described this demonstration as a test of “space debris mitigation” techniques.
More Than Meets the Eye
These kinds of technologies are dual-use, meaning they have civilian and military applications. For example, a docking in geosynchronous orbit could foretell an emerging capability for China to approach, capture, and disable another country’s satellite. At the same time, the US Space Force is interested in orbital refueling as it seeks out ways to extend the lives of military satellites, which are often limited by finite fuel supplies.
The Space Force sometimes calls this concept dynamic space operations. While some military leaders remain skeptical about the payoff of in-space refueling, the Space Force has an agreement with Astroscale to perform the first refueling of a US military asset in orbit as soon as next year.
China appears to be poised to beat the US Space Force to the punch. The apparent docking of the two satellites last week suggests SJ-21 is the target for SJ-25’s refueling demonstration, and US officials are watching. Two of the Space Force’s inspector satellites, known by the acronym GSSAP, positioned themselves near SJ-21 and SJ-25 to get a closer look.
Retired Space Force lieutenant general John Shaw is a vocal proponent of dynamic space operations. Because of this, he’s interested in what happens with SJ-21 and SJ-25. Shaw was deputy commander of US Space Command before his retirement in 2023. In this role, Shaw had some oversight of GSSAP satellites as they roamed geosynchronous orbit.
“The theory behind dynamic space operations stemmed from a kind of operational frustration with our inability to conduct the full range of activities with GSSAP that we wanted to at Space Command, as the warfighter—largely due to the combination of fixed fuel availability and expected satellite lifetime,” Shaw told Ars.
As other countries, mainly China, step up their clandestine activities in orbit, military officials are asking more of the GSSAP satellites.
“It was operationally driven then, a couple years ago, but it’s now manifesting itself in much wider ways than even it did back then, particularly in the face of activities by potential adversaries,” Shaw said. “That’s why I’m more confident and even more fanatical about it.”