Posted on 07/15/2025 9:12:13 AM PDT by Red Badger
US-based COMSPOC and Swiss firm s2a systems tracked close proximity maneuvers between Shijian-21 and Shijian-25 from June to early July.
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China has reportedly performed a historic refueling mission in Earth’s orbit.
During the mission, two Chinese satellites appear to have docked in geostationary orbit, a report from the South China Morning Post reveals. One then refueled the other, marking an impressive milestone that no other nation has achieved.
While China’s space administration has not officially confirmed the operation was a success, a US space observation company observed the two satellites coming together.
Refueling technologies are a key evolution for orbital operations as well as human spaceflight. As crewed rockets use most of their fuel to reach orbit, these complex operations will be required to power these spacecraft out into deep space.
Shijan-21 and Shijan-25’s refueling operation
Between July 2 and July 6, China’s Shijian-21 and Shijian-25 satellites “appeared visually merged in optical sensor data”, US situational awareness software provider COMSPOC explained in a social media post.
“Given the prolonged RPO time, SJ-21 and SJ-25 may have docked,” it said, using the acronym for “rendezvous and proximity operations”.
Throughout June and July, COMSPOC observed the two satellites performing several close approaches in geosynchronous orbit. The first of these occurred on June 13, when Shijan-25 and Shijan-21 came with 1 km (0-6 miles) of each other after starting their close approach on June. They stayed in that position for roughly 90 minutes.
During the maneuver, two US surveillance satellites, USA 270 and USA 271, were positioned on either side of the Chinese satellites.
The two Chinese satellites performed another close-proximity operation on June 30, according to optical tracking images from Swiss space surveillance firm s2a systems. Both satellites were orbiting at an altitude of 35,786km (22,236 miles) above the equator at the time.
“After a day with small but relatively constant distance yesterday, the two objects came closer again today and can no longer be separated by our instrument since about 11:00 UTC (7pm Beijing time),” s2a systems said on July 2.
The importance of orbital refueling
Shijan-25 was launched in January this year, while Shijian-21 has been in space since 2021. The Shanghai Academy of Spaceflight Technology designed Shijan-25 satellites to test on-orbit refueling capabilities as well as operations that could extend a satellite’s life span.
In 2022, Shijan-21 was involved in a complex orbital operation. That year, the satellite docked with Beidou-2 G2, a defunct Chinese navigation satellite. Shijan-21 then towed the satellite to a “graveyard orbit” above GEO. The satellite used up most of its fuel in that operation. Now, it has reportedly been refueled by Shijan-25 in a historic world first.
The world’s leading space powers see in-orbit refueling is a key technology, crucial for future orbital operations as well as human space travel. The technology is a cornerstone of SpaceX and the US’ Starship program, which eventually aims to send humans to Mars. To fly humans to the Red Planet, a crewed Starship rocket will have to refuel in orbit to carry enough fuel for the long journey.
They’ve been refueling the International Space Station since 1999.
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