Issue 127

China: Docked SJ-21/SJ-25 Conduct Plane Change Maneuver

16 Aug: China conducted significant plane change maneuvers with the docked SJ-21/25 (49330 & 62485) satellites. The 2 spacecraft have presumably been docked since 2 July 2025 when they became indistinguishable from terrestrial based space domain awareness sensors (optical, radar and signal based). The pair made minor…

16 Aug: China conducted significant plane change maneuvers with the docked SJ-21/25 (49330 & 62485) satellites. The 2 spacecraft have presumably been docked since 2 July 2025 when they became indistinguishable from terrestrial based space domain awareness sensors (optical, radar and signal based). The pair made minor maneuvers from 2-7 Aug, then from 8 – 15 August, Chinese space operators conducted several plane-changing maneuvers which resulted in a 6° reduction of the spacecraft’s inclination and a significant change in RAAN as well. Such maneuvers are highly fuel/energy intensive (see next article) and very rare.

– Maneuver Timeline (based on TLE values for SJ-21 as they appear more current than that of SJ-25…I suspect having two objects docked is proving problematic for cataloging):

  • 8 Aug (starting condition): Inclination = 10.4° SMA = 35,794.4km
  • 9 Aug (test maneuvers?): Inclination = 9.8° (-0.6) SMA = 35,790.8 (-3.8km)
  • 11-12 Aug (big move): Inclination = 4.4° (-5.4°) SMA = 35,759 (-32km)
  • 14-15 Aug (clean up): Inclination = 4.4° (no change) SMA = 35,783 (+24km)
  • 16 Aug: No changes, SJ-21/25 are cataloged with identical orbital information. Satellites are at 4.4° inclination and orbiting just 3km below the GEO belt. They are over 127° E longitude and drifting eastward at a negligible 0.03°/day.

 

Editor’s Comment: Where to start…to be clear China has not released any information regarding its refueling demonstration. They may have successfully completed refueling SJ-21 and then used SJ-25 to insert it into a new orbit with presumably a full load of propellant. I will be looking for the two satellites to either maneuver again or undock and go their separate ways. Unknown if China intends to use SJ-21 to conduct further “orbital debris mitigation” experiments. If so, it would make sense to release SJ-21 in a near plane-match with the intended target. China also has options with SJ-25. In its current orbit it is near the same inclination as TJS-11 (4.6°), TJS-19 (3.9°), YG-41 (3.7°) and SJ-23 (2.9°). Unknown if any of those spacecraft are refueling capable. China could also maneuver SJ-25 independently to a new refueling target. Watch this Space as events unfold!