Issue 123

Yaogan-35/36/39/42 Formation Update

22 Jun: China continues to evolve the formations of the 15 Yaogan triplets (45 satellites) it launched between 2021-2023. While none of the triplets remain in their original configuration of Lead-Trail1-Trail2, China continues to actively maintain the orbits of at least 35 of the 45 satellites. YG-36 05 & YG-39 01-05…

22 Jun: China continues to evolve the formations of the 15 Yaogan triplets (45 satellites) it launched between 2021-2023. While none of the triplets remain in their original configuration of Lead-Trail1-Trail2, China continues to actively maintain the orbits of at least 35 of the 45 satellites.

YG-36 05 & YG-39 01-05 (6 Triplets, 18 Satellites)

  • Lead/Trail1 Satellites: China is maintaining Lead and Trail1 formations for YG-36 05 and all 5 YG-39 triplets: 1) YG-36 05C/B; 2) YG-39 01C/B; 3) YG-39 02B/C; 4) YG-39 03C/B; 5) YG-39 04C/B; & 6) YG-39 05B/C). All 12 satellites are orbiting at ~515.9km with average altitude difference between the Lead and Trail1 satellites of only ~80m. As a result, the Lead-Trail1 satellites maintain their relative positions with one another. Lead is in front of the Trail1 satellite by 4-6 minutes. (see graphics next page)
  • Trail2 Satellites: The 6 Trail2 satellites are also maintaining their operational orbits near their historical average of 497km. However, they are orbiting ~19km lower than their Lead/Trail1 counterparts and are not maintaining their relative position with either of these satellites (10:1 rule). Operating at different altitudes also results in developing a RAAN offset with the Lead/Trail1 satellites. As of 22 Jun the average RAAN offset between the Trail2 satellites and Lead/Trail1 satellites is ~3.9°. This is greater than the RAAN offset China deliberately established with its older triplets (about 3.6°) and I’m beginning to wonder if China will ever bring the band back together. To do so, China will need to match the average altitudes of all 3 satellites in each triplet.

 

YG-35 01-05 & YG-36 01-04 (9 Triplets, 27 Satellites)

  • Lead Satellites: China has not maneuvered any of the Lead satellites in the past 3 months. The satellites are now operating at an average altitude of 468km well below their historical average of ~497km.
  • Trail1 Satellites: China continues to maintain the orbits of 8 of the 9 Trail1 satellites. All 8 are operating at an average altitude of 515.3km which above their historical average of ~497km and nearly identical to the current average altitudes of the YG-36 05 and YG-39 Lead/Trail1 satellites noted above. The one exception is YG-36 02B (54043) which last increased its average altitude in March 2025 but not to the same extent as any of the other Trail1 satellites. I suspect this satellite may have suffered an anomaly. (See Graph).
  • Trail2 Satellites: China continues to maintain the orbits of all 9 Trail2 satellites. 8 of the 9 are operating at their historical average altitude of 497km. The one exception is YG-35 03A (53316) which did not maneuver from 29 Jan – 11 Nov 2024 resulting in a loss of altitude from 496.3km to 431.3km (I thought it was a goner). However, China has been slowly increasing YG-35 03A’s average altitude for the past several months and it has climbed back to 465km.

 

Editor’s Comment: None of the 15 triplets are in their original formations. China continues to maintain 6 Lead/Trail1 formations. Only 6 of the 15 Lead satellites are maintaining their orbits. China is maintaining the orbits of 14 of the 15 Trail1 satellites at ~516km. China is maintaining the orbits of 14 of the 15 Trail2 satellites at ~497km.


Historical Context: Recall that for the first 2 years these satellites remained in predictable formation with one another, with one lead satellite about 5-7 minutes ahead of the first trail satellite (Trail1) which was itself about 1-3 minutes ahead of the second trail satellite (Trail2). In the 8 April Integrity Flash I noted that China appeared to be “pulling the plug” on the first 9 triplets (YG-35 01-05 & YG-36 01-04) by raising the average altitude of only the Trail1 satellites. Then in the 4 May edition, I noticed China raised the average altitudes of both the Lead and Trail1 satellites in the remaining 6 triplets without raising the average altitude of their Trail2 counterparts. As a result none of the 15 YG-35/36/39 triplets have maintained their original formations.