Issue 117

Creeping Entropy: 4 of 15 Yaogan Triplets Struggle

21 Mar: I’ve been tracking the status of Yaogan-35/36/39/42 triplet formations for nearly 2 years . I’ve noticed a 5 of the 15 formations appear to be struggling (or at least not following their previous pattern). Here is a status update on the 5 outliers. Background: Between 6 Nov 2021 and 10 Dec 2023 China conducted…

21 Mar: I’ve been tracking the status of Yaogan-35/36/39/42 triplet formations for nearly 2 years. I’ve noticed a 5 of the 15 formations appear to be struggling (or at least not following their previous pattern). Here is a status update on the 5 outliers.


Background:

Between 6 Nov 2021 and 10 Dec 2023 China conducted 15 LM-2D launches and placed 45 Yaogan satellites into 5 orbital planes (500km SMA and 35° inclination but different RAAN/twist.) Each launch contained 3 satellites which deployed into a Lead, Trail1, Trail2 formation. Each plane had 9 of these satellites, 3 YG-35, 3 YG-36 and 3 YG-39. It appears 4 of the 5 YG-35 triplets are experiencing some difficulties.

Problem Kids: (Lead/Trail1/Trail2)

  • Yaogan-35 01 (49391/49390/49393): Launched 6 Nov 2021, this trio has completely fallen apart. The lead satellite has not increased its average altitude in over 11 months and is now orbiting under 400km and appears to be heading for re-entry. The Trail2 satellite has decreased its average altitude independent from the other two satellites several times since 2023 and as a result now has a significant RAAN offset from Trail1. For its part, the Trail1 satellite has maintained its average altitude since launch and recently increased it to 510km, which is the highest it has ever achieved.




  • Yaogan-35 02 (52908/52907/59395): Original 3 satellites launched 23 June 2022. After Trail2 satellite failed (has re-entered), China launched Yaogan-42 01 on 2 April 2024 (mislabeled in Spacetrack.org catalog as YG-42 02). More recently, the Lead satellite last increased its average altitude on 7 Feb 2025 and has lost 17km through 23 Mar 2025. As a result it has increased its lead from Trail1 and Trail2 satellites significantly.




  • Yaogan-36 02 (54045/54043/54042): Launched 14 Oct 2024. The lead satellite last increased its average altitude on 9 Dec 2024 and has lost 16km through 23 Mar 2025. As a result it has significantly increased its separation from Trail1 and Trail2 satellites. Trail1 and Trail2 satellites continue to maintain their average altitudes.




  • Yaogan-35 03 (53320/53318/53316): Launched 29 Jul 2022. Trail2 satellite did not maintain its average altitude from late Jan 2024 – Oct 2024 and as a result lost 63km in altitude and now has a RAAN difference of over 48°. I was surprised to see the Trail2 satellite begin to increase its average orbit in Nov 2024. The satellite continues to slowly increase its SMA but it will never return to formation. The Lead satellite last increased its average altitude on 21 Feb and has dropped 15km in altitude and is increasing its separation with Trail1 (from 451 sec to 1,648 sec).




  •  Yaogan-35 04 (53524/53526/53522): Launched 19 Aug 2022. This trio may be ok, but recently the Trail1 satellite increased its average altitude nearly 22km and rapidly fell behind the Lead and Trail2 satellites. Curious that the Trail1 satellite for YG-35 01 recently did something similar.