Issue 119

20 Apr: On 16 August 2024 China launched a LM-4B with 9 “Yaogan-41” satellites on-board. The satellites went to a very familiar orbit, 35° inclined and 500km average altitude. Here’s the initial Flash article for context. After about a month China had maneuvered the satellites into a specific formation and were keeping the satellites at nearly the same average altitudes (within 500m) to maintain their relative positions with one another. A few weeks ago, I noticed this changed. Here’s what’s going on… Chinese space operators have not maintained the SMA of 5 of the 9 Yaogan-43 01 (60458-66) satellites resulting in changing positions between the satellites and an extension of the entire 9 satellite train. Yaogan-43 01A (60458), 01B (60459), 01D (60461), 01G (60464) and 01J (60466) are now orbiting at average altitudes below 495km and ~2km lower than their other YG-43 01 satellites. From ~11 Sep 2024 through 16 Mar 2025 the 9 YG-43 01 satellites were consistently in the same order: 1) Lead: 01E; 2) Trail1: 01D; 3) Trail2: 01G; 4) Trail3: 01J; 5) Trail4: 01B; 6) Trail5: 01A; 7) Trail6: 01F; 8) Trail7: 01H; and 9) Trail8: 01C. The average time separation between the Lead (01E) and Trail8 (01C) during this time was 31min 09sec. To maintain their relative distances all 9 satellites maintained an average altitude within ~355m of one another. From the available tracking data it appears China spent the first month (16 Aug – mid-Sep) deploying/maneuvering the satellites into the desired order and then spent the next 6 months orbiting within tight parameters, with each of the satellites maintaining its relative position to the satellite ahead and behind. The average altitude for all 9 satellites on 16 Mar 2025 was 496.6km. The constellation began to change in mid-March as the average altitudes of YG-43 01B, 01D and 01J slid below 496km. In late-Mar/early-Apr YG-43 01A and 01G also had their average altitudes drop below the historical average. Looking at the graphs below it does not appear as if China is actively lowering the satellites, rather China appears to have stopped conducting the necessary station-keeping and the orbits are naturally decaying. The average altitudes continue to decline for all 5 (see graphs). The order of the YG-43 01 satellites has changed significantly in the past 3 weeks with the satellites flying at lower altitudes steadily moving toward the front of the formation. As of 20 Apr 2025 the satellites are now in the following order (mover satellites in RED): 1) Lead: 01D; 2) Trail1: 01B; 3) Trail2: 01J; 4) Trail3: 01G; 5) Trail4: 01E; 6) Trail5: 01A; 7) Trail6: 01F; 8) Trail7: 01H; and 9) Trail8: 01C. The average altitude for the 5 “mover” satellites on 20 Apr 2025 was ~493.36km; the average for the other 4 satellites was 497.05km. The time difference between the Lead and Trail8 is now over 49 minutes, up from just over 31 minutes (a 58% increase). Without additional maneuvers, satellites D/B/J/G/A will eventually lap the other satellites. I can think of a few reasons why China may be re-arranging the YG-43 01 constellation:

• China concluded testing the original order after 6 months and are now re-arranging for further testing.
• China is creating RAAN differential between the 5 mover satellites and their counterparts and operating at different average altitudes is a fuel-efficient way to achieve this (we saw this with 7 “Trail2” YG-35/36 satellites in 2024).
• China is experiencing some anomaly on the 5 mover satellites and is currently unable to maintain their average altitudes. Kepler does the rest.

None of the changes are irreversible, but if the satellites use inter-satellite links these may be affected by the increased distances. Assuming the satellites can maneuver, China can reconstitute the constellation over a period of weeks (days if they maneuver aggressively). I looked at the YG-43 02/03 (60945-50 & 61617-19) constellation and do not see a similar pattern. All 9 satellites continue to maintain their average altitudes within 0.5km of one another and the time separation between Lead and Trail8 remains within historical averages. Of course these satellites launched later than YG-43 01, with 6x YG-43 02 satellites launching on 3 Sep 2024 and 3x YG-43 03 satellites launching on 23 Oct 2024. The 9 satellites organized into their current order on ~8 Jan 2025. I’ll keep checking in to see if a similar situation develops at the 6 month point (so early Jun 2025).

Then & Now: Comparing YG-43 01 Constellation 14 Mar 25 vs 19 Apr 25 (spacemap42.com)