Issue 107

Odd Couple Update: Yaogan-41 and TJS-11 Revisited

8 Oct: We took a look at the station keeping maneuver schedules for both Yaogan-41 (58582) and TJS-11 (59020) in the 21 July 2024 edition of the Flash. At that time the maneuvers appeared to be synchronized, potentially to maintain consistent orbit phasing for both spacecraft. Both satellites conducted 3 station…

8 Oct: We took a look at the station keeping maneuver schedules for both Yaogan-41 (58582) and TJS-11 (59020) in the 21 July 2024 edition of the Flash. At that time the maneuvers appeared to be synchronized, potentially to maintain consistent orbit phasing for both spacecraft. Both satellites conducted 3 station keeping maneuvers between 19 July and 8 Oct 2024. On average the most recent 3 maneuvers occurred within 6.3 days of one another. The previous 5 maneuvers occurred an average of 2.6 days of one another. The satellites remain close in their relative orbital positions with YG-41 crossing the equatorial plane ~1hr 7min ahead of TJS-11. In mid-July YG-41 crossed the equatorial plane ~1hr 6min ahead of TJS-11.

– China launched Yaogan-41 on 15 Dec 2023 and it is believed to be an imagery satellite capable of 5m resolution.

– China launched TJS-11 on 23 Feb 2024 and its mission is unknown. Other TJS missions have been associated with missile warning, signals intelligence, and satellite inspection.

– China used its largest rocket, the LM-5B, equipped with an extended fairing for both launches.

– TJS-11 is located between Gaofen-13-01 (46610) (2.4° separation) and YG-41 (3° separation). Gaofen-13-01 is also a GEO imagery satellite.

– At 5.1° inclination TJS-11’s orbit is the most inclined of any of the TJS satellite family. YG-41’s orbit is inclined 4.4° which is greater than China’s other electro-optical GEO based imagers.

-The inclination of both satellites has declined 0.4° in the past 5 months. Decline appears to be natural orbit evolution.

– TJS-11 arrived in GEO 70 days after YG-41, and the two orbits appeared to track closely with one another from the start, with TJS-11 slightly trailing YG-41 as they completed their “figure 8” orbital pattern.

– The station keeping timing has diverged over the past 3 months going from an average difference of 2.6 days for the first 5 maneuvers to an average of 6.3 days.

-In spite of the growing timing divergence the orbit phasing remains nearly unchanged. YG-41 “led” TJS-11 by ~1hr 6min on 16 July 2024. On 8 Oct 2024 YG-41 was ~1hr 7min ahead of TJS-11.

– Station keeping maneuvers for both satellites are similar in magnitude, with TJS-11 decreasing its SMA an average of 3.3km and YG-41 decreasing its SMA an average of 3.8km.