Experimenting in GEO...A Look Back at LDPE-3A and SJ-23: Integrity Flash-Lite 9

Written by Greg Gillinger

LDPE-3A (55264), a US experimental satellite, had an interesting encounter with SJ-23 (55131), a Chinese test satellite, between Oct-Nov 2024.? Specifically,?LDPE-3A conducted?a series of maneuvers which resulted in a close approach (<25km) with SJ-23 with favorable lighting conditions for LDPE-3A to observe SJ-23. SJ-23 did not maneuver during this time period.??See Open Source?Video.?

Here is a timeline breakout + graphics of the interactions:

• Mid-September-28 October 2024: LDPE-3A was further east than SJ-23. On 28 October LDPE-3A was located over 111.2°E and SJ-23 was at 98.5°E (a difference of 12.7°)

• 29 Oct: LDPE-3A increased its SMA ~229km, reversing its 1.0° per day eastward drift and initiating a westward drift of ~1.9° per day.

• 30 Oct to 3 Nov: SJ-23 (which continued its 0.7° eastward drift) passed LDPE-3A moving east.

• 4 Nov: LDPE-3A decreased its altitude 192.2km and reversed its westward drift and initiated a 0.5° per day eastward drift.

• 4-5 Nov: LDPE-3A has two points of closest approach (POCA) with SJ-23.
• The first occured on 4 Nov at ~1945Z was <90km with optimal lighting conditions for LDPE-3A to observe SJ-23.

• The second POCA occurred 12 hours later at ~0745Z on 5 Nov. Range was <25km and again lighting conditions were favorable for LDPE-3A to observe SJ-23.

• 6-9 Nov: LDPE-3A falls further behind SJ-23 as SJ-23 is drifting 0.2° further east per day.
• 9 Nov: LDPE-3A reduces its SMA 15.4km and matches SJ-23's 0.7° per day eastward drift. With this change, LDPE-3A maintains its position ~ 0.7° behind SJ-23.

• 10 Nov-Present: SJ-23 remains 0.7° further east of LDPE-3A.?

?Putting all of the LDPE-3A maneuvers together looks like this on a Celestrak graph:

Cobra Maneuver?in GEO: LDPE-3A Oct through Nov 2024

Background:

• Per?Gunter’s Space Page: LDPE (Long Duration Propulsive EELV Secondary Payload Adapter (ESPA)) are experimental satellites built for the U.S. Air Force Space and Missiles Center (AFSMC) to carry small payloads and deploy small satellites.

• LDPE-3A was launched from Cape Canaveral, Florida on 15 Jan 2023 on a Falcon Heavy. It hosts five payloads, which remain attached...one of them, Catcher, is a prototype sensor designed to provide local space domain awareness insights. WASSAT...is a prototype wide-area sensor with four cameras that searches for and tracks other spacecraft and space debris in geosynchronous orbit. LDPE 3A also carries payloads from the military's Space Rapid Capabilities Office, two of which are operational prototypes for space situational awareness missions.?
• China launched Shijian-23 from Wenchang using a LM-7A on 9 Jan 2023. It was the first Shijian satellite to be launched on a LM-7A Space Launch Vehicle (SLV). Initially, analysts believed SJ-23 was a communications test satellite and a follow-on to theSJ-13. However, on 19 Jan 2023 SJ-23 released a small object. The release of a sub-payload is more indicative of SJ-17, TJS-3, and SJ-21. In its 2+ years on orbit SJ-23 has drifted between 19.8°E to 174.4°E and its most recent large maneuver was on 14 July 2024 when it decreased its SMA (altitude) to reverse its westward drift and begin drifting east at ~0.7° per day.

Meet the Author: Greg Gillinger: With 26 years in the U.S. Air Force and a career spanning strategic intelligence, space operations, and national security, Greg Gillinger brings unparalleled expertise to Integrity ISR. As Senior Vice President for Strategy & Development, Greg plays a pivotal role in advancing Space ISR capabilities and shaping the future of intelligence operations.

From leading ISR divisions at 14th Air Force and CSpOC to serving on the National Security Council, Greg’s experience reinforces Integrity ISR’s mission—delivering elite training, cutting-edge strategy, and operational excellence to defense forces worldwide.

We’re honored to have Greg’s leadership guiding our mission and proud to feature his insights through Integrity Flash.