LeoLabs Tracks Secretive Chinese SJ-15 Satellite Moments Before Fiery Reentry

Commercial Radar Captures Chinese Mystery Satellite’s Final Hours

In a significant demonstration of commercial space situational awareness (SSA) capabilities, the startup LeoLabs successfully tracked a highly secretive Chinese government payload, the Shijian-15 (SJ-15) satellite, just hours before its destructive, uncontrolled reentry into Earth’s atmosphere. The event, captured in LeoLabs’ radar data on January 19, 2025, provides a rare glimpse into the final moments of a long-duration, classified mission.

The SJ-15 had been a source of mystery for the space community, having operated for nearly five years in the crowded Geostationary Orbit (GEO) region, far above the typical Low Earth Orbit (LEO) where LeoLabs usually focuses its tracking efforts. Its sudden descent and subsequent tracking highlight the increasing ability of private companies to monitor sensitive, high-altitude government assets.

The Enigma of the SJ-15 Satellite

Launched in 2010, the SJ-15 was part of China’s Shijian (Practice) series, which often involves testing advanced or classified space technologies. The U.S. Space Force had been tracking the object, officially designating it as Object 36506.

While the exact purpose of the SJ-15 was never publicly disclosed by Beijing, it was described generally as a “test of new technologies.” For the last five years of its operational life, the satellite had resided in the graveyard orbit—a disposal zone located several hundred kilometers above the operational GEO belt (approximately 36,000 km above Earth). This maneuver is standard practice to prevent defunct satellites from colliding with active spacecraft.

Key Facts About the SJ-15 Mission:

• Launch Year: 2010
• Orbit Type: Geostationary Orbit (GEO) and subsequent Graveyard Orbit
• Duration in Graveyard Orbit: Approximately five years
• Designation: Object 36506 (U.S. Space Force)
• End State: Uncontrolled, destructive atmospheric reentry

Its long tenure in the graveyard orbit before its final descent makes the SJ-15’s end-of-life sequence particularly noteworthy, demonstrating a deliberate, though unannounced, decision to de-orbit the asset.

LeoLabs’ Unprecedented Tracking Feat

LeoLabs, a company specializing in tracking debris and active satellites primarily in LEO (below 2,000 km), managed to capture the descending SJ-15 using its global network of powerful radars. The tracking was achieved using the company’s Kiwi Space Radar located in New Zealand.

Tracking an object descending from GEO is challenging because these satellites are typically far outside the optimal range and sensitivity of LEO-focused radar systems. However, as the SJ-15 began its final plunge, its trajectory brought it into the effective range of LeoLabs’ sensors.

LeoLabs successfully captured the object in their radar data for approximately 12 hours before it finally reentered the atmosphere. This brief window allowed the commercial firm to provide crucial, real-time data on the final trajectory of the secretive spacecraft.

Why Commercial Tracking Matters

The successful capture of SJ-15 by a commercial entity like LeoLabs underscores a fundamental shift in space monitoring:

1. Enhanced Transparency: Commercial SSA provides independent verification of government space activities, enhancing global transparency and accountability.
2. Debris Mitigation: Real-time tracking of uncontrolled reentries, especially from high orbits, is vital for predicting impact zones and mitigating potential risks to ground populations and aviation.
3. Technological Advancement: It proves that ground-based commercial radar networks are becoming sophisticated enough to track objects across vast orbital regimes, bridging the gap between LEO and GEO monitoring.

Implications for Space Debris and Geopolitics

The uncontrolled reentry of a large, high-altitude satellite like the SJ-15 raises important questions regarding international norms for end-of-life disposal. While the satellite was initially placed in a graveyard orbit, the decision to allow its final reentry to be uncontrolled means that the timing and location of its atmospheric breakup were unpredictable.

Governments and commercial operators are increasingly pressured to adopt controlled de-orbiting procedures, especially for objects that pose a potential risk to the ground or to other spacecraft during their descent through LEO.

This event serves as a powerful reminder of the growing need for comprehensive, independent monitoring of all orbital regimes, particularly as major space powers continue to launch classified payloads and as the volume of space debris accelerates.

Key Takeaways

• The Event: The secretive Chinese SJ-15 satellite, launched in 2010, underwent an uncontrolled, destructive reentry into Earth’s atmosphere.
• The Tracker: Space situational awareness startup LeoLabs successfully tracked the satellite for 12 hours using its Kiwi Space Radar in New Zealand.
• Significance: This tracking demonstrates the growing capability of commercial SSA networks to monitor high-altitude, secretive government assets, even those descending from the Geostationary Orbit (GEO) belt.
• Context: SJ-15 had spent nearly five years in a designated graveyard orbit before its final descent, highlighting the challenges of end-of-life disposal for long-duration GEO missions.

Conclusion: The Future of Space Monitoring

The final tracking of the SJ-15 by LeoLabs is a milestone for the commercial space industry. It confirms that the monitoring of the orbital environment is no longer solely the domain of military or government agencies. As the space domain becomes more congested and contested, independent, precise, and timely data provided by companies like LeoLabs will be essential for maintaining orbital safety, enforcing transparency, and ensuring responsible space stewardship globally.