Space & Technology — 2026-07-27

China Shijian-31 Satellite Sweeps Entire Geosynchronous Belt Using Novel Orbit for Space Surveillance

BLUFSJ-31 gives Beijing a low-cost, hard-to-characterize catalog of the entire geostationary belt, eroding the assumption that Western GEO assets operate beyond routine adversary surveillance.

China launched Shijian-31 (SJ-31) aboard a Long March 3B/E from Xichang on June 16 1. Initial TLE data analyzed by Integrity ISR placed the satellite in a highly elliptical, Molniya-type orbit inclined about 63.4 degrees, with an eccentricity of 0.69 and a 12.5-hour period 1. Unlike China's four other Molniya-class satellites, aligned for northern-latitude missile warning, SJ-31's perigee argument of about 171 degrees places apogee over the equator, extending dwell over the geostationary belt instead of the Arctic 1. Because its period runs slightly longer than a standard 12-hour Molniya orbit, each equatorial crossing shifts about 15.7 degrees in longitude, letting SJ-31 sweep the full GEO belt roughly every 23 days, per Integrity ISR, SpaceNews, KeepTrack, and Zamin.uz citing ComSpOC 1234. China's Aerospace Science and Technology Corporation (CASC) has said only that SJ-31 supports "space environment detection," without releasing satellite imagery 4.

Analysis
SJ-31's 171-degree argument of perigee, a deliberate departure from the 270-degree orientation of China's four missile-warning HEO satellites, marks it as a dedicated GEO surveillance design rather than a fifth early-warning asset, though the "space environment detection" label China assigns could describe genuine research consistent with earlier Shiyan and TJS-series work on refueling and space-situational studies. Passing 2,000 to 2,500 kilometers above GEO residents, an altitude poorly covered by LEO imagers or GEO inspectors like GSSAP, the satellite gives China persistent, hard-to-characterize custody of the belt without close-proximity operations, complicating US space domain awareness and adding conjunction-screening workload for USSPACECOM as it cycles through the belt roughly every 23 days. Two independently reported technical assessments trace back to a single underlying ComSpOC tracking dataset rather than fully independent verification.

4 sources