{
  "id": "shijian-21-25",
  "name": "Shijian-21 and Shijian-25",
  "aliases": [
    "SJ-21",
    "SJ-25"
  ],
  "domain": "space",
  "country": "CHN",
  "category": "On-orbit servicing and inspection satellites",
  "status": "in-service",
  "fielded": null,
  "operators": [
    "CHN"
  ],
  "summary": "Chinese GEO servicing satellites; SJ-21 towed a dead BeiDou satellite to a graveyard orbit and SJ-25 conducted probable refueling with SJ-21.",
  "specs": [
    {
      "k": "orbit_regime",
      "v": "GEO",
      "src": [
        "gsp-sj-21"
      ],
      "conf": "medium"
    },
    {
      "k": "first_launch",
      "v": 2021,
      "src": [
        "gsp-sj-21"
      ],
      "conf": "medium"
    },
    {
      "k": "mission",
      "v": "Rendezvous, docking, debris removal and refueling experiments",
      "src": [
        "gsp-sj-25"
      ],
      "conf": "medium"
    },
    {
      "k": "program",
      "v": "SJ-21 docked with BeiDou-2 G2 and moved it above GEO (January 2022); SJ-21 and SJ-25 maneuvered into extremely close proximity in probable refueling experiments",
      "src": [
        "ussf-space-threat-2025"
      ],
      "conf": "medium"
    },
    {
      "k": "on_orbit",
      "v": 2,
      "src": [
        "celestrak-gp"
      ],
      "conf": "high",
      "note": "Payloads with current element sets in the public catalog, active or not."
    },
    {
      "k": "active_sats",
      "v": 2,
      "src": [
        "celestrak-gp"
      ],
      "conf": "medium",
      "note": "Count in the CelesTrak active satellites list, which estimates operational status."
    },
    {
      "k": "perigee_km",
      "v": [
        35560,
        35599
      ],
      "src": [
        "celestrak-gp"
      ],
      "conf": "high",
      "note": "Active satellites per CelesTrak, element epoch about 2026-11-08."
    },
    {
      "k": "apogee_km",
      "v": [
        35974,
        36010
      ],
      "src": [
        "celestrak-gp"
      ],
      "conf": "high",
      "note": "Active satellites per CelesTrak, element epoch about 2026-11-08."
    },
    {
      "k": "period_min",
      "v": [
        1436,
        1436.1
      ],
      "src": [
        "celestrak-gp"
      ],
      "conf": "high",
      "note": "Active satellites per CelesTrak, element epoch about 2026-11-08."
    },
    {
      "k": "inclination_deg",
      "v": [
        5.39,
        5.45
      ],
      "src": [
        "celestrak-gp"
      ],
      "conf": "high",
      "note": "Active satellites per CelesTrak, element epoch about 2026-11-08."
    }
  ],
  "payloads": [],
  "variants": [],
  "art": "satellite",
  "image": null,
  "verified": null,
  "changelog": [
    {
      "date": "2026-11-08",
      "change": "Entry created from cited open sources"
    },
    {
      "date": "2026-11-08",
      "change": "Orbital elements from CelesTrak GP data (epoch about 2026-11-08): 2 catalogued, 2 active."
    }
  ],
  "satellites": [
    {
      "name": "SHIJIAN-21 (SJ-21)",
      "norad": 49330,
      "cospar": "2021-094A",
      "perigee_km": 35560,
      "apogee_km": 36010,
      "inclination_deg": 5.45,
      "period_min": 1436,
      "epoch": "2026-11-08",
      "active": true,
      "owner": "PRC",
      "launch": "2021-10-24"
    },
    {
      "name": "SHIJIAN-25 (SJ-25)",
      "norad": 62485,
      "cospar": "2025-002A",
      "perigee_km": 35599,
      "apogee_km": 35974,
      "inclination_deg": 5.39,
      "period_min": 1436.1,
      "epoch": "2026-10-15",
      "active": true,
      "owner": "PRC",
      "launch": "2025-01-06"
    }
  ],
  "url": "https://www.defensepedia.com/systems/shijian-21-25.html",
  "sources": {
    "gsp-sj-21": {
      "title": "Shi Jian 21 (SJ 21)",
      "publisher": "Gunter's Space Page",
      "url": "https://space.skyrocket.de/doc_sdat/sj-21.htm",
      "published": null,
      "tier": 3,
      "checked": "2026-11-08"
    },
    "gsp-sj-25": {
      "title": "Shi Jian 25 (SJ 25)",
      "publisher": "Gunter's Space Page",
      "url": "https://space.skyrocket.de/doc_sdat/sj-25.htm",
      "published": null,
      "tier": 3,
      "checked": "2026-11-08"
    },
    "ussf-space-threat-2025": {
      "title": "Space Threat Fact Sheet (current as of December 2025)",
      "publisher": "U.S. Space Force, Headquarters Space Force Intelligence",
      "url": "https://www.spaceforce.mil/About-Us/Fact-Sheets/Fact-Sheet-Display/Article/4297159/space-threat-fact-sheet",
      "published": "2025-12-01",
      "tier": 1,
      "checked": "2026-11-08"
    },
    "celestrak-gp": {
      "title": "NORAD GP element sets (current data)",
      "publisher": "CelesTrak (data from the U.S. Space Force 18th/19th Space Defense Squadron catalog)",
      "url": "https://celestrak.org/NORAD/elements/",
      "published": "2026-11-08",
      "tier": 1,
      "checked": "2026-11-08"
    }
  }
}