| Primary satellite | Secondary satellite |
| Name | Cosmos 1821 Rocket | FENGYUN 1C DEB |
| Spacetrack catalog number | 17526 | 29965 |
| Radar cross section | large | small |
| Epoch of two-line elements (UTC) | 2021 Jan 15 14:48 | 2021 Jan 16 02:04 |
| Time of closest approach (UTC) | 2020 Nov 28 18:40:16.637 |
| Minimum distance | 4.488 km |
| Height difference | -1.283 km |
| Relative speed | 14.612 km/s |
| Angle between velocity vectors | 176° |
| Geographic position | 63.7°S, 24.4°E |
| Height | 1024 km |
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