| Primary satellite | Secondary satellite |
| Name | Cosmos 1821 Rocket | Kosmos-1553 |
| Spacetrack catalog number | 17526 | 14973 |
| Radar cross section | large | large |
| Epoch of two-line elements (UTC) | 2021 Jan 23 19:53 | 2021 Jan 23 18:20 |
| Time of closest approach (UTC) | 2020 Nov 29 17:33:17.543 |
| Minimum distance | 8.211 km |
| Height difference | -2.953 km |
| Relative speed | 13.604 km/s |
| Angle between velocity vectors | 136° |
| Geographic position | 71.0°S, 176.1°W |
| Height | 1007 km |
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