| Primary satellite | Secondary satellite |
| Name | Cosmos 858 Rocket | COSMOS 2251 DEB |
| Spacetrack catalog number | 9444 | 33842 |
| Radar cross section | large | small |
| Epoch of two-line elements (UTC) | 2021 Jan 20 04:37 | 2021 Jan 20 02:32 |
| Time of closest approach (UTC) | 2020 Nov 29 10:38:47.450 |
| Minimum distance | 30.527 km |
| Height difference | 5.157 km |
| Relative speed | 12.442 km/s |
| Angle between velocity vectors | 113° |
| Geographic position | 60.2°N, 61.9°W |
| Height | 776 km |
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