| Primary satellite | Secondary satellite |
| Name | Cosmos 1666 | COSMOS 2251 DEB |
| Spacetrack catalog number | 15889 | 36479 |
| Radar cross section | large | small |
| Epoch of two-line elements (UTC) | 2021 Jan 16 14:16 | 2021 Jan 15 18:19 |
| Time of closest approach (UTC) | 2020 Dec 08 12:26:21.957 |
| Minimum distance | 1566.869 km |
| Height difference | 8.075 km |
| Relative speed | 8.187 km/s |
| Angle between velocity vectors | 65° |
| Geographic position | 80.2°S, 138.6°E |
| Height | 529 km |
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