| Primary satellite | Secondary satellite |
| Name | Cosmos 858 Rocket | ERS 1 DEB |
| Spacetrack catalog number | 9444 | 35260 |
| Radar cross section | large | small |
| Epoch of two-line elements (UTC) | 2021 Jan 23 17:46 | 2021 Jan 23 21:57 |
| Time of closest approach (UTC) | 2020 Dec 01 19:04:48.514 |
| Minimum distance | 5.060 km |
| Height difference | 1.620 km |
| Relative speed | 14.910 km/s |
| Angle between velocity vectors | 173° |
| Geographic position | 8.2°S, 132.9°E |
| Height | 760 km |
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