| Primary satellite | Secondary satellite |
| Name | Vanguard 1 | COSMOS 2251 DEB |
| Spacetrack catalog number | 5 | 34013 |
| Radar cross section | medium | small |
| Epoch of two-line elements (UTC) | 2021 Jan 16 09:33 | 2021 Jan 15 18:18 |
| Time of closest approach (UTC) | 2020 Dec 10 11:57:38.889 |
| Minimum distance | 445.824 km |
| Height difference | 2.757 km |
| Relative speed | 7.040 km/s |
| Angle between velocity vectors | 53° |
| Geographic position | 29.8°N, 156.4°W |
| Height | 650 km |
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