| Primary satellite | Secondary satellite |
| Name | Vanguard 1 | deb Kosmos-2125 |
| Spacetrack catalog number | 5 | 21918 |
| Radar cross section | medium | small |
| Epoch of two-line elements (UTC) | 2021 Jan 16 09:33 | 2021 Jan 15 13:04 |
| Time of closest approach (UTC) | 2020 Dec 02 22:14:54.195 |
| Minimum distance | 36.146 km |
| Height difference | 5.991 km |
| Relative speed | 11.170 km/s |
| Angle between velocity vectors | 100° |
| Geographic position | 21.7°S, 12.3°W |
| Height | 1487 km |
|