| Primary satellite | Secondary satellite |
| Name | Cosmos 1356 | FLOCK 2K 40 |
| Spacetrack catalog number | 13153 | 42865 |
| Radar cross section | large | small |
| Epoch of two-line elements (UTC) | 2021 Apr 13 03:26 | 2021 Apr 13 03:23 |
| Time of closest approach (UTC) | 2021 Mar 09 23:44:24.098 |
| Minimum distance | 835.602 km |
| Height difference | -4.961 km |
| Relative speed | 12.335 km/s |
| Angle between velocity vectors | 108° |
| Geographic position | 76.4°S, 169.6°W |
| Height | 471 km |
|