Pion-NKS 901 (Cosmos 2550) satellites are the maritime component of the new-generation ELINT satellite system Liana.
| Name of Satellite | Pion-NKS 901 (Cosmos 2550) |
| Purpose | Earth Observation |
| Contractor | KB Arsenal, RKTs Progress |
| Country of Contractor | Russia |
| Launch Mass (kg.) | 6 500 |
| Class of Orbit | LEO |
| Perigee (km) | 587 |
| Expected Lifetime (yrs.) | 5 |
| Date of Launch | 25.06.2021 |
| Launch Site | Plesetsk Cosmodrome |
| Launch Vehicle | Soyuz 2.1b |
| COSPAR Number | 2021-056A |
| NORAD Number | 48865 |
In Pion-NKS 901 Earth Observation Satellite both ELINT US-PM passive radar and US-A active radar were equipped with ELINT sensors and active radar as a replacement.
