Soyuz 2.1b | Pion-NKS No. 1 (Kosmos 2550)

The Russian Pion-NKS (14F139) satellites are the naval component of the next generation ELINT satellite system Liana.

As a replacement for both the passive ELINT US-PM and the active radar US-A, they carry both ELINT sensors as well as an active radar.