The Russian (former USSR) BRLS-8B "Zaslon" (Barrier) is an all-weather multimode airborne radar developed between 1975 and 1980 by the Tikhomirov Scientific Research Institute of Instrument Design as part of the weapons control system of the MiG-31 supersonic interceptor.

The Zaslon is a pulse-Doppler radar with a passive electronically scanned array (PESA) antenna and digital signal processing.

This made it much harder for United States Air Force aircraft and cruise missiles to penetrate the Soviet airspace at low altitude (through terrain masking/clutter), without being detected.

[8] The basic differences between other versions and the MiG-31BM:[13] The onboard radar complex of the MiG-31BM can track 24 airborne targets at one time, 6 of which can be simultaneously attacked by R-33S missiles.

[8] The MiG-31 is one of only a few aircraft able to intercept and destroy cruise missiles flying at extremely low heights.