The biggest upgrade Monopulse Secondary Surveillance Radar (MSSR) have over older beacon radars is they

• A. Can determine azimuth from one return of a transponder
• B. Do not require any radar returns
• C. Are cheaper to operate
• D. Provide weather data directly

Answer: (A)

Monopulse processing lets an SSR determine azimuth from a single transponder reply. Instead of needing multiple scans or sequential returns to infer angle, the antenna system forms several simultaneous beams and compares the signals (sum and difference patterns) to pinpoint the angle of arrival in one blink. This gives fast, accurate bearing information from one transponder return, which is the major upgrade MSSR provides over older beacon systems.

The transponder reply still provides range information from the round-trip time and carries identity (Mode A) and altitude (Mode C) data, but the key advancement is getting precise azimuth from that single return. The other choices aren’t accurate: it still relies on a radar return, it isn’t primarily about lowering operating costs, and it doesn’t inherently provide weather data.