What additional data does secondary surveillance radar (SSR) provide beyond primary radar?

What additional data does secondary surveillance radar (SSR) provide beyond primary radar?

• A. Weather information
• B. Ground speed only
• C. Identity and altitude via transponder replies, and with Mode S additional data
• D. Pilot remarks

Answer: (C)

Secondary surveillance radar provides data that the aircraft’s transponder replies with when interrogated. Primary radar only detects the object’s presence by bouncing radio waves off it, giving range and bearing but no identification or altitude. The transponder responds with an identity code (and, in the common altitude reporting mode, the aircraft’s altitude). When Mode S is used, the system can also transmit additional data beyond the basic identity and altitude, such as flight identification and other parameters. Weather information, ground speed, and pilot remarks aren’t conveyed by SSR, so the best description of what SSR adds is identity and altitude from transponder replies, with extra data available under Mode S.

Secondary surveillance radar provides data that the aircraft’s transponder replies with when interrogated. Primary radar only detects the object’s presence by bouncing radio waves off it, giving range and bearing but no identification or altitude. The transponder responds with an identity code (and, in the common altitude reporting mode, the aircraft’s altitude). When Mode S is used, the system can also transmit additional data beyond the basic identity and altitude, such as flight identification and other parameters. Weather information, ground speed, and pilot remarks aren’t conveyed by SSR, so the best description of what SSR adds is identity and altitude from transponder replies, with extra data available under Mode S.