How many degrees of coverage does the RSDS provide around the aircraft?

The RSDS, or Radar System Development Service, is designed to provide a full circle of surveillance around the aircraft, which amounts to 360 degrees of coverage. This means that it can observe and track objects from all directions, thereby ensuring comprehensive situational awareness for any potential threats or navigational challenges. This full 360-degree coverage is essential for the safety and effectiveness of operations, allowing for timely responses to any events in the aircraft's vicinity.

The other choices suggest limited coverage areas such as 180, 270, or 90 degrees, which would restrict the system’s capability to monitor only parts of the environment around the aircraft. In contrast, 360 degrees enables optimum performance and safety, making it the correct answer in this context.