What is the required separation of an aircraft from the edge of airspace when radar separation is being used and the aircraft is less than 40 miles from the radar antenna?

The required separation of an aircraft from the edge of airspace when radar separation is being utilized, particularly when the aircraft is less than 40 miles from the radar antenna, is set to maintain safety and efficiency in air traffic control operations. In this case, the correct requirement is 1.5 miles.

This distance is specifically established to ensure that aircraft can be safely separated even when operating in close proximity to controlled airspace. The smaller separation distance as compared to other options reflects the reliance on radar technology that provides real-time tracking, enabling more precise navigation and separation strategies. This is particularly important near the boundaries of airspace, where traffic density can be higher, and the risk of encroachment on restricted or controlled areas must be minimized.

The other options suggest larger distances which are not necessary in this specific scenario and could result in less efficient use of airspace by unnecessarily widening the separation margin.