The student pilot was operating the last sector of a solo navigation exercise, tracking from Murray Bridge to Adelaide where a touch-and-go landing was made, before returning to Parafield at 1,500ft. Parafield Tower cleared the aircraft for a straight-in approach to runway 03 L, with a clearance to land. The pilot reported on final at 1,500ft, but the aircraft was not initially sighted by the controller. It was then observed north west of the field, inside the RAAF Edinburgh Control Zone. An Orion aircraft, conducting right hand circuits for runway 36 at Edinburgh, was on right base heading west when the other aircraft entered the control zone. Radar plots revealed that VH-YHH passed behind the Orion at about the same level, with a horizontal separation of about 1000 metres. The student pilot then made a right turn to enter left downwind for runway 03 L, Parafield, and continued for a landing.