This paper describes the design and commissioning of an ultra-compact traverse system for the Engine Component Aerothermal (ECAT) facility at the University of Oxford, an engine-parts facility operating at engine-representative Mach and Reynolds numbers. The traverse system was required to be unusually compact to integrate within an existing upstream cassette system. The system has been used to perform detailed surveys of inlet total pressure, temperature, flow angles, velocity, and turbulence. The design and commissioning are described in detail. Example data is also provided. It is hoped that the novel design will be useful for other engineers involved in facility design.