A hyper-thermal orbital aerodynamics test facility is described. The Rarefied Orbital Aerodynamics Research facility (ROAR) is a dedicated apparatus designed to simulate the atmospheric flow in very low Earth orbits (VLEO) to investigate the impact different material properties have on gas-surface interactions, and determine the aerodynamic properties of materials from the reemitted gas distribution. The main characteristics observed in VLEO to be reproduced are the free molecular flow regime and the flux of oxygen atoms at orbital velocities impinging on the spacecraft surface. This is accomplished by combining an ultra-high vacuum system with a hyper-thermal oxygen atoms generator. Materials performance will be assessed via a scattering experiment in which an atomic oxygen beam is incident on the surface of a test sample and the scattered species are recorded by mass spectrometers. The design of the experiment is discussed, from the specification of the vacuum components to the generation of oxygen atoms and their detection.