Precision in Motion: Advances in Robotic Polishing of X-Ray Mirrors

Recent efforts at NASA's Goddard Space Flight Centre aim to produce X-ray telescopes that deflect X-ray beams into an observatory's instruments at an extremely shallow angle, yielding high-resolution images. This necessitates exceptional surface slope precision on each individual aspheric mirror. Typical industrial robotic polishing accuracy remains well below the practical specifications of X-ray optics, due to undesired equipment vibrations that induce waviness in the polishing contact zone. It is therefore necessary to develop a method that can ensure consistent contact and accommodate for undesirable vibrational effects in the polishing equipment. This work presents a study on contact pressure fluctuations in the contact zone, validated by a statistical approach to counteract the imprinted vibration. A passive error compensator is introduced thereby maintaining uniform pressure, adhering to the planned material removal rate. Analysis of the experimental results verified the elimination of force overshoot, bringing us closer to the practical applicability of robot polishing to produce performance standard X-ray mirror segments.