According to an embodiment of the disclosure, an optical sensor system comprises a mast, a mast mirror, a navigation unit, one or more faceted mirrors, and at least two beam-steering mirrors. The mast is elevated from a vehicle. The mast mirror reflects signals either to or from object space along a line of sight. The navigation unit determines a location and attitude of the mast mirror. The one or more faceted mirrors reflect an error sensing beam to reveal a flexure of the mast mirror. The at least two beam-steering mirrors prevent the line of sight for the signals reflected off the mast mirror from walking off the mast mirror by adjusting an angle and translation of the signals reflected off the mast mirror.