An optical sensor system comprising: a mast of variable height elevated from a ground vehicle ; a mast mirror configured to reflect signals to or from object space along a line of sight , the mast mirror positioned on top of the mast; a navigation unit configured to determine a location and attitude of the mast mirror; one or more error sensing modules , one of the one or more error sensing modules being configured to emit an error sensing beam ; one or more faceted mirrors , each of the one or more faceted mirrors having a plurality of facets, wherein the mast mirror is configured to direct the error sensing beam onto the one or more faceted mirrors, the one or more faceted mirrors configured to reflect the error sensing beam to travel back to one of the one or more error sensing modules via the mast mirror to be detected by the one of the one or more error sensing modules, the reflected error sensing beam revealing a flexure of the mast; one or more sensors configured to analyze the signals from object space, the one or more sensors positioned inside the vehicle; and at least two beam-steering mirrors configured to prevent the line of sight for the one or more sensors from walking off the mast mirror by adjusting an angle and translation of the signals reflected off the mast mirror, the adjustment of the at least two beam-steering mirrors based on the reflected error sensing beam detected by the one of the one or more error sensing modules; wherein the optical sensor system is configured such that angular movement of the mast mirror due to the flexure of the mast causes the error sensing beam to translate from one of the facets of the one or more faceted mirrors to another of the facets of the one or more faceted mirrors. a mast of variable height elevated from a ground vehicle ; a mast mirror configured to reflect signals to or from object space along a line of sight , the mast mirror positioned on top of the mast; a navigation unit configured to determine a location and attitude of the mast mirror; one or more error sensing modules , one of the one or more error sensing modules being configured to emit an error sensing beam ; one or more faceted mirrors , each of the one or more faceted mirrors having a plurality of facets, wherein the mast mirror is configured to direct the error sensing beam onto the one or more faceted mirrors, the one or more faceted mirrors configured to reflect the error sensing beam to travel back to one of the one or more error sensing modules via the mast mirror to be detected by the one of the one or more error sensing modules, the reflected error sensing beam revealing a flexure of the mast; one or more sensors configured to analyze the signals from object space, the one or more sensors positioned inside the vehicle; and at least two beam-steering mirrors configured to prevent the line of sight for the one or more sensors from walking off the mast mirror by adjusting an angle and translation of the signals reflected off the mast mirror, the adjustment of the at least two beam-steering mirrors based on the reflected error sensing beam detected by the one of the one or more error sensing modules; wherein the optical sensor system is configured such that angular movement of the mast mirror due to the flexure of the mast causes the error sensing beam to translate from one of the facets of the one or more faceted mirrors to another of the facets of the one or more faceted mirrors. <EOS>