An optical sensor assembly in which a four axis gimbal and dual coelostat mirror configuration provide pointing of the sensor line of sight in azimuth and elevation, stabilized for platform pitch. One example of a sensor system includes a first optical sub-system including a first plurality of optical elements, and a second optical sub-system configured to rotate about a first axis relative to the first optical sub-system. The second optical sub-system includes afocal foreoptics configured to direct a collimated beam of electromagnetic radiation to the first optical sub-system, a first coelostat minor configured to rotate about a second axis substantially perpendicular to the first axis, and a second coelostat mirror configured to rotate about a third axis substantially perpendicular to both the first axis and the second axis, and to receive electromagnetic radiation reflected by the first coelostat minor and to direct the electromagnetic radiation to the afocal foreoptics.