An optical sensor system comprising: afocal foreoptics configured to receive and collimate electromagnetic radiation to provide a collimated beam of electromagnetic radiation, the afocal foreoptics including an all-reflective, reimaging mirror anastigmat; an imaging detector (184, 186); focal imaging optics positioned between the afocal foreoptics and the imaging detector and configured to receive the collimated beam of electromagnetic radiation from the afocal foreoptics and to focus the beam of electromagnetic radiation onto the imaging detector, the focal imaging optics including a reimaging -mirror anastigmat, the afocal foreoptics being configured to rotate about a first axis relative to the focal imaging optics and the imaging detector; and a scanning coelostat mirror configured to direct the electromagnetic radiation to the afocal foreoptics and to sweep a field of view of the imaging detector over a field of regard larger than the field of view, the afocal foreoptics being positioned between the scanning coelostat mirror and the focal imaging optics, and the field of view being determined at least in part by a combination of the afocal foreoptics and the focal imaging optics; and characterized in that the afocal foreoptics including an all-reflective, reimaging mirror anastigmat is an all-reflective, reimaging four-mirror anastigmat and in that the focal imaging optics including a reimaging mirror anastigmat is a focal imaging optics including a reimaging five-mirror anastigmat, and further wherein the field of view covers at least 5 degrees in elevation; and in that the four-mirror anastigmat of the afocal foreoptics includes: a primary mirror configured to receive and reflect the electromagnetic radiation from the coelostat mirror; a secondary mirror configured to receive and reflect the electromagnetic radiation from the primary mirror; a tertiary mirror configured to receive and reflect the electromagnetic radiation from the secondary mirror, the primary, secondary, and tertiary mirrors together constituting an objective that forms an intermediate image; and a quaternary mirror configured to refocus the intermediate image to infinity to produce the collimated beam of electromagnetic radiation, and to reflect the collimated beam of electromagnetic radiation toward the focal imaging optics. afocal foreoptics configured to receive and collimate electromagnetic radiation to provide a collimated beam of electromagnetic radiation, the afocal foreoptics including an all-reflective, reimaging mirror anastigmat; an imaging detector (184, 186); focal imaging optics positioned between the afocal foreoptics and the imaging detector and configured to receive the collimated beam of electromagnetic radiation from the afocal foreoptics and to focus the beam of electromagnetic radiation onto the imaging detector, the focal imaging optics including a reimaging -mirror anastigmat, the afocal foreoptics being configured to rotate about a first axis relative to the focal imaging optics and the imaging detector; and a scanning coelostat mirror configured to direct the electromagnetic radiation to the afocal foreoptics and to sweep a field of view of the imaging detector over a field of regard larger than the field of view, the afocal foreoptics being positioned between the scanning coelostat mirror and the focal imaging optics, and the field of view being determined at least in part by a combination of the afocal foreoptics and the focal imaging optics; and characterized in that the afocal foreoptics including an all-reflective, reimaging mirror anastigmat is an all-reflective, reimaging four-mirror anastigmat and in that the focal imaging optics including a reimaging mirror anastigmat is a focal imaging optics including a reimaging five-mirror anastigmat, and further wherein the field of view covers at least 5 degrees in elevation; and in that the four-mirror anastigmat of the afocal foreoptics includes: a primary mirror configured to receive and reflect the electromagnetic radiation from the coelostat mirror; a secondary mirror configured to receive and reflect the electromagnetic radiation from the primary mirror; a tertiary mirror configured to receive and reflect the electromagnetic radiation from the secondary mirror, the primary, secondary, and tertiary mirrors together constituting an objective that forms an intermediate image; and a quaternary mirror configured to refocus the intermediate image to infinity to produce the collimated beam of electromagnetic radiation, and to reflect the collimated beam of electromagnetic radiation toward the focal imaging optics. a primary mirror configured to receive and reflect the electromagnetic radiation from the coelostat mirror; a secondary mirror configured to receive and reflect the electromagnetic radiation from the primary mirror; a tertiary mirror configured to receive and reflect the electromagnetic radiation from the secondary mirror, the primary, secondary, and tertiary mirrors together constituting an objective that forms an intermediate image; and a quaternary mirror configured to refocus the intermediate image to infinity to produce the collimated beam of electromagnetic radiation, and to reflect the collimated beam of electromagnetic radiation toward the focal imaging optics.