A directed infrared countermeasures, DIRCM, system for use on an aircraft to track and jam a missile having a seeker, comprising: a dome; a two-axis gimbal configured to slew and point an optical axis; a receive telescope on the gimbal having a line-of-sight along said optical axis to receive incident radiation; a detector optically coupled to the receive telescope; a laser configured to emit a modulated laser beam in a transmit band; a transmit telescope on the gimbal along a transmit axis offset laterally from the optical axis but nominally aligned with the line-of-sight of the receive telescope, said telescope comprising an optical port offset from the transmit axis and optically coupled to the laser to receive and emit the laser beam and a reflective optical assembly comprising an off-axis mirror segment that reflects the emitted laser beam as a collimated beam towards the dome and an off-axis dome corrector lens segment that precompensates for dome aberrations induced in the beam by the lateral offset of the transmit telescope from the optical axis to transmit a collimated laser beam, wherein said off-axis dome corrector lens segment comprises a segment of a parent meniscus lens that corrects chromatic and standard aberrations over the dome, said lens segment corresponding to the lateral offset of the transmit telescope from the optical axis to the transmit axis, and wherein said off-axis mirror segment comprises a segment of a parent mirror having a parabolic base curvature about an axis of symmetry, said mirror segment corresponding to an offset from the axis of symmetry that lies on the transmit axis whereby the optical port does not obscure the reflected laser beam; and a processor that processes the incident radiation from the detector to slew the gimbal to track a missile and engages the laser to emit the modulated laser beam through the transmit telescope to jam the missile's seeker. a dome; a two-axis gimbal configured to slew and point an optical axis; a receive telescope on the gimbal having a line-of-sight along said optical axis to receive incident radiation; a detector optically coupled to the receive telescope; a laser configured to emit a modulated laser beam in a transmit band; a transmit telescope on the gimbal along a transmit axis offset laterally from the optical axis but nominally aligned with the line-of-sight of the receive telescope, said telescope comprising an optical port offset from the transmit axis and optically coupled to the laser to receive and emit the laser beam and a reflective optical assembly comprising an off-axis mirror segment that reflects the emitted laser beam as a collimated beam towards the dome and an off-axis dome corrector lens segment that precompensates for dome aberrations induced in the beam by the lateral offset of the transmit telescope from the optical axis to transmit a collimated laser beam, wherein said off-axis dome corrector lens segment comprises a segment of a parent meniscus lens that corrects chromatic and standard aberrations over the dome, said lens segment corresponding to the lateral offset of the transmit telescope from the optical axis to the transmit axis, and wherein said off-axis mirror segment comprises a segment of a parent mirror having a parabolic base curvature about an axis of symmetry, said mirror segment corresponding to an offset from the axis of symmetry that lies on the transmit axis whereby the optical port does not obscure the reflected laser beam; and a processor that processes the incident radiation from the detector to slew the gimbal to track a missile and engages the laser to emit the modulated laser beam through the transmit telescope to jam the missile's seeker.