An infrared imaging sensor compatible with upgrade of second generation forward looking infrared (FLIR) B-kits, comprising: a set of refractive opto-mechanical modules configured to receive and create video from infrared electromagnetic radiation in at least the mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral bands, the set of refractive opto-mechanical modules including an afocal optical module having an eyepiece, wherein the eyepiece is a focus cell for the sensor, the afocal optical module being configured to receive and magnify the electromagnetic radiation in the MWIR and LWIR spectral bands and to output magnified electromagnetic radiation via the focus cell and configured to provide a plurality of different fields of view for the infrared imaging sensor, said afocal optical module comprising a plurality of field of view cells (320, 330, 340), each configured to provide one of the plurality of fields of view; a receiver assembly including a detector in a Dewar optically coupled to the focus cell and configured to receive the infrared electromagnetic radiation from the focus cell and to generate an electronic image from the infrared electromagnetic radiation; and at least one electronics module configured to provide an electronic interface for the infrared imaging sensor, and to process the electronic image; and characterized in that: the plurality of FOV cells (320, 330, 340) are disposed on a rotating structure that is configured to rotate with respect to the focus cell so as to align one of the plurality of FOV cells (320, 330, 340) with the focus cell; and further characterized by: a thermal reference source disposed on the rotating structure, wherein the thermal reference source is configured to be moved into an optical path of the focus cell and to provide a shutter mechanism for the sensor. a set of refractive opto-mechanical modules configured to receive and create video from infrared electromagnetic radiation in at least the mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral bands, the set of refractive opto-mechanical modules including an afocal optical module having an eyepiece, wherein the eyepiece is a focus cell for the sensor, the afocal optical module being configured to receive and magnify the electromagnetic radiation in the MWIR and LWIR spectral bands and to output magnified electromagnetic radiation via the focus cell and configured to provide a plurality of different fields of view for the infrared imaging sensor, said afocal optical module comprising a plurality of field of view cells (320, 330, 340), each configured to provide one of the plurality of fields of view; a receiver assembly including a detector in a Dewar optically coupled to the focus cell and configured to receive the infrared electromagnetic radiation from the focus cell and to generate an electronic image from the infrared electromagnetic radiation; and at least one electronics module configured to provide an electronic interface for the infrared imaging sensor, and to process the electronic image; and characterized in that: the plurality of FOV cells (320, 330, 340) are disposed on a rotating structure that is configured to rotate with respect to the focus cell so as to align one of the plurality of FOV cells (320, 330, 340) with the focus cell; and further characterized by: a thermal reference source disposed on the rotating structure, wherein the thermal reference source is configured to be moved into an optical path of the focus cell and to provide a shutter mechanism for the sensor.