Standoff detection, identification and quantification of chemicals require sensitive spectrometers with calibration capabilities. Recent developments in LWIR focal plane arrays combined with the mastering of Fourier-Transform Spectrometer technology allow the realization of an imaging spectrometer specifically designed for chemical imaging. The spectral and radiometric calibration of the instrument enables the processing of the data to detect the chemicals with spectral signatures in the 8-12 mum region. Spectral images are processed and the contrast between different pixels is used to map the chemicals. Telops is building the field-portable instrument. This paper presents the requirements for chemical detection in the LWIR how the system is broken down into different modules and the details of each of these modules: calibration. interferometer. datacube acquisition and processing, and the main controller. The system has real-time processing capabilities of the measured data. Performance prediction is presented as well.