A system including a sensor to receive scattered light from a scene in a thermal infrared spectral region, a Modified Integrated Thermal (MIT) band filter to acquire MIT band data within a thermal detection bandwidth, a sub-band filter to acquire a first sub-band data within a first sub-band bandwidth which is within the thermal detection bandwidth. The sub-band filter is a Reference band filter to capture Reference band data or a Reststrahlen band filter to capture Reststrahlen band data. The system also includes one or more processors configured to perform differencing of the MIT band data and the first sub-band data to compute a second sub-band data. The computed second sub-band data is Reference band data when the sub-band filter is the Reststrahlen band filter or the computed second sub-band data is Reststrahlen band data when the sub-band filter is the Reference band filter. A method and a computer software product are also disclosed.