The FireMapper is a high precision, airborne thermal imager developed through a Research Joint Venture between the USDA Forest Service, Pacific Southwest Research Station (PSW), and Space Instruments, Inc. FireMapper is intended as a quantitative instrument for mapping and monitoring the physical properties of wildland fires. Based on a microbolometer focal-plane array manufactured by BAE Systems, FireMapper incorporates two levels of on-board calibration, requires no cryogenic cooling, and images in a wide-band and two narrow-band channels in the thermal infrared spectrum. Fires are typically imaged with no saturation at a nominal wavelength of 12 micrometers and with little saturation at 9 micrometers. The broadband channel provides stable, radiometric measurements at typical earth-resource temperatures. As implemented aboard the PSW Airborne Sciences Aircraft, N127Z, the FireMapper radiometer is typically used in combination with a short-wave infrared InGaAs camera manufactured by Sensors Unlimited and two Kodak Megaplus 1.6 i cameras providing digital imaging at red and near-infrared wavelengths.