Calibration and performance assessment of the Far-Infrared Spectroscopy of the Troposphere sensor

NASA has developed the Far-Infrared Spectroscopy of the Troposphere (FIRST) sensor to provide spectrally resolved measurements of outgoing longwave atmospheric radiation over the wavelength range 10-100 µm, with high spatial and temporal resolution. The sensor was calibrated during the spring of 2005 and flown on a high-altitude balloon on June 7 of the same year. After a brief overview of the instrument design and data reduction procedure, we summarize the instrument performance measured during calibration and demonstrated during the balloon flight. Details of the measurement accuracy, precision, and instrument line shape are discussed, and spectra from FIRST are compared with model calculations and with measurements made during an overpass of the AQUA satellite.