FIRST

Far-Infrared Spectroscopy of the Troposphere

SDL worked with the NASA Langley Research Center (LaRC) and the Smithsonian Astrophysical Observatory (SAO) to develop FIRST as part of NASA’s Instrument Incubator Program (IIP). FIRST has a noise equivalent temperature difference (NETD) goal of 0.2 K from 10 to 100 µm. The spectral resolution enables simultaneous retrievals of temperature and water vapor profiles.

SDL developed, integrated, and calibrated the instrument, and supported the balloon flight during the IIP portion of the program. The balloon was launched in June 2005 and the instrumentation successfully reported the vital and highly anticipated data. Subsequent high-altitude test campaigns in Chile and Colorado have also provided valuable data.

Why study this range? The radiative balance of the troposphere, and hence climate, is dominated by the infrared absorption and emission of water vapor, particularly at far–infrared (far–IR) wavelengths longer than 15 µm. Half of the Earth’s outgoing long–wave radiation occurs beyond 15.4 µm (650 cm–1). Determining the distribution of water vapor and its far–IR radiative forcings and feedbacks in this range could resolve uncertainties in understanding and predicting future climate and aid in understanding the greenhouse effect.