The far-infrared spectroscopy of the troposphere (FIRST) project

The radiative balance of the Earth is influenced strongly by radiative cooling associated with emission of radiation by water vapor at far-infrared (far-IR) wavelengths greater than 15 mum and extending out beyond 60 mum. The distribution of water vapor and associated far-IR radiative forcings and feedbacks are well-recognized as major uncertainties in understanding and predicting future climate. Up to half of the outgoing longwave radiation (OLR) from the Earth occurs beyond 15.4 mum. Cirrus clouds also modulate the outgoing longwave radiation in the far-IR. Despite this fundamental importance, far-IR emission (spectra or band-integrated) has rarely been directly measured from space, airborne, or ground-based platforms. Current and planned operational and research satellites typically observe the mid-infrared only to about 15.4 mum. The Far-Infrared Spectroscopy of the Troposphere (FIRST) project is an investment by NASA through the Instrument Incubator Program (IIP) to develop a space-based capability to measure the spectrally resolved infrared spectrum to 100 mum.