THE SPECTRAL REGION BETWEEN 15 UM AND 100 UM IS REFERRED TO AS THE FAR-INFRARED (FAR-IR) PORTION OF THE SPECTRUM. THE FAR-IR RADIATION IS AN IMPORTANT COMPONENT OF THE RADIATION BUDGET OF THE EARTH-ATMOSPHERE SYSTEM. HOWEVER, THE SPECTRAL CHARACTERISTICS AND INFORMATION CONTENT OF THE FAR-IR RADIATION HAVE NOT BEEN EXTENSIVELY STUDIED IN COMPARISON WITH THEIR COUNTERPARTS FOR SHORTER SPECTRA. THE NOVEL FAR-INFRARED SPECTROSCOPY OF THE TROPOSPHERE (FIRST) INSTRUMENT DEVELOPED BY NASA (MLYNCZAK ET AL. 2006), WHICH IS A MICHELSON INTERFEROMETER, PROVIDES UNPRECEDENTED DATA SETS TO UNDERSTAND THE FAR-IR RADIATION. WE PROPOSE RESEARCH IN SUPPORT OF THE FIRST PROJECT. THE MAJOR OBJECTIVES OF TILE PROPOSED RESEARCH ARE AS FOLLOWS: - COMPARISON BETWEEN THE FIRST MEASUREMENTS AND SIMULATIONS BASED ON STATE-OF- THE-ART MODELING CAPABILITIES, AIMED AT THE VALIDATION OF THE FIRST INSTRUMENT FROM THEORETICAL PERSPECTIVE. - ANALYSES OF THE FIRST MEASUREMENTS TO UNDERSTAND THE SENSITIVITY OF THE FAR-IR RADIATION TO ATMOSPHERIC PROFILE (E.G., THE VERTICAL DISTRIBUTION OF TEMPERATURE AND PRESSURE) AND ATMOSPHERIC CONSTITUENTS (E.G., WATER VAPOR) WHICH ARE AVAILABLE FROM COLLOCATED DATA SETS OR RETRIEVAL PRODUCTS BASED ON OTHER INSTRUMENTS (E.G., THE ATMOSPHERIC INFRARED SOUNDER). - EXPLORATION OF THE INFORMATION CONTENT ABOUT ICE CLOUDS AND AEROSOLS IN THE FAR-IR RADIATION ON THE BASIS OF STATE-OF-THE-ART MODELING CAPABILITIES AND THE FIRST MEASUREMENTS, AIMED AT DEVELOPING OF ALGORITHMS TO RETRIEVING ICE CLOUD AND AEROSOL PROPERTIES FROM THE FAR-IR RADIATION.