THE CLOUD-AEROSOL LIDAR WITH ORTHOGONAL POLARIZATION (CALIPSO) IMAGING INFRARED RADIOMETER (IIR) MEASUREMENTS PROVIDE A UNIQUE OPPORTUNITY TO RETRIEVE ICE CLOUD PROPERTIES. TO BE MORE SPECIFIC, INFRARED CHANNELS ARE INDEPENDENT OF SOLAR RADIATION AND THUS CAN BE APPLIED TO BOTH DAYTIME AND NIGHTTIME CLOUD PROPERTY RETRIEVAL. FURTHERMORE, INFRARED CHANNELS ARE SENSITIVE TO OPTICALLY THIN CIRRUS CLOUDS AND INSENSITIVE TO THE OVERALL SHAPE AND SURFACE TEXTURE OF ICE CRYSTALS ASSUMED IN THE FORWARD LIGHT SCATTERING CALCULATION INVOLVED IN THE RETRIEVAL. ICE CLOUD PROPERTY RETRIEVAL BASED ON THE IIR OBSERVATIONS WILL BE COMPLIMENTARY TO THE EXISTING RETRIEVAL PRODUCTS BASED ON VISIBLE/NEAR-INFRARED DAYTIME ICE CLOUD PROPERTY PRODUCTS DERIVED FROM THE MODERATE RESOLUTION IMAGING SPECTROMETER (MODIS) OBSERVATIONS AND CALIPSO CALIOP LIDAR MEASUREMENTS. THE OVERARCHING GOAL OF THE PROPOSED RESEARCH IS TO DEVELOP COMPUTATIONALLY EFFICIENT ALGORITHMS TO RETRIEVE ICE CLOUD PROPERTIES (SPECIFICALLY, ICE CLOUD OPTICAL THICKNESS AND EFFECTIVE PARTICLE SIZE) BASED ON THE CALIPSO IIR MEASUREMENTS. THE FINAL ALGORITHMS, ALGORITHM COMPUTER CODES, AND RELEVANT DOCUMENTS WILL BE DELIVERED TO THE CALIPSO TEAM.