Hans Joachim Liebe (21 January 1934 - 2 August 2012) was an internationally recognized expert in radio wave physics and developer of the widely-used Millimeterwave Propagation Model (MPM) . He was born in Insterburg, East Prussia, Germany, and graduated from the Technical University of Berlin in 1964 where he earned the Ph.D. degree in Electrical Engineering.
Dr. Liebe worked for the Institute for Telecommunications Sciences (ITS) in Boulder from 1966 until his retirement in 1995. Dr. Liebe was awarded the Senior U.S. Scientist Humboldt Award (1976), Department of Commerce Silver Medals (1984 and 1991) for meritorious service and outstanding publications, and the IEEE Harry Diamond Memorial Award (2002) for distinguished technical contributions in the field of millimeter wave propagation. Dr. Liebe was a Life Fellow of IEEE and a member of the US National Committee of International Union of Radio Science (USNC/URSI), Commissions A and F.
Dr. Liebe, over many years of continued study, developed reliable expressions for the complex refractivity of moist air that is basic to all millimeter and sub-millimeter wave propagation problems, inclusive of those in communications, navigation, and remote sensing. During the course of this model development, Dr. Liebe overcame many experimental difficulties and, to a large extent, verified the overlap between spectroscopic measurements and field measurements. His publications included basic studies of the absorption by gaseous water vapor and oxygen , as well as absorption by liquid water . In his thirty-year effort to obtain valid data on atmospheric loss and delay properties, he obtained a model that is highly accurate from RF frequencies up to approximately 1000 GHz. This model is in widespread use today in applications as diverse as weather forecasting, satellite broadcasting, and radar. Dr. Liebe’s work has been and remains vital to the remote sensing community, where almost all ground- and satellite-based microwave and millimeter radiometric techniques take advantage of his models. His more recent work on cloud absorption is also becoming increasingly important, as will the work on Zeeman splitting of the O2 absorption lines at mesospheric altitudes .
Dr. Liebe’s meticulous work and models are widely recognized throughout the global scientific community. He established a reputation for accurate measurements within 20 to 100 GHz well before commercial equipment was widely available in this range. He used spectroscopic theory to extend his estimates up to 1000 GHz, where there were very few reliable measurements available and at a time when very little quantitative knowledge of absorptive and refractive spectra was available in this spectral range. His work is nowadays the basis for remote sensing techniques currently being used for or considered for major airborne and spaceborne campaigns, including the geosynchronous microwave imager/sounder instrument and passive submillimeterwave cloud ice mass sensors. Dr. Liebe’s work constituted both outstanding science and a substantial contribution to radio wave propagation practice, as exhibited, for example, by the adoption of his work by the ‘International Telecommunication Union Study Group III of ITU-R’.
After his death, Roswita Liebe, his wife of 49 years funded the Hans Liebe Memorial Lecture which is given yearly in connection with the IEEE International Symposium on Antennas and Propagation.
 H. J. Liebe (1989), MPM: An atmospheric Mm-waves Propagation Model, Int. Journal of Infrarred an Millimeter waves, 10(6), 631-650.
 H. J. Liebe, Gimmestad, Hopponen (1977), Atmospheric oxygen microwave spectrum: experiment versus theory, IEEE Transactions on Antennas and Propagation, AP-25(3),327-335.
 H. J. Liebe, Hufford, Manabe (1991), A model for the complex permittivity of water at frequencies below 1 THz, Int. J. IR & MmWaves 12(7), 659-75.
 Hartmann, Degenhardt, Zwick, Liebe, Hufford, Cotton, Bevilacqua, Olivero, Langen, (MAS-team) (1996), Zeeman splitting of the 61 GHz oxygen line in the mesosphere, Geophys. Res. Lett., NASA-ATLAS 1 Mission, 23(17), 2329-32.