Leonard Hanssen is Project Leader for Infrared Spectrophotometry, and is responsible for the development and maintenance of NIST's scales for infrared spectral transmittance (τ), reflectance (ρ), and emittance (ε) of materials. His interests include the design and development of high accuracy measurement instrumentation, as well as the evaluation and optimization of absolute measurement methods, for τ, ρ and ε characterization. Of special interest are the theory, modeling, design, and application of integrating spheres; primarily for reflectance measurements, but also for creation of uniform Lambertian sources, and uniform detectors. He is also involved in collaborations concerning infrared detector metrology and infrared spectral radiance and radiance temperature metrology.
He is a member of the Society of Photo-Optical Instrumentation Engineers (SPIE), the Optical Society of America (OSA), the Council for the Optical Radiation Measurements (CORM), the ASTM International, and the American Geophysical Union (AGU).
He is the recipient of the Arthur S. Flemming Award in the area of Applied Science (2002), the Department of Commerce Silver Medal Award (2007), the NIST Judson C. French Award (2009), and the Department of Commerce Gold Medal Award (2013).