Spectral emissivity measurements gathered in the longwave infrared region of the spectrum during a recent airborne hyperspectral data collection experiment indicated that the spectral emissivity of certain organic polymers changed by as much as 10% throughout the day. Inorganic and many other organic materials that were measured at the same time during this experiment showed no change. As this was an unexpected event, a subsequent experiment was designed to make emissivity measurements of several organic and inorganic materials over a 24-hour period/diurnal cycle. The results from this experiment confirmed that certain materials showed a significant spectral emissivity variation over this period. This paper will discuss some possible explanations for this variation and emphasize the significance and implications of this fact on the integrity of spectral emissivity measurements and spectral libraries being constructed in this wavelength region.

Publication Date



"Temporal variations in the apparent emissivity of various materials," Proceedings of the SPIE, Sensor Data Exploitation and Target Recognition, Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery X, Vol. 5425. The International Society of Optical Engineers. Held in Orlando, Florida: April 2004. This paper is made available as an electronic reprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Special thanks need to be given to Herbert J. Mitchell for his contributions to this work. His perseverance and drive to understand physical phenomenology are inspiring and make us all ask the questions that need to be asked when making optical properties measurements. The authors would also like to thank the National Geospatial-Intelligence Agency (NGA), the National Air & Space Intelligence Center (NASIC), and the Rochester Institute of Technology for their support and/or sponsorship for these studies.ISSN:0277-786X Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type


Department, Program, or Center

Chester F. Carlson Center for Imaging Science (COS)


RIT – Main Campus