He is the project leader for infrared spectrophotometry in the Sensor Science Division of the Physical Measurement Laboratory.
Hanssen is responsible for the realizing and maintaining NIST's scales for spectral reflectance, transmittance, and emittance of materials at infrared wavelengths.
[2] Following the completion of his Ph.D., Hanssen worked at TRW Defense and Space Systems, Sachs Freeman Associates, and the Naval Research Laboratory.
[1] At NIST, Hanssen is responsible for realizing and maintaining the United States scales for infrared spectral reflectance, transmittance, and emittance of materials.
He manages the Fourier Transform Infrared Spectrophotometry (FTIS) Facility, which was developed to take low uncertainty measurements.