European Metrology Programme for Innovation and Research (EMPIR) project MetEOC3 - "Metrology for Earth Observation and Climate".
The overall aim of the project was to contribute to the establishment of the necessary metrology infrastructure for climate observing systems. This project was the follow-up of the EMRP MetEOC2 where Metrology Research Institute was contributing to collection of set of empirical data to support the building of bidirectional reflectance distribution function (BRDF) models for non-instrumented PICS as calibrations test sites and, in particular, for other than nadir observations.
In this project, Metrology Research Institute's main task was to measure BRDF of sand from Gobabeb test site that is one of the Radiometric Calibration Network (RadCalNet). This would produce a set of SI-traceable empirical data required to decrease the uncertainty of in-flight climate satellite calibrations.
For this purpose, Metrology Research Institute developed a 3D gonioreflectometer capable of in- and out-of-plane BRDF measurements of horizontally aligned samples . Coupling with a supercontinuum laser, two different detectors (Si and InGaAs) allow to operate the new instrument in the wavelength range from 450 nm to 1700 nm. SI-traceability of the 3D gonioreflectometer was achieved by measuring a spectralon PTFE sample, the BRDF of which had been characterised by an absolute reference gonioreflectometer with an uncertainty of 0.2%. Correction factors were derived from the ratio between absolute and relative spectralon BRDF measurements. The achieved relative standard uncertainty is between 0.5% and 1.2%, depending on the viewing zenith angle.
 Lanevski, D., Manoocheri, F. & Ikonen, E., “Gonioreflectometer for measuring 3D spectral BRDF of horizontally aligned samples with traceability to SI”, 1 Apr 2022, Metrologia 59, 025006, 13 pages (2022).
Contact persons: Farshid Manoocheri and Robin Aschan
More information can be found at the project website: