Development and operation of the Hemispherical Blackbody (HSBB) for the calibration of infrared radiometers with a hemispherical acceptance angle.

Longwave downward radiation measurements are fundamental for investigating the surface and atmospheric energy budget of the Earth. Such measurements are performed using broadband infrared radiometers that have a hemispherical acceptance angle. A new hemispherical reference blackbody has been developed to provide a new traceability path of longwave downward radiation measurements to the SI.