This paper describes a measurement method for characterizing the reflectivity of blackbodies used as calibration devices in spaceborne instruments. The fundamental measurement principle is based on the scattering matrix theory. A monostatic apparatus has been developed to implement the reflectivity measurements up to 220 GHz. A few blackbody emitters made of metamaterials were measured at a number of radiometric frequencies. The results demonstrated the feasibility of using metamaterial blackbodies on miniaturized satellite platforms.

In this work, we present metamaterial-based microwave absorbers fabricated on organic-based printed circuit boards as promising alternatives to traditional, bulky microwave absorbers for the calibration of microwave radiometers for atmospheric remote sensing. Their use is particularly attractive for onboard calibration of sensors on CubeSats and other small satellites. Planar metamaterials can be fabricated with near-unity absorption over a very broad frequency range, and are scalable by tuning the unit cell geometry. Specifically, we describe an approach and initial measurements toward designing a broadband metamaterial emitter operating at millimeter wave sounding channels from 50 GHz 230 GHz, enabling a thin, cost-effective calibration target for millimeterwave atmospheric remote sensing.