Laboratory test simulation for non-flat response calibration of global Earth albedo monitor

In this report, we present laboratory test simulation for directional responsivity of a global Earth albedo monitoring instrument. The sensor is to observe the Sun and the Earth, alternately, and measure their shortwave (<4Îm) radiations around the L1 halo orbit to obtain global Earth albedo. The instrument consists of a broadband scanning radiometer (energy channel instrument) and an imager (visible channel instrument) with ±2°field-of-view. In the case of the energy channel instrument, radiations arriving at the viewing ports from the Sun and the Earth are directed toward the pyroelectric detector via two spherical folding mirrors and a 3D compound parabolic concentrator (CPC). The instrument responsivity is defined by the ratio of the incident radiation input to the instrument output signal. The radiometers relative directional responsivity needs to be characterized across the field-of-view to assist output signal calibration. For the laboratory test, the distant small source configuration consists of an off-axis collimator and the instrument with adjustable mounts. Using reconstructed 3D CPC surface, the laboratory test simulation for predicting the instrument directional responsivity was conducted by a radiative transfer computation with ray tracing technique. The technical details of the laboratory test simulation are presented together with future plan.