Terra and Aqua MODIS calibration algorithms and uncertainty analysis

Abstract

NASA's Earth Observing System (EOS) Terra spacecraft was launched in December 1999 and the Aqua spacecraft in May 2002. The Moderate Resolution Imaging Spectroradiometer (MODIS) is one of the key instruments for NASA's EOS missions, currently operated on both the Terra and Aqua spacecrafts. Together they have made continuous global observations for more than 8 years and led to many applications and studies for the Earth's system of land, oceans, and atmosphere. Compared to its heritage sensors, the MODIS was designed with more stringent requirements on the sensor's calibration accuracy and data product quality. Because of this it is equipped with a set of on-board calibrators (OBCs), including a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) for the reflective solar bands (RSB) calibration and a blackbody (BB) for the thermal emissive bands (TEB) calibration. In addition to the sensor's intrinsic design characteristics, the quality of MODIS data products depends on the quality of its on-orbit calibration and characterization and on its on-orbit performance. The primary objective of this paper is to provide an overview of MODIS on-orbit radiometric calibration approaches and a summary of the calibration uncertainties for both RSB and TEB (Terra and Aqua). This paper provides an update to our previous reports with considerations based on each sensor's characteristics identified pre-launch, measured and validated on-orbit. It also serves as a useful reference for the users of MODIS data products.