The MODIS Flight Model 1 (FM1) has been in operation for more than two years since its launch onboard the NASA's Earth Observing System (EOS) Aqua spacecraft on May 4, 2002. The MODIS has 36 spectral bands: 20 reflective solar bands (RSB) with center wavelengths from 0.41 to 2.2mm and 16 thermal emissive bands (TEB) from 3.7 to 14.5mm. It provides the science community observations (data products) of the Earth's land, oceans, and atmosphere for a board range of applications. Its primary on-orbit calibration and characterization activities are performed using a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) system for the RSB and a blackbody for the TEB. Another on-board calibrator (OBC) known as the spectro-radiometric calibration assembly (SRCA) is used for the instrument's spatial (TEB and RSB) and spectral (RSB only) characterization. We present in this paper the status of Aqua MODIS calibration and characterization during its first two years of on-orbit operation. Discussions will be focused on the calibration activities executed on-orbit in order to maintain and enhance the instrument's performance and the quality of its Level 1B (L1B) data products. We also provide comparisons between Aqua MODIS and Terra MODIS (launched in December, 1999), including their similarity and difference in response trending and optics degradation. Existing data and results show that Aqua MODIS bands 8 (0.412mm) and 9 (0.443mm) have much smaller degradation than Terra MODIS bands 8 and 9. The most noticeable feature shown in the RSB trending is that the mirror side differences in Aqua MODIS are extremely small and stable (<0.1%) while the Terra MODIS RSB trending has shown significant mirror side difference and wavelength dependent degradation. The overall stability of the Aqua MODIS TEB is also better than that of the Terra MODIS during their first two years of on-orbit operation.
The Moderate Resolution Imaging Spectroradiometer (MODIS) is an Earth-viewing sensor that is currently operating on the EOS-Terra and EOS-Aqua satellites. Each MODIS instrument has 36 bands. Data are received from 490 detectors in these reflective Solar and infrared emissive bands. Calibration of the 490 channels on each MODIS instrument is performed by the MODIS Characterization Support Team (MCST), which works closely with the members of the MODIS Science Team to provide a calibration product that is useful for their geophysical products. The MODIS Level 1B (L1B) algorithm performs radiometric calibration for the duration of each mission. The L1B input files, output data products, and the emissive and reflective calibration algorithms are described. The Look-up Tables (LUTs) that provide the instrument characterization needed to run the L1B software are also described. We briefly present the L1B code standards, properties, and enhancement process. Lastly, "lessons learned" are discussed.