Lessons Leaned from Terra and Aqua MODIS SWIR Bands On-orbit Performance

The Moderate Resolution Imaging Spectroradiometer (MODIS) is currently operating on both the Terra and Aqua spacecrafts. As a major instrument for NASA's Earth Observing System (EOS) missions, the MODIS was designed to make continuous global observations using 36 spectral bands with wavelengths from visible (VIS), near-infrared (NIR), short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR) at three spatial (nadir) resolutions: 0.25km (bands 1-2), 0.5km (bands 3-7), and 1km (bands 8-36). Together the Terra and Aqua MODIS have accumulated nearly 10 years of science data sets, enabling a broad range of studies and research activities to be performed for the environment and climate changes. The MODIS has four SWIR bands with wavelengths centered at 1.24mm (band 5), 1.38mm (band 26), 1.62mm (band 6), and 2.1mm (band 7) with primary applications for the land/cloud and aerosol properties. They are located with six MWIR bands (20-25) on the same focal plane assembly, called the SMIR FPA. For Terra MODIS SWIR bands, large thermal leak (0.5-3 percent)and electronic crosstalk problems were identified from pre-launch calibration and characterization. Although a number of efforts have been made since then, including pre-launch hardware fix, on-orbit FPA configuration optimization, and the correction algorithms implemented in the Level 1B retrieval algorithm, remaining SWIR crosstalk effects still exist in a number of Terra MODIS science products. On the other hand, the Aqua MODIS SWIR bands have much smaller thermal leak and electronic crosstalk. Their on-orbit performance has been much better than that from Terra MODIS. In this paper we provide a description of MODIS SWIR bands thermal leak and crosstalk characterization, made at pre-launch and on-orbit, for both Terra and Aqua MODIS. We illustrate examples of the improvements made by the correction algorithms in the L1B, assess the effectiveness of the crosstalk reduction, and estimate the calibration uncertainties due to the remaining crosstalk effects. This study also serves as lessons learned for future sensors' design, pre- launch crosstalk characterization requirements, on-orbit validation methods, and correction limitation.