Since the launch of the second Metop platform in September 2012, two IASI (Infrared Atmospheric Sounding Interferometers) instruments are flying on the same orbit, overflying the same area with 50 minutes delay. This provides a unique opportunity to perform multiple inter-comparisons and cross-monitoring. To do so, different methodologies have been implemented to provide complementary results giving qualitative and quantitative information on the instruments in terms of radiometric and spectral inter-calibration. This includes in particular comparisons between IASI and other infrared instruments. In this paper we will present an overview of the comparison that have been performed between IASI and the High-resolution Infrared Sounder (HIRS) flying on the same platform as well as comparisons with the Cross-track Infrared Sounder (CrIS) flying on Suomi-NPP. This monitoring which, besides giving confidence on the intercalibration of both IASI, provides a way to detect the slightest differences between IASI and other infrared multispectral instruments.
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