There are currently several thermal infrared remote sensing instruments in operation, with different instrumental designs, driven by specific science objectives. For tropospheric chemistry studies this includes the nadir-looking AURA instruments such as Mopitt, TES and AIRS as well as the Infrared Atmospheric Sounding Interferometer (IASI) launched at the end of 2006 onboard MetOp satellite. The latter has the advantage as an operational mission supporting Numerical Weather Predictions of a relatively high spatial resolution (12 km footprint at nadir) and high spatial and temporal sampling. This presentation gives a short overview of the IASI achievements for tropospheric composition monitoring after 3 years of operation, with highlights of comparisons/complementarities with Mopitt, TES and AIRS, and discussion of the long-term plans for IASI-like missions after 2020.