The IASI programme is composed of three instruments mounted on three successive METOP satellites the first launched in 2006, the others scheduled for 2012 and 2018. The instrument is designed for acquiring continuously atmosphere spectra and images with a data rate of 1.5 Mbits/s. Its nominal working will be interrupted only for operations allowing to maintain the performance (modifications of data processing parameters, decontamination of radiator and optics, etc.).
IASI is a spectrometer, i.e. an instrument which measures the spectral distribution of the radiation. The instrument concept is based on the Michelson interferometer. This concept was validated by CNES on a laboratory breadboard.
The main characteristics are defined in order to meet the mission requirements and to be compliant with the satellite capabilities. In particular, the spectral resolution and the radiometric resolution deal with the retrieval of temperature and humidity profile with a vertical resolution of one kilometre and accuracies of one kelvin and 10% respectively.
Due to height performance requirements, innovative technical solutions and technologies are used to build the instrument components.
The IASI instrument comprises an on-board management unit and a digital processing subsystem which performs the inverse Fourier transform and the radiometric calibration. It includes also an infrared imager.