The new satellite instrument, IASI (Infrared Atmospheric Sounding Interferometer), is a moderate resolution (0.25 cm-1) Fourier Transform spectrometer launched in 2002 on the European METOP satellite. This instrument offers more spectral channels at a considerably higher spectral resolution than HIRS (High Resolution Infrared Sounder) - the instrument which it replaced as the operational infra-red sounder. IASI delivers vertical profiles of temperature and humidity data with a resolution of 1km compared with approximately 4km from HIRS.

Translating the improvement in the spectral resolution of the instrument into improvements in the accuracy and height resolution of the temperature, humidity and ozone profiles is dependent on a detailed knowledge of the spectroscopy of the atmosphere in this spectral region. The aim of the Validation of IASI (Infrared Atmospheric Sounding Interferometer) Radiative Transfer Experiments and Modelling (VIRTEM) project was to make the improvements to the spectroscopy necessary to make full use of the increased spectral resolution of IASI.

The primary objectives of the VIRTEM project were:

*To generate a detailed set of atmospheric observations of radiances and supporting in-situ data.
*To analyse and validate the current spectroscopy using state of the art line-by-line radiation models.
*To generate an improved spectroscopic database.

VIRTEM was an EU project to validate the instrumentation and retrieval methods to be used on IASI. Data in this dataset collection include both aircraft based and lab based spectroscopic measurements.