IASI

The main goal of the IASI mission is to provide temperature and humidity profiles for use in the understanding and making atmospheric forecasts.

IASI image, from CNES, large

The Infrared Atmospheric Sounding Interferometer IASI represents a significant advance in the quality of the measurements injected into meteorological models. It uses original technologies for a new European contribution to polar meteorology.

IASI Summmary Budget

What is IASI?

The concept of IASI is based on the spectral decomposition of thermal heat emission from the Earth, performed with a Michelson interferometer.

After an inverse digital Fourier transform and radiometric calibration, performed on board to control data flow, the calibrated spectra are transmitted to the ground sector.

After the data inversion, temperature and water vapour profiles in the troposphere and lower stratosphere are established, as well as the quantification of atmospheric chemical components — such as ozone, carbon dioxide and methane — that play a basic role in tropospheric phenomena and the greenhouse effect.

The temperature of the troposphere and lower stratosphere is measured under cloud-free conditions with a vertical resolution of 1 km in the lower troposphere; a horizontal resolution of 25 km, and an accuracy of 1 kelvin.

A graphic showing the field of view of IASI

The humidity of the troposphere is measured under cloud-free conditions, with a vertical resolution of 1–2 km in the lower troposphere; a horizontal resolution of 25 km, with an accuracy of 10%.

IASI also measures the fractional cloud cover and cloud top temperature and pressure.

The total amount of ozone under cloud-free conditions is measured with a horizontal resolution of 25 km and an accuracy of 5%, and total column-integrated content of CO, CH4 and N2O with an accuracy of 10% and a horizontal resolution of 100 km.

The IASI programme is led by CNES in association with EUMETSAT. Alcatel Alenia Space is the instrument Prime Contractor. For more in-depth information, see the IASI Level 1 Product Guide (PDF, 3 MB).

IASI Summary Budgets
Scan Rate 8 secs
Scan Type Step and dwell
Pixel IFOV 0.8225°
IFOV size at Nadir S12 km
Sampling at Nadir 18 km
Earth View Pixels/Scan Two rows of 60 pixels each
Swath ± 48.98°
Swath ± 1066 km
Spectral Range 645 to 2760 cm-1
Spectral Sampling 0.25 cm-1
Lifetime Five years
Power 210 W
Size 1.2 m x 1.1 m x 1.3 m
Mass 236 kg
Data rate 1.5 Mbps