IASI-A

IASI-A is the first model of the IASI instrument series developed by CNES in cooperation with the European Organisation for the Exploitation of Meteorological Satellites (Eumetsat). Its two main missions are operational meteorology and atmospheric chemistry. It is a Fourier transform infrared spectrometer that provides luminance spectra of the atmosphere and derived atmospheric variables.

IASI-A is on board the Eumetsat Metop-A satellite.

Satellite

Metop-A was launched on October 19, 2006 from the Baikonur Cosmodrome in Kazakhstan. It was declared operational on July 18, 2007. It is the first model of the Eumetsat MetOp series.

METOP-A orbit parameters:

• Near-circular sun-synchronous polar orbit
• Mean altitude: 817 km
• Inclination: 98.7°
• Local solar time at equator (descending node): 9h30
• Cycle: 29 days (412 orbits)

From October 2012, it flew in tandem with MetOp-B, shifted by half an orbit (in phase opposition on the same orbit). Then, at the beginning of 2017, the decrease in the amount of propellant available on board led to stop the satellite’s inclination correction manoeuvres, leading to a slow drift of the orbit.
This orbital drift has led to a progressive drift of the local time of crossing the equator until 7.30 a.m. in September 2021.

In addition to IASI, the meteorological core payload comprises several other instruments dedicated to the operational meteorology and climate monitoring: AMSU-A, ASCAT. AVHRR, GOME-2, GRAS, HIRS/4, MHS.

Instrument

The 3 IASI-A, IASI-B and IASI-C instruments are identical.

Products

IASI-A products available at AERIS

• Vertical profile (level 2) and total column-integrated content of CO (level 2 and level 3)
• Total column-integrated content of HCOOH (level 2 and level 3)
• Total column-integrated content of NH₃ (level 2 and level 3) – near real time and reanalysis
• Vertical profile (level 2) and total column-integrated content of O₃ (level 2 and level 3)
• Total column-integrated content of SO₂ and plume altitude (level 2)
• Mid-tropospheric column of CH₄ (level 2)
• Dust Aerosol Optical Depth and mean layer altitude (level 2)
• Clouds temperature, pressure, type, emissivity and height (level 2)

The IASI/GOME2 processing for ozone retrieval is not applied to IASI A data.