. Atmospheric remote sounding from satellites is an essential component of the observational strategy deployed to monitor atmospheric pollution and changing composition. The IASI nadir looking thermal infrared sounder onboard MetOp will provide 15 years of global scale observations for a series of key atmospheric species, with unprecedented spatial sampling and coverage. This paper gives an overview of the instrument's capability for measuring atmospheric composition in the perspective of chemistry and air quality. The assessment is made in terms of species, accuracy and vertical information. Global distributions are presented for CO, CH4, O3 (total and tropospheric), HNO3, NH3, and volcanic SO2. Local distributions of organic species measured during fire events, such as C2H4, CH3OH, HCOOH, and PAN are also shown. For each species or process, the link is made to specialized papers in this issue.

/pdf/monitoring-of-atmospheric-composition-using-the-thermal-2ktxqf7uy7.pdf

Monitoring of atmospheric composition using the thermal infrared IASI/METOP sounder

Abstract. Atmospheric remote sounding from satellites is an essential component of the observational strategy deployed to monitor atmospheric pollution and changing composition. The IASI nadir looking thermal infrared sounder onboard MetOp will provide 15 years of global scale observations for a series of key atmospheric species, with unprecedented spatial sampling and coverage. This paper gives an overview of the instrument's capability for measuring atmospheric composition in the perspective of chemistry and air quality. The assessment is made in terms of species, accuracy and vertical information. Global distributions are presented for CO, CH4, O3 (total and tropospheric), HNO3, NH3, and volcanic SO2. Local distributions of organic species measured during fire events, such as C2H4, CH3OH, HCOOH, and PAN are also shown. For each species or process, the link is made to specialized papers in this issue.

http://systemarchitect.mit.edu/docs/selva12b.pdf

A survey and assessment of the capabilities of Cubesats for Earth observation

Multi-decadal satellite measurements of global volcanic degassing

Intercalibration of satellite instruments is critical for detection and quantification of changes in the Earth's environment, weather forecasting, understanding climate processes, and monitoring climate and land cover change. These applications use data from many satellites; for the data to be interoperable, the instruments must be cross-calibrated. To meet the stringent needs of such applications, instruments must provide reliable, accurate, and consistent measurements over time. Robust techniques are required to ensure that observations from different instruments can be normalized to a common scale that the community agrees on. The long-term reliability of this process needs to be sustained in accordance with established reference standards and best practices. Furthermore, establishing physical meaning to the information through robust Systeme International d'unites traceable calibration and validation (Cal/Val) is essential to fully understand the parameters under observation. The processes of calibration, correction, stability monitoring, and quality assurance need to be underpinned and evidenced by comparison with “peer instruments” and, ideally, highly calibrated in-orbit reference instruments. Intercalibration between instruments is a central pillar of the Cal/Val strategies of many national and international satellite remote sensing organizations. Intercalibration techniques as outlined in this paper not only provide a practical means of identifying and correcting relative biases in radiometric calibration between instruments but also enable potential data gaps between measurement records in a critical time series to be bridged. Use of a robust set of internationally agreed upon and coordinated intercalibration techniques will lead to significant improvement in the consistency between satellite instruments and facilitate accurate monitoring of the Earth's climate at uncertainty levels needed to detect and attribute the mechanisms of change. This paper summarizes the state-of-the-art of postlaunch radiometric calibration of remote sensing satellite instruments through intercalibration.

/pdf/overview-of-intercalibration-of-satellite-instruments-4dsrud8mvp.pdf

Overview of Intercalibration of Satellite Instruments

The Infrared Atmospheric Sounding Interferometer (IASI) is a key payload element of the METOP series of European meteorological polar-orbit satellites. IASI will provide very accurate data about the atmosphere, land and oceans for application to weather predictions and climate studies. The IASI measurement technique is based on passive IR remote sensing using an accurately calibrated Fourier Transform Spectrometer operating in the 3.7 - 15.5 μm spectral range and an associated infrared imager operating in the 10.3-12.5 μm spectral range. The optical configuration of the sounder is based on a Michelson interferometer. Interferograms are processed by the on-board digital processing subsystem which performs the inverse Fourier Transform and the radiometric calibration. The integrated infrared imager allows the co registration of the IASI sounder with AVHRR imager on-board METOP.
The first model (proto-flight) of IASI has successfully completed a verification program conducted at ALCATEL SPACE premises in Cannes. This paper provides a brief overview of the IASI mission, instrument architecture and key performances results. A companion paper1 by Alcatel provides more information on instrument design and development.

IASI instrument: technical overview and measured performances

The Infrared Atmospheric Sounding Interferometer (IASI) is a key element of the payload embarqued on METOP series
of European meteorological polar-orbit satellites. IASI will provide very accurate data about the atmosphere, land and
oceans for application to weather predictions and climate studies. IASI measurements will allow to derive temperature
and humidity profiles with a vertical resolution of one kilometer and an average accuracy of one Kelvin and 10 %
respectively. The IASI measurement technique is based on passive IR remote sensing using a precisely calibrated
Fourier Transform Spectrometer operating in the 3.7 - 15.5 μm region and an associated infrared imager operating in the
10.3-12.5 μm region. The optical configuration of the sounder is based on a Michelson interferometer. Interferograms
are processed by the onboard digital processing subsystem which performs the inverse Fourier Transform and the
radiometric calibration. The integrated infrared imager allows the coregistration of the IASI soundings with AVHRR
imager onboard METOP. The first METOP satellite was successfully launched on 19th of October 2006. This paper
summarizes the IASI instrument radiometric, spectral and geometric performance as measured in orbit during the
Calibration and Validation Phase. Instrument noise, spectral and radiometric calibration stability and spatial pointing
accuracy are discussed as well as the performance of the Level 1 Processing chain.

In-flight performance of the infrared atmospheric sounding interferometer (IASI) on METOP-A

IASI was successfully launched on MetOP A on 19 October 2006. After the in-orbit commissioning, the performances
of IASI were evaluated during the Cal/Val of level 1. Key parameters of instrument and on ground processing have been
fixed for optimal performance and best quality data delivery. The first spectra and images of level 1 products show all
the potential of IASI data for expected applications. Some illustrations are given here with maps of pseudo channels
sensitive to trace gases, atmospheric profiles or maps of surface temperature qualitatively compared to maps from
models. Level 2 processing to get these parameters has been implemented at Eumetsat and some products are currently
under validation. The quality of IASI data paves the way to additional very promising products. A thorough analysis of
cloud free spectra has been performed to extract the small signature of minor species like CFCs and HNO3. Nevertheless,
the main limitation of IASI data remains clouds. It is showed here with the cluster analysis of AVHRR data registered in
the IASI pixels and delivered as level 1 products that only a few cloud free pixels can used for full retrieval. A method
making use of the cluster information has been developed. It permits to strongly increase the statistics where clear
column profiles or columns above clouds can be retrieved. This scheme will be applied to the retrieval of the CO2 where
large data set are needed to extract information from the spectra.

Applications of IASI on MetOp-A: first results and illustration of potential use for meteorology, climate monitoring, and atmospheric chemistry

One way to calibrate space sensors on the visible part of the spectrum is to use acquisitions over Rayleigh scattering for
dark surface conditions. Oceanic sites are good candidates because of their behaviour in term of spatial homogeneity and
temporal stability. An appropriate selection is consequently required to identify the best oceanic areas. Nevertheless, the
knowledge of the surface reflectance of such sites remains a limitation while their stability (and/or homogeneity) is
usually not perfect. A previous study (Fougnie et al., 2002) has defined a selection of oceanic sites using one year of
SeaWiFS data and regarding their spatial homogeneity and temporal stability. A first characterization of their monthly
surface reflectances was derived (seasonal cycle) and used for several years as input for in-flight calibration processes.
The major oligotrophic sites are located in North/South Atlantic and Pacific oceans, in Indian ocean, and in the
Mediterranean Sea while some other mesotrophic sites were also defined for example in the Gulf of Mexico or Yucatan
strait. The goal of this study was to revisit the definition of these sites regarding their spatial homogeneity and to analyze
the annual cycle over 9 years of L3B R-2009 SeaWiFS products. Site behaviours are accurately defined with these
longer time series, hence new recommendations are drawn for all sites and an updated climatology is proposed to be used
for future in-flight calibrations.

Climatology of oceanic zones suitable for in-flight calibration of space sensors

IASI is an infrared atmospheric sounder. It will provide meteorologist and scientific community with atmospheric spectra. The IASI system includes 3 instruments that will be mounted on the Metop satellite series, a data processing software integrated in the EPS (EUMETSAT Polar System) ground segment and a technical expertise centre implemented in CNES Toulouse. The instrument is composed of a Fourier transform spectrometer and an associated infrared imager. The optical configuration is based on a Michelson interferometer and the interferograms are processed by an on-board digital processing subsystem, which performs the inverse Fourier transforms and the radiometric calibration. The infrared imager co-registers the IASI soundings with AVHRR imager (AVHRR is another instrument on the Metop satellite). The presentation will focus on the architectures of the instrument, the description of the implemented technologies and the measured performance of the first flight model. CNES is leading the IASI program in association with EUMETSAT. The instrument Prime is ALCATEL SPACE.

/pdf/iasi-instrument-technical-description-and-measured-1tfpntsdt4.pdf

Denis Blumstein

Papers

IASI instrument: technical overview and measured performances

In-flight performance of the infrared atmospheric sounding interferometer (IASI) on METOP-A

Applications of IASI on MetOp-A: first results and illustration of potential use for meteorology, climate monitoring, and atmospheric chemistry

Climatology of oceanic zones suitable for in-flight calibration of space sensors

IASI instrument: technical description and measured performances