Interferometric monitor for greenhouse gases (IMG)

Interferometric monitor for greenhouse gases (IMG)

Table of contents

1. Introduction
2. Working principle
3. Sensor details
4. Applications
5. Sources

Physics for sensor technology

Metropolia UAS

Group B

Timo Lummukka, Vadim Amirov, Jaakko Kontkanen, Jaffry Salman

Introduction

Growing awareness on climate change has created an increasing interest to observe concentrations of gases contributing to the warming of the climate. A specially effective way of doing this is to observe this from space, as this enables to an excellent spatial coverage of earth on the flight path of the satellite. Necessary technologies had been unlocked and thus a joint co-operative was launched to create a sensor suitable for the task.

Interferometric monitor for greenhouse gases (IMG) is a satellite born sensor based on FTIR developed in co-operation by JAROS, NASDA and NASA. IMG measured upwelling infrared radiance at fine spectral resolutions. The instrument was designed to have a very high spectral resolution (0.05 cm).The sensor will obtain very accurate spectra of of the thermal infrared radiation from the atmosphere and this data can be used deduce concentrations of greenhouse gases and water vapour.

In the IMG, the light coming from the surface of Earth and clouds is compared to the light from the Helium - Neon laser (He-Ne laser).

1. http://suzaku.eorc.jaxa.jp/GLI2/adeos/Project/images/img-fig2.gif

Working principle

• Interferometry
• Fourier-transform infrared spectroscopy

Interferometry:

Interferometry is a study of wavelenghts, light and interfernce (Hence the name). The usual component to study is electromagnetic radiation.  Waves are superimposed, meaning they are manipulated in a way to give some meaningful analytical results. Usually light is used as the source of the electromagnetic waves.

The basic principle of a Michelson - interferometer: A light is introduced into the system and it is manipulated to travel two different paths. The paths are then guided to meet at a point (The detector). The difference in the path travelled creates an interference pattern and this pattern can be studied and interpreted. This yields e.g.  a refractive index which can be purposefully understood.

A schematic of a michelson interferometer

2. http://cnx.org/content/m22326/latest/graphics2.jpg

Sensor details

Detection and monitoring of the vertical and spatial distribution of:

• CO2
• CH4
• O3
• Nitrogen based molecules (N2O, NO2)
• CFC

Applications

IMG has been deployed on atleast two occasions.

1. ADEOS 1 (Advanced Earth Observing Satellite): launched in 1996 and flew in the polar orbit.
2. ADEOS 2: launched in 2002

Sources

1. http://www.sciencedirect.com/science/article/pii/S0273117799009266 (Accessed 15.4.2014)
2. http://www.webpages.uidaho.edu/~vonw/pubs/WaldenEtAl_2010.pdf (Accessed 15.4.2014) (Continue here Timo)
3. http://suzaku.eorc.jaxa.jp/GLI2/adeos/Project/Img.html