The innovative feature of the Odin mission is that it splits observation time equally between aeronomy and astronomy science objectives. For CNES and the French national scientific research centre CNRS, the mission plays into a set of programmes aimed at improving our knowledge of the processes at work in the Earth system and the Universe.
The aeronomy objective of Odin’s mission is to track variations in stratospheric ozone and in particular the polar ozone “hole” that forms every year. After the Montreal protocol in 1987 and a series of amendments designed to regulate emissions of ozone-depleting chlorofluorocarbons (CFCs), models now predict a return to pre-industrial ozone levels by the middle of this century. But model scenarios need to be validated by observations to verify what we know.
Odin’s astronomy objective is to conduct observations impossible from the ground at wavelengths blocked out by Earth’s atmosphere. It therefore aims to tell astronomers more about the physical and chemical processes going on in the interstellar medium and in the atmospheres of comets and other planets, and shed new light on star-forming regions inside cold interstellar clouds.
Odin is a technological feat made possible by successful cooperation between four national space agencies: the Swedish National Space Board (SNSB), the Centre National d’Études Spatiales (CNES), the Canadian Space Agency (CSA) and the National Technology Agency of Finland (NTAF).
Odin’s payload consists of two innovative instruments:
- the Sub-Millimetre Radiometer (SMR) is the first instrument to operate in the microwave domain at frequencies of 485 to 580 GHz to acquire measurements from space of a range of atmospheric molecules, among them ozone (O3), molecular oxygen (O2), chlorine monoxide (ClO), water vapour (H2O) and isotopes (HDO, H218O), nitrous oxide (N2O), nitric acid (HNO3), ammonia (NH3) and carbon monoxide (CO);
- the Optical Spectrograph and InfraRed Imager System (OSIRIS), operating in the ultra-violet, visible and infrared, is the first instrument to systematically observe sunlight scattered by the Earth’s limb to measure concentration profiles of ozone and nitrogen dioxide (NO2) in the middle atmosphere.
A number of laboratories from the four partner nations worked on designing these two instruments, built by various industrial manufacturers, and have been exploiting the science data obtained since the summer of 2001. They are:- the LESIA space and astrophysics instrumentation research laboratory, and the LERMA astrophysical radiation and matter research laboratory, affiliated to the Observatoire de Paris;- the LAM astrophysics laboratory, affiliated to the Marseille-Provence astronomy observatory;- the CESR space radiation research centre, affiliated to the Observatoire de Midi-Pyrénées;- the L3AB astrodynamics, astrophysics and aeronomy laboratory in Bordeaux, the aerology laboratory at the Observatoire de Midi-Pyrénées and the SA aeronomy laboratory at the Institut Pierre Simon Laplace (IPSL), which are studying Earth’s atmosphere.
We conclude with a tribute to three people no longer with us who were instrumental in making Odin a scientific and engineering success: Gérard Mégie at Pierre et Marie Curie University, French leader of the Odin aeronomy team, founder and first director of IPSL, President of CNRS and President of the CNES Science Programmes Committee from 2002 to 2004; Guy Serra, CNRS and CESR research director, a pioneer of infrared and sub-millimetre satellite astronomy; and Frédéric Bonneau, CNES engineer.
Christiane Grappin, phone 33 1 44 96 43 37 – 33 6 82 68 60 24
Sandra Laly, phone 33 1 44 76 77 32 – 33 6 08 48 39 31