* Astronomy

There is no evidence for recovering ozone layer yet, according to the latest results from the Odin satellite.

The Odin satellite is now celebrating five years of observations.

The Swedish orbital observatory Odin confirms large natural variations of ozone depletion processes over the poles, now five years since its launch on February 20, 2001. Odin is the only satellite to have made continuous measurements of the chlorine chemistry in the ozone layer since 2001. Although helpful in global mapping of these processes, a few years of observations is not enough to distinguish global change - recovering ozone layer or not - from the large natural variations. Prolonged observations should help in resolving this issue. Fortunately, there is good hope that Odin can provide such observations for years to come since the satellite still is fully functional.

Odin has also confirmed that the transport of air in the stratosphere from the equator to the poles is slower than in currently used models. Correct models are needed to make prognoses, for instance about how the ozone layer will recover. Further Odin observations related to climate regard noctilucent clouds over the poles and of ultra-thin clouds over the equator, invisible to the eye. The effect of solar particles on water vapour and temperature in he upper atmosphere is also studied. Here again, observations during a long time are important, to cover a major part of the eleven-year solar activity cycle.

Odin data are used as references by both ESA and NASA validating new instruments in space and for other international measuring campaigns in the atmosphere. During the International Polar Year 2007, several European research projects are based on the continued use of Odin data. Monitoring chemistry and transport of the upper atmosphere makes Odin a suitable forerunner to the atmospheric part of the proposed European system for environmental surveillance, GMES.

Odin has the double mission to support both astronomical and atmospheric research. The main instrument, a sub millimetre radiometer (SMR) is used for both disciplines and is for atmospheric measurements complemented by an optical spectrograph and infrared imager (OSIRIS). The combination of the SMR and OSIRIS instruments makes Odin well adapted for atmospheric studies of higher altitudes.



In order to fulfil the scientific requirements Odin is 3-axis stabilised, capable of switching between astronomy and aeronomy modes. It can be staring at astronomical targets for hours with an accuracy of 15 arc seconds or can scan the limb of the Earth's atmosphere at various speeds between 10 and 120 km altitudes, 40 times per orbit, with a reconstructed accuracy of 1.2 arc minutes. The entire satellite is pointed towards the targets.
Odin was placed into a 600 km sun-synchronuous, terminator orbit by a START-1 rocket from Svobodny, far eastern Russia.

The satellite is operated from a ground station at Esrange. The nominal life time is 2 years.

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