ESA is proud to celebrate the excellent long-lasting performance of the Swedish-led Odin mission. Developed in collaboration with Canada, Finland and France, Odin reached its 18-year anniversary on 20 February 2019.

Odin is a Third Party Mission (TPM) and has been part of ESA's Earthnet Programme since 2007. As such, ESA is supporting the provision of Odin data to the international science community and researchers worldwide.

In summer 2019 Odin will also reach another milestone – 100,000 orbits around Earth. Giuseppe Ottavianelli, ESA TPM Manager states, "ESA is proud to support this international mission and its two instruments: the Swedish Sub-Millimetre Radiometer (SMR) and the Canadian Optical Spectrograph and InfraRed Imager System (OSIRIS). Despite its mature age, Odin is in good shape and continues collecting important atmospheric and long-term climate data."

Ottavianelli continues: "This milestone highlights the beneficial role of the ESA Earthnet Programme in facilitating these international collaborative efforts. Earthnet literally establishes the "Network for the Earth" capitalising on Member States national investments in Earth Observation and sharing EO knowledge and resources for the benefit of the European scientists and citizens".

The Odin satellite was designed and launched when ozone measurements were of special interest. After its launch in February 2001, Odin was in place to monitor a unique event when the ozone hole over the South Pole was split into two parts during a few days.

The long operational life of Odin has enabled collection of long time-series of various atmospheric data, thus contributing to climate relevant research. The older Odin gets, the more valuable the data sets, collected by its SMR and OSIRIS instruments, become.

The Sub-Millimetre Radiometer (SMR) monitors the composition of the middle atmosphere at altitudes of 15- 110 km, which is highly relevant for climate research. The data from the SMR instrument have been used in many international initiatives, dealing with measurements of ozone, water vapour and mesospheric trace gases. Moreover, SMR is currently the only instrument providing global measurements of nitric oxide, which is an important species to study the influence of the solar activity on the atmosphere. SMR observations have also contributed to a better understanding of sudden stratospheric warming events and of their effects on the coupling processes between different atmospheric layers.

The OSIRIS instrument provides high quality measurements of stratospheric nitrogen dioxide, ozone and sulphate aerosol and contributes to many important international initiatives. The vertically resolved profiles of these atmospheric constituents, derived from OSIRIS measurements, make up the longest currently produced data record and are therefore extremely valuable for investigation of long-term atmospheric change.

The OSIRIS ozone data makes valuable contributions to initiatives like SPARC (Stratosphere-troposphere Processes And their Role in Climate) and the Ozone Assessment of WMO, World Meteorological Organization. Similarly, the OSIRIS sulphate aerosol data record is essential to the GloSSAC (Global Space-based Stratospheric Aerosol Climatology) data record that is used as input to climate model studies that provide essential information that affect the Intergovernmental Panel on Climate Change Assessments.

The designed lifetime of Odin was two years. The fact that Odin is still in such a good condition after 18 years in orbit is due to several reasons. There is no fuel or other consumables on-board Odin, and the satellite is powered by solar energy. Odin has a sun-synchronous orbit, and solar activity has been rather low during the last solar cycle, thus the orbital altitude has not decayed as much as initially predicted. During the solar eclipse season, Odin is powered by two NiCd batteries. The batteries are kept in good shape by means of careful conditioning process before every eclipse season. Another positive aspect is that the main onboard computer has never been rebooted.

The Odin satellite was designed and built by the Space systems division of the Swedish Space Corporation, in collaboration with international partners. Currently, this division is part of the company OHB Sweden. Odin operations are under the responsibility of the Swedish National Space Agency.