Published: August 09, 2011
Satellite image of the ash cloud from the Puyehue eruption (at left edge) moving east/north-east across Argentina towards the Atlantic. (Source: NASA Earth Observatory).
The most recent eruption of the Chilean volcano Puyehue began on June 4, 2011, and produced an ash plume that rose to an altitude of 10 km. Among other problems, it severely disrupted air traffic, first over large areas of South America and then in Australia and New Zealand as well. The ash cloud was observed and measured by devices such as the European weather satellite MetOp-A, which has an infrared atmospheric sounding interferometer (IASI) as its major equipment. The IASI is a measurement instrument that provides very precise, vertically resolved data on the constituents of the atmosphere. One of its main components is a mirror that moves periodically, generating an interference pattern from which the required atmospheric data can be derived. The mirror's control system was developed with the aid of a dSPACE system consisting of a DS1005 board and other components. Precision was one vital requirement for the mirror control system, and absolute reliability was another, because if a fault occurs in orbit, it is not possible to repair it. MetOp-A was launched in 2006 as the first of three MetOp satellites that are being placed in low-earth, polar orbits at intervals of several years to provide continuous atmospheric data until the year 2020.