More detailed data
Glass ceramic from Scott is also on board
Such an outstanding image quality requires high-performance mirrors. The mirrors used in the SEVIRI were made from “ZERODUR®” glass ceramic. This material has a thermal expansion near zero and therefore remains dimensionally stable even when exposed to strongly varying temperatures. It can be polished like optical glass, which means that it is possible to obtain extremely smooth surfaces. Carl Zeiss, Oberkochen, took care of fine polishing the mirrors for the SEVIRI. In addition, the glass ceramic can be structured with the help of milling and etching processes so that the total weight of a component can be reduced by up to 85 percent.
In the case of the plane mirror, however, SCHOTT reduced the weight by just 70 percent. The orbit of the satellite is stabilized by the fact that it rotates around its axis 100 times per minute. If the mirror were too lightweight, it would not be able to withstand the oscillations and vibrations.
The MSG-1 satellite is designed to provide data for more exact and more reliable weather forecasts – initially for seven years. However, to ensure that data transmissions continue without interruption, three additional satellites of the same construction are planned. MSG-2 is scheduled to follow MSG-1 in just 18 months; it will be kept on “standby” in a reserve orbit. MSG-3 will then be launched at the end of the service life of the first satellite so there will always be two satellites in orbit and ready for action. The fourth MSG satellite is currently under construction. MSG-4 will guarantee the mission until the end of the next decade.