ILRS Mission Support Status: Satellite Laser Ranging (SLR) tracking support of this satellite was discontinued in October 1998. What makes Meteor-2-21 distinctive from the other meteorological satellites is its unique retroreflector array. The name "Fizeau" is derived from a French physicist, Armand Fizeau who, in 1851, conducted an experiment which tested for the aether convection coefficient. SLR tracking of this satellite was used for precise orbit determination and the Fizeau experiment. The Fizeau experiment tests the theory of special relativity – that distance events that are simultaneous for one observer will not be simultaneous for another observer who is in motion relative to the first observer.