Complex sentence: MEOSAR consists of SARR transponders aboard the following navigation-satellite constellations: the European Union's Galileo, the Russian Federation's Glonass and the United States' Global Positioning System (GPS).
Split into simpler sentences: MEOSAR consists of SARR transponders aboard navigation satellites of the European Union, the Russian Federation and the United States. Those satellite constellations are Europe's Galileo, the Russian Federation's Glonass and the United States Global Positioning System (GPS).