Patent ID: 7512505

Claim:
System for providing a common time base between different locations on earth, comprising: a first spacecraft (Sat 1 A) carrying a first component of a communication channel, wherein the position of said first spacecraft (Sat 1 A) is known, a plurality of receiving stations at different locations on earth, wherein each receiving station is adapted to receive a first reference signal from said first component, synchronisation means adapted to provide a synchronised time base between the plurality of receiving stations, and correction means adapted to correct the synchronisation error of the synchronised time base by the known position of the first spacecraft (Sat 1 A) and in accordance with the propagation time of each received first reference signal, wherein at least one receiving station comprises a correlation receiver yielding a correlation gain for receiving the first reference signal, wherein the first spacecraft transmits in a footprint, which is the coverage area of a payload signal, and wherein the correlation receiver recieves the first reference signal outside the footprint of the first spacecraft.