GPS receivers provide precise measurements of the TEC of the ionosphere and plasma sphere, revealing depletions associated with plasma bubbles and AGW perturbations as traveling ionospheric disturbances (TIDs). They detect amplitude and phase scintillations, and can also provide plasma density using inversion techniques. GPS receivers have proved to be a reliable, efficient, and practical way to measure line-of-sight TEC in several points of the sky simultaneously. This is the reason why the number of GPS units presently used for Aeronomy studies is 2000 or more on a worldwide basis. The observatory will include a densely distributed array of 50 GPS receivers to be sited in 10 different countries of South America.