Interestingly, Brazil finally ordered a very advanced radar system from the US to keep the Amazon under observation:
"U.S. awareness of the area further increased in 1994, when the Raytheon corporation (famous for its Patriot missiles employed during the Gulf War) was awarded a $1.4 billion dollar contract to build a radar system. This in itself is hardly surprising, given the company's record of building similar facilities for the U.S. Navy, particularly the highly controversial "over the horizon" system (ROTHR) being deployed on the Puerto Rican island of Vieques. The curious note was that the call for bids had issued from Brazil, which was interested in creating an advanced radar network within Amazonia to be known as SIVAM."
I posted a thread about SIVAM on ATS in 2005.
If Brazil can detect UFO's, So can the U.S.!!!