um artigo interessante:
10 GPS Vulnerabilities
by Lieutenant Colonel Thomas K. Adams, US Army, Retired
For centuries explorers have navigated by fixed stars. Today our increasingly expeditionary military navigates by orbiting emitters. Satellites enable flexible communication and precise navigation that were unimaginable a generation ago. Space-based technologies reach down into everyday military business so much that interrupted service immediately and fundamentally degrades operations. Adams describes various threats to US satellites, systems that use their signals and a military that depends on falling stars.