Document Type : Research Paper

Author

• Abbasali Salehabadi

Abstract

On March 25, 1989, the US Department of Defense confirmed great fear of the civil users of GPS while S.A is activated. What S.A does is damaging and degrading the precision of GPS signals in order to prevent GPS users from gaining access to this system’s high precision. Experts state that S.A has
less impact on surveying applications than other GPS applications.
When S.A is on, It disrupts satellite data, which occurs through falsifying of satellite clocks and orbital information. Indeed, according to Dr. Javad Ashjaei, head of the “Ashtek and colleagues” Corporation., S.A. will add to the GPS signals’ noises. In fact, signals move forward, backward or around. S.A. falsifies signals to the extent that they report a problem in the orbit of satellites. "S.A only affects the Bloom II satellites, which is conditional on completing the set of GPS satellites."