The Global Positioning System (GPS) and other global navigation satellite systems (GNSS) have become critical elements of diverse activities including safe and efficient ground and air transportation, manufacturing, power generation, financial transactions, farming, cellular communications, first responder operations, law enforcement, consumer activities, all in addition to military operations for which they were originally designed.The widespread adoption and integration of GPS has created significant risks due to the known threats to GPS signals. With low signal power at the earth's surface, transmission in well-known and well-defined spectral bands, and sensitivity to interfering signals, GPS signals are easily jammed, spoofed, blocked, or otherwise corrupted. These risks to GPS can have tremendous economic and public health and safety impacts.This proposal takes a new approach to providing a nationally available, highly accurate, and low-cost position, navigation, and timing (PNT) system by augmenting existing commercial broadcast transmissions. Augmented Commercial Radio for Navigation (ACORN) is a general purpose PNT capability, supporting an unlimited number of simultaneous users, applicable indoors, outdoors, and airborne.ACORN should be more accurate than GPS L1 CA code, entirely independent of GPS and other GNSS, equally accurate and available indoors and outdoors, and very difficult to jam or spoof. ACORN is a significant step toward achieving assured PNT.
