Serge Morel        P.O. Box 17222     Sarasota, FL   34276-0222                 Fax:   (941) 378- 8008     e-mail:   serg@gte.net 9/20/2000 Page 208 of 579 UNITED STATES NAVAL OBSERVATORY (USNO) AUTOMATED DATA SERVICE (ADS) GPS SYSTEM DESCRIPTION ****************************************************************************    GLOBAL POSITIONING SYSTEM INFORMATION ===================================== The following Global Positioning System (GPS) information is obtained from the 1994 Federal Radionavigation Plan (FRP), prepared jointly by the Department of Defense (DoD) and the Department of Transportation (DoT) and other sources such as conferences, meetings and seminars.    The GPS is a DoD developed, worldwide, satellite-based radionavigation system that will be the DoD's primary radionavigation system well into the next century.  The constellation consists of 27 operational satellites. The U.S. Air Force Space Command (AFSC) formally declared the GPS satellite constellation as having met the requirement for full operational capability (FOC) as of April 27, 1995.  Requirements include:  24 operational satellites (Block II/IIA) functioning in their assigned orbits and successful testing completed for operational military functionality.   Prior to GPS FOC, an Initial Operational Capability (IOC) was declared on December 8, 1993 when 24 GPS satellites (Block I/II/IIA) were operating in their assigned orbits, available for navigation use and providing the Standard Positioning Service (SPS) levels specified below.    GPS provides two levels of service, the Standard Positioning Service and the Precise Positioning Service.    The Standard Positioning Service (SPS) is a positioning and timing service which will be available to all GPS users on a continuous, worldwide basis with no direct charge.  SPS will be provided on the GPS L1 frequency which contains a coarse acquisition (C/A) code and a navigation data message. SPS provides a predictable positioning accuracy of 100 meters (95 percent) horizontally and 156 meters (95 percent) vertically and time transfer accuracy to UTC within 340 nanoseconds (95 percent).    The Precise Positioning Service (PPS) is a highly accurate military positioning, velocity and timing service which will be available on a continuous, worldwide basis to users authorized by the U.S.  PPS will be the data transmitted on GPS L1 and L2 frequencies.  PPS was designed primarily for U.S. military use.  It will be denied to unauthorized users by the use of cryptography.    PPS will be made available to U.S. and allied military and U.S. Federal Government users.   Limited, non-Federal Government, civil use of PPS, both domestic and foreign, will be considered upon request and authorized on a case-by-case basis, provided:        * It is in the U.S. national interest to do so.     * Specific GPS security requirements can be met by the applicant.     * A reasonable alternative to the use of PPS is not available.    For questions regarding GPS policy, the user is advised to refer to the regularly appearing FRP.    The FRP is published every two years and is available from the National Technical Information Service, Springfield,VA 22161.    The latest report number is DOT-VNTSC-RSPA-95-1/DOD-4650.5 for report date 1994.