BY ORDER OF THE SECRETARY OF THE AIR FORCE AIR FORCE ...

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AFMAN 11-217V1 3 JANUARY 2005
6.12.2.3. User Segment (User Equipment - UE). The GPS user segment consists of a
variety of configurations and integration architectures that include an antenna and
receiver-processor to receive and compute navigation solutions to provide
positioning, velocity, and precise timing to the user.
6.12.3. Signal Characteristics. Each satellite transmits three separate spectrum signals on
two L-band frequencies, L1 (1575.42 MHz) and L2 (1227.6 MHz). L1 carries the P (Y)
code and C/A code; L2 carries only the P (Y) code. The P (Y) code is normally
encrypted and is also known as PPS, while C/A code is unencrypted and is known as the
SPS. Only authorized users with cryptographic equipment and keys and specially
equipped receivers may use PPS. The navigation data contained in the GPS signal are
composed of satellite clock and ephemeris data for the transmitting satellite plus GPS
constellation almanac data, GPS to UTC time offset information, and ionospheric
propagation delay correction parameters for single frequency users. The entire
navigation message repeats every 12.5 minutes. Within this 12.5 minutes, satellite clock
and ephemeris data are sent 25 separate times so they repeat every 30 seconds.
Figure 6.8. GPS.
6.12.4. Integrated Systems. Although GPS is designed to replace some navigation
equipment, the way it is integrated into the navigation system will depend on the mission