Navigation Satellites and Navigation Payload

The technology of navigation satellites develops toward the direction of relying on the ground less and less to ones where orbital data is obtained by Doppler measurements on the ground, and then ground user positions itself with the Doppler measurements. Global positioning system (GPS) has developed to a level independent of ground support for 180 days. The navigation payload is the main one related to the navigation accuracy and integrity, and also a direct device for implementing the navigation target. In particular, on‐board autonomous integrity and good on‐board response of ground integrity channel (GIC) are important development requirements gradually recognized by people; however, the current level is low with weak measures. The GLONASS navigation satellite has experienced two generational developments, and the first generation is the current GLONASS satellite in operating orbit. The second generation GLONASS‐M satellite is in the testing stage and through downlink test will replace the first‐generation network satellite.