Sps performance standard sps ranging signal right

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Unformatted text preview: ht-Hand Circularly Polarized 1575.42 MHz NAVIGATION UPLOAD DATA FROM CS ATOMIIC FREQUENCY STANDARD TT&C SUB-SYSTEM Helix Array Antenna FREQUENCY SYNTHESIZER AND DISTRIBUTION UNIT 10.23 MHz synthesized digital clock NAVIGATION DATA UNIT NAV & control data checks 50 Bits Per Second NAV data NAVIGATION BASEBAND 1.023 MHz clock synthesization C/A code generation Modulo-2 addition of C/A code and NAV data L-BAND SUB-SYSTEM Spread Spectrum modulation of 1575.42 MHz L-band carrier by C/A code Figure 1-1. Block IIA SPS Ranging Signal Generation and Transmission 1.4.2 The GPS Control Segment The GPS Control Segment (CS) is comprised of four major components: a Master Control Station (MCS), Backup Master Control Station (BMCS), four ground antennas, and six monitor stations. An overview of the CS is provided in Figure 1-2. The MCS is located at Schriever Air Force Base, Colorado, and is the central control node for the GPS satellite constellation. Operations are maintained 24 hours a day, seven days a week throughout each year. The MCS is responsible for all aspects of constellation command and control, to include: • Routine satellite bus and payload status monitoring. • Satellite maintenance and anomaly resolution. • Managing SPS performance in support of all performance standards. • Navigation data upload operations as required to sustain performance in accordance with accuracy performance standards. • Prompt detection and response to service failures. In the event of a prolonged MCS outage, GPS operations can be moved to a contractor-owned BMCS located at Gaithersburg, MD. When required, personnel from the MCS deploy to the BMCS within 24 hours. The BMCS is operationally exercised approximately four times per year to ensure system capability. The CS's four ground antennas provide a near real-time Telemetry, Tracking, and Commanding (TT&C) interface between the GPS satellites and the MCS. The six monitor stations provide near real-time satellite ranging measurement data to the MCS and support near-continuous monitoring of constellation performance. The current CS monitor stations provide approximately 93% global Page 3 October 2001 GPS SPS Performance Standard coverage, with all monitor stations operational, with a 5° elevation mask angle. The actual elevation angle that a monitor station acquires any given satellite varies due to several external factors. GROUND ANTENNAS TT&C Link MONITOR STATIONS SPS Ranging Signal BACKUP MASTER CONTROL STATION MASTER CONTROL STATION Commands Telemetry Navigation Uploads Ground Antenna Control Ground Antenna Status Data Traffic Management Satellite Control Function Positioning & Timing Function Command Generation Telemetry Processing Upload Generation & Control Performance Assess Function Check performance Respond if degraded performance is detected Navigation Data Ranging Measurement Data Monitor Station Control Monitor Station Status Network Control Function Ranging Measurement Processing Satellit...
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