report of the action team on global navigation satellite systems (gnss)

• Four TT&C stations distributed along longitude at <strong>the</strong> Russian territory (St. Petersbourg,Moscow region, Enisseysk in Siberia, Komsomolsk in Far East);• Central system clock based on assemble <strong>of</strong> precise frequency standards; and• Signal monitoring system based on direct comparison <strong>of</strong> two-way and one-way signals.90. This architecture design ensures separate calculation <strong>of</strong> satellite orbits (ephemeris) basedon two-way tracking data by TT&C stations, and clock correction determination by <strong>the</strong> directcomparison <strong>of</strong> central clock and satellite clock time scales. This procedure has been designed tosimplify <strong>the</strong> orbit determination and time correction procedure. However, it has not ensured <strong>the</strong>progressing requirements <strong>of</strong> users. In <strong>the</strong> modernisation plan <strong>of</strong> ground segment, <strong>the</strong> technologybased on simultaneous determination <strong>of</strong> orbits and clock correction using <strong>the</strong> one-way data <strong>of</strong>spread monitoring network is foreseen.91. The user segment includes:• User receivers for different kinds <strong>of</strong> applications;• Local and regional differential subsystems;• Many managing and control systems based on combination <strong>of</strong> navigation,communication and mapping functions.92. Each GLONASS satellite transmits navigation signals in two sub-bands <strong>of</strong> L-band (L1 ∼1.6 GHz and L2 ∼ 1.2 GHz).93. GLONASS uses Frequency Division Multiple Access (FDMA) technique in both L1 andL2 sub-bands. This means that each satellite transmits navigation signal on its own carrierfrequency in <strong>the</strong> L1 and L2 sub-bands. Two GLONASS satellites may transmit navigation signalson <strong>the</strong> same carrier frequency if <strong>the</strong>y are located in antipodal slots <strong>of</strong> a single orbital plane.94. The nominal values <strong>of</strong> L1 and L2 carrier frequencies are defined by <strong>the</strong> number <strong>of</strong>satellite frequency slot from -7 to 13 shifted aside <strong>the</strong> central frequency (in L1 = 1602 MHz, inL2 = 1246 MHz) by 562.5 kHz for L1 and by 437.5 kHz for L2. In total in L1 band, GLONASSoccupies <strong>the</strong> frequency band from 1597.5 MHz to 1614 MHz and in L2 from 1241.5 to 1256.5MHz.95. GLONASS satellites such as GPS provide two types <strong>of</strong> navigation signals in <strong>the</strong> L1 andL2 sub-bands: standard accuracy signal and high accuracy signal.96. The standard accuracy signal with clock rate 0.511 MHz is designed for use by civil usersworldwide.97. The high accuracy code with clock 5.11 MHz is modulated by a special code, and itsunauthorized use (without permission <strong>of</strong> <strong>the</strong> Ministry <strong>of</strong> Defense) is not recommended.98. The standard accuracy signal is available for any users equipped with proper receiversand having visible GLONASS satellites above <strong>the</strong> horizon.99. An intentional degradation <strong>of</strong> <strong>the</strong> standard accuracy signal is not applied. The presentstandard accuracy signal provides <strong>the</strong> following accuracy performance (95%) for <strong>the</strong> user:• Horizontal:28 m22