are in inclined geosynchronous orbit (GSO). Two of them cross the equator at 55° E and two at 111.75° E. Ground segment The ground segment is responsible for the maintenance and operation of the IRNSS constellation. The ground segment comprises: IRNSS Spacecraft Control Facility (IRSCF) ISRO Navigation Centre (INC) IRNSS Range and Integrity Monitoring Stations (IRIMS) IRNSS Network Timing Centre (IRNWT) IRNSS CDMA Ranging Stations (IRCDR) Laser Ranging Stations IRNSS Data Communication Network (IRDCN) The IRSCF is operational at Master Control Facility (MCF), Hassan and Bhopal. The MCF uplinks navigation data and is used for tracking, telemetry and command functions. Seven FCA and two FMA of IRSCF are currently operational for LEOP and on-orbit phases of IRNSS satellites. The INC established at Byalalu performs remote operations and data collection with all the ground stations. The ISRO Navigation Centers (INC) are operational at Byalalu, Bengaluru and Lucknow. INC1 (Byalalu) and INC2 (Lucknow) together provide seamless operations with redundancy. 16 IRIMS are currently operational and are supporting IRNSS operations few more are planned in Brunei, Indonesia, Australia, Russia, France and Japan. CDMA ranging is being carried out by the four IRCDR stations on regular basis for all the IRNSS satellites. The IRNWT has been established and is providing IRNSS system time with an accuracy of (2 sigma) with respect to UTC. Laser ranging is being carried out with the support of ILRS stations around the world. Navigation software is operational at INC since 1 Aug 2013. All the navigation parameters, such as satellite ephemeris, clock corrections, integrity parameters, and secondary parameters, such as iono-delay corrections, time offsets with respect to UTC and other GNSSes, almanac, text message, and earth orientation parameters, are generated and uploaded to the spacecraft automatically. The IRDCN has established terrestrial and VSAT links between the ground stations. As of March 2021, ISRO and JAXA are performing calibration and validation experiments for NavIC ground reference station in Japan. ISRO is also under discussion with CNES for a NavIC ground reference station in France. ISRO is planning a NavIC ground station at Cocos (Keeling) Islands and is in talks with the Australian Space Agency. Signal NavIC signals will consist of a Standard Positioning Service and a Restricted Service. Both will be carried on L5 (1176.45 MHz) and S band (2492.028 MHz). The SPS signal will be modulated by a 1 MHz BPSK signal. The Restricted Service will use BOC(5,2). The