GAGAN update

Feb 2008 | Comments Off

Arjun Singh

	The user level testing of GAGAN has been completed

Ground segment of GAGAN i.e. Indian Reference Station (INRES) at Delhi, Kolkatta, Guwahati, Portblair, Ahmedabad, Banglore, Jammu and Trivanthapuram is in place. Except Portblair, other stations have been connected to Indian Master Control Center (INMCC) with fiber optic cable in synchronous loop mode. Portblair is connected through dedicated satellite communication network. Its integration and connectivity test with seven INRES with INMCC have been completed. The INRES data is being received through fiber optic cable at INMCC Banglore for corrections and validation checks of the erroneous data. Preliminary Site Acceptance Test (PSAT) of GAGAN ground element was conducted in May 2006 with help of satellite emulator.

The Ground segment of GAGAN is expected to be integrated with INMARSAT 4F1 till April 2008 and GSAT would be available for GAGAN ground segment integration by August 2008. The user level testing of GAGAN has been completed in May 2007. The Final Site Acceptance Test (FSAT) of GAGAN system was completed in August 2007. The GAGAN signal is available for testing and trial. The PRN of GAGAN GEO is 127 and continuously broadcasting correction data for users.

The installation of GPS-TEC at all 20 stations has been completed at 5° x 5° grid size. The IONO data is being collected on the basis of 24x7x365 basis for last for years and has been archived at ISRO space application center Ahmadabad. Ionospheric data from 20 TEC stations are being analyzed by a number of Indian universities and R&Dinstitutions involved in ionospheric studies for development IONO-TROPO model that is suitable for Indian airspace. As per current analysis results, 5 more TEC stations are recommended for equatorial
anomaly region which will from 2° x 2° gird size, to achieve better IONO model in the equatorial anomaly region.

The TDS phase results are to demonstrate the expected vertical and horizontal positional accuracies over 95% of the time with the associated Time-toalarm (TTA) capability. Results were better than 7.6 meters accuracies in both vertical and horizontal over 95% of the time within the perimeter of the reference stations. Using type 62 (test) messages, the TTA was better than 6.2 seconds. Results were well within the exit criteria set by ISRO and M/s Raytheon and exhibited good performance.

Flight trials are scheduled in first quarter of 2008, to check the integrity of the up linked GAGAN signals. DGCA (India) officials are involved in the training process for certification of the system and preparation of certification documents. In November-2006, FAA and AAI have signed MOC for GAGAN certification and validation of SIS.

Finally, ISRO in association with the AAI will be developing the entire system through all the stages of TDSExtended, and Final Operation Phase (FOP). The final FOP document is under review. ISRO will continue to provide technology support, maintenance and replenishment of the space segment of the system, as and when required, to maintain the system as a robust system.

Total cost of the GAGAN project is Rs 644.00 Crores (140 m USD) GAGAN Coverage is in TDS Phase on 24 Hours availability. Less coverage due to non-implementation of regional IONO-TROPO Model.