India’s GPS Aided Geo Augmented Navigation system (GAGAN) will be launched here tomorrow to make it the fourth country in the world to have a satellite-based navigation system.
The system, which will be launched by Union Civil Aviation Minister Praful Patel, will provide Satellite Based Augmentation System services over India and neighboring regions, an official press release said.
It said the system would provide enhanced navigation performance for critical applications like civil aviation, marine navigation, train and road transport, precision farming, search and rescue (SAR) operations, surveying and mapping (geodetic and geodynamic), mining and so on.
According to the release, GAGAN is a Satellite Based Navigation System developed by Airports Authority of India (AAI) and Indian Space Research Organization (ISRO) to deploy and certify an operational Satellite Based Augmentation System (SBAS) for the Indian Flight Information Region (FIR), with expansion capability to neighboring FIR.
When commissioned, GAGAN is expected to provide a civil aeronautical navigation signal consistent with International Civil Aviation Organization (ICAO) Standards and Recommended Practices (SARPs) as established by the Global Navigation Satellite System Panel (GNSSP). ICAO has endorsed Global Navigation Satellite System as Future Air Navigation System (FANS) for civil aviation.
The project involves establishment of a full complement of Satellite Based Augmentation System (SBAS) consisting of 15 Indian Reference Stations (INRES), 3 Indian Navigation Land Uplink Stations (INLUS), 3 Indian Mission Control Centers (INMCC), 3 Geo-stationary Navigation payload in C and L bands and with all the associated software and communication links.
The Global Positioning System (GPS) is a satellite navigation system designed to provide instantaneous position, velocity and time information anywhere on the globe.
The baseline satellite constellation consists of 24 satellites positioned in six earth-centered orbital planes. The orbital period of a GPS satellite is one-half of a sidereal day or 11 hours 58 minutes. The orbits are nearly circular and equally spaced about the equator at a 60-degree separation with an inclination of 55 degrees relative to the equator. The orbital radius is approximately 26,600 km. With the baseline satellite constellation, users with a clear view of the sky have a minimum of four satellites in view.
The release said the current GPS constellation cannot support requirements for all phases of flight and integrity is not guaranteed. All satellites are not monitored at all times; time-to-alarm is from minutes to hours, and there is no indication of quality of service. Further, the accuracy levels are not sufficient, it said.
In the GAGAN system, the Global Navigation Satellite System (GNSS) data is received and processed at widely dispersed INRES which are strategically located to provide coverage over the required service volume. Data is forwarded to the INMCC, which process the data from multiple INRES to determine the differential corrections and residual errors for each monitored satellite and for each predetermined ionospheric grid point (IGP). Information from the INMCC is sent to the INLUS and uplinked along with the GEO navigation message to the GAGAN GEO satellite. The GAGAN GEO satellite downlinks this data to the users via two L-band ranging signal frequencies (L1 and L5), with GPS type modulation, to improve the accuracy and availability and provide integrity.