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IRNSS-1G was successfully launched, completing the Indian Regional Navigational Satellite System


Images provided by: Indian Space Research Organisation (ISRO)

IRNSS-1G, the seventh and final positioning satellite in the Indian Regional Navigational Satellite System (IRNSS), was launched on a PSLV rocket at the Satish Dhawan Space Centre in India at 12:50 on April 28 local time (16:20 JST). IRNSS-1G was put on a geostationary transfer orbit, making the launch a success. In the future it will be placed on a prescribed geostationary orbit (GEO; altitude of approximately 36,000 kilometers, east longitude of 129.5 degrees) by ground control.

Completion of a positioning satellite system with three GEO satellites and four IGSO satellites

The successful launch of IRNSS-1G completed the seven-satellite IRNSS. On the GEO, one satellite each is positioned on the east longitude of 34 degrees (IRNSS-1F), 84 degrees (IRNSS-1C), and 129.5 degrees (IRNSS-1G). On the inclined geosynchronous orbit (IGSO), two satellites each are positioned with a central longitude that is an east longitude of 55 degrees (IRNSS-1A and 1B) and east longitude of 111.75 degrees (IRNSS-1D and 1E), totaling seven satellites.

The IGSO is an orbit in which the geostationary satellites have inclined orbital planes. Just like the quasi-zenith satellite orbit (QZO), the satellite nadir points draw a figure eight from north to south centered on the equator (the altitudes and inclinations differ by positioning system). For IRNSS, the altitude is 35,700 kilometers and the inclination is 29 degrees.

Satellite placement diagram at the launch of IRNSS-1E. In this way, two geostationary satellites

(IRNSS-1F [east longitude of 34 degrees] and IRNSS-1G [129.5 degrees]) were added to complete the system (the image is from the ISRO website).

IRNSS will be renamed to “NAVIC” in the future

Indian President Pranab Mukherjee praised the Indian Space Research Organisation (ISRO) for its successful launch of the final IRNSS satellite. Prime Minister Narendra Modi also congratulated the ISRO scientists and team and announced that “IRNSS” will be renamed to “Navigation Indian Constellation” (NAVIC).

NAVIC services will be offered throughout India and in neighboring countries within a 1,500-kilometer range. Several months will be spent conducting stability tests and verification tests for all seven satellites towards the service launch.