Ariane 5. Credit: Arianespace

PARIS — Europe’s Arianespace commercial launch consortium on Nov. 14 said it had signed contracts to launch two Indian telecommunications satellites on Ariane 5 heavy-lift rockets.

Evry, France-based Arianespace said it had contracted with the Indian Space Research Organisation (ISRO) to launch the GSAT-15 and GSAT-16 satellites on separate Ariane 5 vehicles. No launch dates were given.

India has long been a regular Arianespace customer and likely will continue to be one until India’s domestic GSLV rocket is operational. GSLV is designed to launch satellites the weight of GSAT-15 and GSAT-16 — around 3,150 kilograms — into geostationary orbit.

Until the GSLV rocket is available, ISRO will remain a sought after customer for Arianespace given that most Indian-built spacecraft are light enough to occupy the lower position in the Ariane 5. Finding sufficient numbers of satellites for this position, which complements heavier satellites in the vehicle’s upper berth, has been challenging for Arianespace the past couple of years. The challenge will only intensify as Space Exploration Technologies Corp. (SpaceX) of Hawthorne, Calif., fields its new-version Falcon 9 v1.1 with an inaugural commercial launch to geostationary scheduled for Nov. 25.

ISRO said GSAT-15 will be operated at 93.5 degrees east in geostationary orbit and provide 6.8 kilowatts of power to its payload of 18 Ku-band transponders and two channels for India’s Gagan positioning, navigation and timing service, which will provide an overlay to the U.S. GPS satellites in lower-medium Earth orbit. It is designed to operate for more than 12 years.

GSAT-16, to operate at 55 degrees east, will carry 12 Ku-band, 24 C-band and 12 extended-C-band transponders. It too is designed to provide 6.8 kilowatts of power and to operate for more than 12 years.

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Peter B. de Selding was the Paris Bureau Chief for SpaceNews.