July 2017


In A Double Feat, ISRO Successfully Launched Its Heaviest Satellite Using Its Most Powerful Rocket.

June 5, 2017 was a proud day for the Indian Space Research organisation (ISRO). It launched the locally manufactured 3,136 Kg GSAT-19 satellite, using its most powerful rocket the GSLV Mark III, on its maiden flight.


ISRO has been working since 2004 on the GSLV program. The GSLV-III is the third generation rocket developed by ISRO, after the PSLV and GSLV-II.

The Polar satellite Launch vehicle uses solid fuel and can loft satellites into Polar orbit. It has launched more than 200 small satellites including lunar probe Chandrayaan-1 & Mars orbiter Mangalyaan.

The G e o s y n c h r o n o u s Satellite Launch Vehicle, GSLV-II was developed based on rockets received from the Soviet Union, uses (cryogenic) liquid Hydrogen and liquid Oxygen as fuel. It can loft small satellites (upto 2.4 Tons) into the (much higher) Geosynchronous Tranfet Orbit (GTO). It launched the South Asian satellite recently.

The GSLV-III is ISRO's latest and most powerful, 3 stage GSLV launcher. With 4 liquid strapons which include the indigenously developed cryogenic upper stage (CUS) in the third stage, the GSLV-III can loft satellites weighing upto 4,000 Kgs into GTO. These are approximately the size of common current satellites, though large satellites today can weigh upto 6 tons each. A more powerful GSLV-III is under development for such satellites.

Incidentally, all rockets typically launch satellites weighing less than 1% of the rocket's mass! The GSLV-III is 43.4 meters tall, 4 meters in diameter and weighs 640 tons on lift off. It can deliver satellites weighing not more than 4 tons.


The GSLV-III provides India the capability to launch its own geo satellites, and enables India to offer very lucrative launch services, to other nations.

"It should take 3-4 years for us to get into the global market with GSLV-MK III, "says Ajey Lele, senior fellow in the Institute for Defence Studies and Analyses (IDSA). "Like the Polar Satellite Launch Vehicle (PSLV), until we conduct 3 to 4 successful launches in 4-6 ton class of satellites, it will not attract global customers," adds Lele.

The Satellite Weighs Only 0.5% Of The Launch Vehicle


Weighing 3,136 Kgs, the GSAT-19 has been developed and built by ISRO. Placed in geosynchronous orbit, it is described as a communications satellite.

Though its a fully functional satellite, it is primarily a development satellite used to test / verify various advanced technologies.

GSAT-19 carries Ka/Ku-band high throughput communication transponders. Besides, it carries a Geostationary Radiation Spectrometer (GRASP) payload to monitor and study the nature of charged particles and the influence of space radiation on satellites and their electronic components. GSAT-19 also features certain advanced spacecraft technologies including miniaturised heat pipe, fibre optic gyro, Micro Electro-Mechanical Systems (MEMS) accelerometer, Ku-band TTC transponder, as well an indigenous Lithium-ion Battery.


The GSAT-19's Ka/Ku Band experimental transponders are a test bed for India's large High Throughput Satellite (HTS) - the GSAT-11.

An HTS provides about 20 times more internet bandwidth via satellite than a conventional communications satellite. The ViaSat-1 and EchoStar XVII provide more than 100 Gbit/s of capacity, which is more than 100 times the capacity offered by a conventional transponder based communications satellite.

While a transponder has a single downlink frequency over a large area, a HTS has multiple, narrow beam-width links to ground, providing 6 to 7 times more data.


GSAT-19 is just a test for the GSAT-11 satellite to be launched within the next few months.

The GSAT-11 weighs a whopping 5.8 tons and will be launched using the Ariane-5 rocket from Kourou.

It will have 4 meter tall solar panels - the largest yet on an ISRO satellite. It will have 32 HTS beams providing up to 14 Gbit/s throughput for internet data.


"We are also considering GSAT-20 besides two next generation spacecraft HTS-1 and HTS-2 of very high capacity of 100 GBps each, which will cover the country's total land mass," said P.K. Gupta, Project Director for this and GSAT-11. n