ISRO

Night flight for navigation

Print edition : July 26, 2013

The PSLV-C22 soon after it lifted off at 11.41 p.m. from Sriharikota on July 1 carrying India's first navigational satellite IRNSS-1A. Photo: S.R. Raghunathan

THE lift-off of the Polar Satellite Launch Vehicle (PSLV-C22) from Sriharikota at 11-41 p.m. on July 1 signalled the start of a special mission for the Indian Space Research Organisation (ISRO) on several counts. For the first time in its history, a satellite was launched at night. With this launch, ISRO has had 39 launches with its own rocket since 1979. The PSLV-C22 put into orbit the Indian Regional Navigational Satellite System-1A (IRNSS-1A), India’s own navigation satellite. It was put into “a special, specific orbit”, called a sub geosynchronous transfer orbit (sub-GTO), the first time this was done in an Indian launch.

The eastern sky at the Satish Dhawan Space Centre in Sriharikota lit up with a yellowish glow on the horizon when the countdown hit zero and before the rocket presented itself with flames pouring out from it. The rocket disappeared into a thick mushroom-like cloud, illuminating it with orange-yellowish flashes of light. The separation of the vehicle’s strap-on stages and the first stage was visible as never before in the interplay between light and darkness.

Twenty minutes and 17 seconds into the flight, the IRNSS-1A, weighing 1,425 kg, was injected into its precise, elliptical sub-GTO of 282.46 kilometres × 20,625.37 km. Over the coming weeks, the satellite will be moved to the geosynchronous circular orbit of 36,000 km by firing the onboard thrusters. The mission life of the satellite, built by the ISRO Satellite Centre, Bangalore, is 10 years.

ISRO Chairman K. Radhakrishnan said “a new era of space exploration has begun” with this launch. The IRNSS-1A is the first of a constellation of seven navigation satellites. The IRNSS-1B would be launched six months from now, he added.

S. Ramakrishnan, Director, Vikram Sarabhai Space Centre, Thiruvananthapuram, said the lift-off had to take place late at night because the satellite had to be put into “a special, specific orbit”. It was neither the polar orbit of remote-sensing satellites nor the geosynchronous transfer orbit of communication satellites. (It was a sub-GTO.) “The specific orbit injection timing and the equatorial-crossing time had to be factored into the lift-off time. So the launch time was optimised. Visibility from the ground station for raising the satellite’s orbit had to also be taken into account,” he said.

The need to efficiently take the IRNSS-1A to its final orbital destination was another factor behind the night launch, other ISRO scientists said. The rocket’s propulsive efficiency was also considered. India is among the select group of countries, including the United States, Russia, European countries, Japan and China, to build its own navigation satellite. The IRNSS’ services will be available only after three or four of a constellation of seven satellites are put into orbit, ISRO scientists said. These satellites will provide accurate information on the position of cars/trucks, ships and aircraft vis-a-vis their destination, with the help of a receiver. It could be an independent receiver or one that is built into a mobile phone, car, truck, ship or aircraft. Missiles, submarines, battleships and battle tanks, with the help of the receiver and the satellites in the constellation, can navigate their way towards their destination.

The IRNSS can provide precise information on the position of an aircraft with respect to the runway when the aircraft is about to land. The pilot will know how far or how high he is from the runway.

With the PSLV-C22’s success, the ISRO’s priority is its Mars Orbiter Mission, which will take place any day after October 21.

Radhakrishnan said ISRO has a busy schedule of 12 missions in this financial year (April 2013 to March 2014). They include the indigenously built INSAT-3D, an advanced meteorological satellite to be put into orbit on July 26 by Arianespace’s Ariane-V rocket from Kourou, French Guiana; the lift-off of the Geosynchronous Satellite Launch Vehicle (GSLV-D5) with the indigenous cryogenic engine, to put the communication satellite GSAT-14 into orbit in August; the launch of GSAT-7 by Ariane-V in August; the PSLV mission to put the French remote-sensing satellite SPOT-7 into orbit in December; the passive, suborbital flight of the GSLV-Mark III in January 2014 with a dummy cryogenic stage; and the launch of IRNSS-1B in March.

The lift-off of the PSLV-XL in October, with the Mars Orbiter on board, would mark the 25th mission of the PSLV since its first lift-off in September 1993.

T.S. Subramanian

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