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Seven satellites in 1,200 seconds. A launch similar to the one in April 2008 when ISRO launched
10 satellites.

ISRO is all set to put six nano satellites and one major ocean satellite into orbit on Wednesday from Sriharikota. The final 51-hour countdown began on Monday at 9am. Of the six nano satellites, four are from Germany, one is from Switzerland and one from Turkey. The seventh is a big one, India’s Oceansat-2 weighing 960 kg.

From the time of launch to ejection of satellites, time taken will be around 1,200 seconds. While Oceansat-2 is set to be ejected after 1,055 seconds, four nano satellites will be ejected in the next 45 seconds. Two others are meant to stay with the fourth stage of the rocket which will be on its own once the different stages of the rocket get separated.

The sequence of ejection is very similar to the April 2008 launch featuring one big satellite – Cartosat-2A and nine other nano satellites – 10 in all: once the PSLV takes off and reaches a certain height and velocity, it will first launch the Oceansat-2 and a few seconds later, the first of four nano satellites. Every 10-12 seconds, the PSLV will launch four satellites one after the other. (Two will remain with the fourth stage).

“The rocket re-orients itself everytime a satellite is to be placed in orbit. The re-orientation ensures one satellite doesn’t collide with another. The rocket effectively re-orients itself four to five times in the space of one flight,” a scientist explained.

The brain of the rocket would have made all calculations in advance – from ejection of first satellite to the fifth. The exact moment of ejection and then re-orientation for the next ejection is worked out in advance. All mathematical calculations on the ground, launch sequence and flight path have to work to zero error.

“There is no room for error. The rocket has to be in flight till the last minute which means all systems on board have to function to perfection. Once the first and second stages separate, and the fourth stage (the engines) stop, the ejection process begins until every satellite circulates in orbit,” an official said.

Oceansat-2, India’s second satellite to study oceans as well as interaction of oceans and atmosphere, is the 16th remote sensing satellite of India. It is in the shape of a cuboid with two solar panels projecting from its sides. The satellite will map fishing zones around India, measure ocean surface windspeeds as well as atmospheric temperature and humidity.

This will be PSLV’s 16th mission. From September 1993 to April 2009, PSLV has been launched 15 times. Fourteen launches have been successful continuously while only one has failed so far.

ISRO spokesperson S Satish told TOI: “It is known that PSLV has been a very successful launch vehicle. Countries realise it is a vehicle or rocket very well suited for launch of nano satellites. We were on to our 16th mission with PSLV and Germany and Swtizerland were looking for a mission. Our needs coincided and that’s how we have the six nano satellites.”

In the April 2008 launch, eight nano satellites were built by universities and research institutions in Canada and Germany.

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