27.9.16

PSLV puts 8 satellites into orbit


With its engine turned off for much of the mission duration that lasted for two hours and 15 minutes, the PSLV glided its way not just across the earth, but the annals of India's spacefaring history , placing eight satellites in multiple orbits along the way on Monday .
The rocket had two coasting periods, which together lasted for more than 1.5 hours after its engine was reignited and shut down twice to help manoeuvre the rocket to inject the satellites into their orbits.About 17 minutes after PSLV-C35 lifted off from the first launch pad at Satish Dhawan Space Centre, Sriharikota, Scatsat-1, India's weather monitoring satellite, was injected into a polar sun synchronous orbit. About 100 minutes later, seven other satellites were placed in the other polar orbit.
When PSLV-C35 placed Scatsat-1in the polar synchronous orbit 17 minutes after lift-off from Sriharikota, both the satellite and the rocket began to circle the earth. About 66 minutes later, the rocket's fourth-stage engine was reignited and shut down for about 20 seconds, as a preparation to switching orbits and launching the rest of the satellites. The shutdown gave the necessary thrust for the rocket to manoeuvre further and change orbits The rocket was coasting at a speed of about 27,000 km per hour.
The engine was restarted and cut off for 20 seconds, about 45 minutes after it coasted for the second time during its mission. A minute later, seven other satellites were placed in orbit one after the other within 3.45 minutes. “PSLV launches usually last 20 to 25 minutes. But this launch lasted nearly two-and-a half hours. It was almost like having two separate launches,“ said B Jayakumar, mission director.
Very few space-faring countries have achieved this feat. European Space Agency's Vega rocket recently accomplished a twin-orbit manoeuvre.
While Isro tested the restart and shutdown of its fourth-stage engine in two previous PSLV launches, the launch on Monday was still complex at various levels. “One side of the rocket was getting hot, as it was facing the sun while the other side was using heat to move,“ Jayakumar said. He added that PSLV now has the flexibility to suit customers' demands.

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