ndia's Polar Satellite Launch Vehicle has successfully launched the second satellite of the Indian Regional Navigation Satellite System on 4 th april 2014. Blasting off from the Satish Dhawan Space Center on India's east coast at 11:44 UTC, the PSLV rocket performed a 19.5-minute flight before releasing the satellite into its intended Geosynchronous Transfer Orbit.
The IRNSS constellation of satellites is currently under construction and will consist of seven spacecraft in Geostationary and Geosynchronous Orbits when complete. Once operational, IRNSS will give India independent access to navigation data without relying on foreign programs like GPS or Glonass. Friday's launch was preceded by a 58-hour and 30-minute countdown operation that commenced on Wednesday at 1:14 UTC and prepared the PSLV for liftoff. To loft IRNSS-1B, the PSLV used its largest configuration known as PSLV XL. The first two days of the long Countdown Operation were dedicated to fueling the second stage and fourth stage of the launcher as well as the Roll Control Thrusters on the first stage. PSLV uses a combination of solid- and liquid-fueled stages – the boosters, PS1 first stage and PS3 third stage use solid propellants that are loaded ahead of launch vehicle integration. Overall, PSLV stands 44.5 meters tall, has a diameter of 2.8 meters and a liftoff mass of 320,000 Kilograms. On Friday, the Mobile Service Tower was retracted, first to a stand-off distance of 50 meters before rolling to its launch position, 160 meters from the rocket that was fully fueled at this point. Afterwards, teams made final close-outs on PSLV and the service structure before departing the launch complex . | 
Photo: Indian Space Research Organization
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Throughout the countdown, teams were watching over all systems of the rocket and the payload and completed electrical tests, checkouts of the communications system, control system verifications and Flight Termination System testing. Flight computers were configured for the Terminal Countdown Sequence and the final systems check was performed less than one hour from launch. When all systems were verified in good condition, the formal authorization for launch was given and the countdown headed into its Terminal Sequence at T-8 minutes.
At that point, the IRNSS-1B spacecraft underwent its transition to flight mode and it was switched to internal power. At T-5 minutes, the flight computers of PSLV were configured for flight and received their appropriate flight software. Ground tracking station readiness was verified to ensure PSLV could be tracked on its way downrange. At T-3 minutes, the launch vehicle transitioned to flight mode. Final countdown procedures included the pressurization of the propellant tanks aboard the launch vehicle that also transferred to internal power. At T-1 minute, the on-board Master Sequencer assumed control of the countdown, putting the rocket through the final steps ahead of liftoff.
At T-3 seconds, the two Roll Control Thrusters on the first stage ignited. As clocks hit zero, the PS1 Core Stage received its ignition command. To provide an extra kick to the vehicle, four of the six Solid Rocket Boosters were ignited in pairs at T+0.5 and T+0.7 seconds.
At that point, the IRNSS-1B spacecraft underwent its transition to flight mode and it was switched to internal power. At T-5 minutes, the flight computers of PSLV were configured for flight and received their appropriate flight software. Ground tracking station readiness was verified to ensure PSLV could be tracked on its way downrange. At T-3 minutes, the launch vehicle transitioned to flight mode. Final countdown procedures included the pressurization of the propellant tanks aboard the launch vehicle that also transferred to internal power. At T-1 minute, the on-board Master Sequencer assumed control of the countdown, putting the rocket through the final steps ahead of liftoff.
At T-3 seconds, the two Roll Control Thrusters on the first stage ignited. As clocks hit zero, the PS1 Core Stage received its ignition command. To provide an extra kick to the vehicle, four of the six Solid Rocket Boosters were ignited in pairs at T+0.5 and T+0.7 seconds.
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