Polar Satellite Launch Vehicle, in its twenty ninth flight (PSLV-C27), launches IRNSS-1D, the fourth satellite of the Indian Regional Navigation Satellite System (IRNSS). The launch took place from the Second Launch Pad (SLP) of Satish Dhawan Space Centre (SDSC) SHAR, Sriharikota. As in the previous three launches of IRNSS satellites, PSLV-C27 used ‘XL’ version of PSLV. This is the eighth time ‘XL’ configuration is being flown, earlier seven being PSLV-C11/Chandrayaan-1, PSLV-C17/GSAT-12, PSLV-C19/RISAT-1, PSLV-C22/IRNSS-1A, PSLV-C25/Mars Orbiter Spacecraft, PSLV-C24/IRNSS-1B and PSLV-C26/IRNSS-1C missions.