The 51 hour countdown for PSLV-C21, the 100th satellite launch of ISRO, began at 6.51 this morning. ISRO spokesperson Deviprasad told AIR that during the count-down, propellant filling operations of the liquid propellant second stage and fourth stage of the launch vehicle will be carried out alongwith mandatory checks.

The satellite launch mission, which met on Wednesday at Satish Dhawan Space Centre, Sriharikota, has cleared the launch of PSLV-C21 piggy backing SPOT-6 and PROITERES mission at 9:51 hours, on Sunday.

The charging of batteries and pressurisation of propellant tanks onboard the satellite, will be performed during the process of the countdown. Readiness of various ground systems such as tracking radar systems and communication networks will also be ascertained.