"The 49 hour countdown of PSLV C23 Mission started at 08:52 AM at Satish Dhawan Space Centre at Sriharikota," ISRO said.
The Launch Authorisation Board (LAB), which met yesterday at Sriharikota, cleared the launch, paving the way for the start of the countdown.
The launch, originally fixed at 9.49 AM on June 30, has been rescheduled for 9.52 AM due to the probability of space debris movement during the launch window.
Prime Minister Narendra Modi is set to witness the launch of the French satellite, SPOT-7 and the co-passenger spacecraft from Canada, Germany and Singapore from the first launch pad at Satish Dhawan Space Centre at Sriharikota, about 100 km from here.
SPOT-7 is an Earth observing satellite, similar to Indian Remote Sensing System (IRSS).
ISRO has so far launched 35 satellites of foreign countries onboard its workhorse Polar Satellite Launch Vehicle (PSLV).