According to Indian Space Research Organisation (ISRO), the rocket Polar Satellite Launch Vehicle (PSLV) is being fuelled at the second launch pad at the rocket port in Sriharikota in Andhra Pradesh, around 80 km from here.
"The countdown is progressing normally," ISRO said on Tuesday.
According to ISRO the propellant filling operations are under progress.
On Wednesday at 9.26 a.m., the PSLV rocket will lift off with 20 satellites totally weighing 1,288 kg.
The rocket's main cargo will be India's 725.5 kg Cartosat-2 series satellite for earth observation.
This satellite is similar to the earlier Cartosat-2, 2A and 2B.
The other 19 satellites weighing totally around 560 kg are from US, Canada, Germany and Indonesia as well as one satellite each from Chennai's Sathyabama University and College of Engineering, Pune.
The whole mission will get over in around 26 minutes.
The images sent by Cartosat satellite will be useful for cartographic, urban, rural, coastal land use, water distribution and other applications.
According to ISRO, the 110 kg SkySat Gen2-1 belonging to Terra Bella, a Google company, is a small earth imaging satellite capable ofcapturing sub-meter resolution imagery and high definition video.
The Planet Lab's Dove Satellites are also earth imaging satellites. A total of 12 Dove satellites each weighing 4.7 kg are carried in this mission inside three QuadPack dispensers, ISRO said.
The PSLV rocket will also carry 85 kg M3MSat from Canada. The technology demonstration mission is jointly funded and managed by Defence Research and Development Canada and the Canadian Space Agency.
On the other hand, the 1.5 kg Sathyabamasat from Sathyabama University will collect data on greenhouse gases while the 1 kg Swayam satellite from College of Engineering, Pune will provide point-to-point messaging services to the HAM radio community.
Wednesday's mission will be the first time the ISRO will be launching more the 10 satellites with a single rocket.
In 2008, the ISRO had launched 10 satellites with the PSLV rocket.