The 33-hour countdown for the launch of two earth observation satellites on-board Polar Satellite Launch Vehicle-C42 from the space port of Sriharikota, about 110 kilometers from in Chennai, began at 1.08 pm on Saturday.

The Indian Space Research Organisation's trusted workhorse Polar Satellite Launch Vehicle-C42 would carry the satellites, NovaSAR and S1-4, together weighing over 800 kilograms, at lift off on Sunday at 10.07 pm, ISRO said in a release.

The foreign satellites, meant for forest mapping and flood and disaster monitoring, among other uses, would be released into sun synchronous orbit at a height of 583 km, it added.

They have been developed by Surrey Satellite Technologies Limited, United Kingdom.

The mission is a commercial arrangement between the company and Antrix Corporation Limited, which is the commercial wing of ISRO.

This would be the 44th flight of the PSLV and the third launch by ISRO this year.

In January, PSLV-C40 launched India's weather observation satellite Cartosat 2 Series and PSLV-C41 launched IRNSS - 1I navigation satellite in April.

Photograph: Kind courtesy ISRO