The first all-British radar satellite is set to go into orbit on an Indian rocket, BBC reports.
Called NovaSAR, it has the ability to take pictures of the surface of the Earth in every kind of weather, day or night.
The spacecraft will assume a number of roles but its designers specifically want to see if it can help monitor suspicious shipping activity.
Lift-off from the Satish Dhawan Space Centre in Sriharikota is at 17:37 BST.
NovaSAR will be joined on its rocket by a high-resolution optical satellite - that is, an imager that sees in ordinary light.
Known as S1-4, this spacecraft will discern objects on the ground as small as 87cm across. Both it and NovaSAR were manufactured by Surrey Satellite Technology Limited of Guildford.