The first all-British radar satellite will go into orbit with an Indian rocket.
Called Novasar, it has the ability to take pictures of the surface of the earth in any weather, day or night.
The spacecraft will take on a number of roles, but its designers specifically want to see if it can help monitor suspicious shipping activity.
The launch from Satish Dhawan Space Center in Sriharikota will start at 17:37.
NovaSAR will be connected on its rocket by a high-resolution optical satellite – an image sensor that sees with normal light.
Known as S1-4, this spacecraft will detect objects on the ground that are only 87 cm tall. Both it and NovaSAR were manufactured by Surrey Satellite Technology Limited of Guildford.
British engineers have long had experience with space radar, but their technology has been broader, for example for the European Space Agency. However, NovaSAR, which has the characteristic shape of a cheese grater, is uniquely British.
The radar was developed by Airbus in Portsmouth for SSTL. The mission includes low-cost, miniaturized components to demonstrate a more cost-effective approach to radar imaging.
It is used in a number of modes for applications that include oil spill detection, flooding and forestry monitoring, disaster response and plant assessment.
But perhaps its most interesting role in maritime observation.
The satellite is equipped with a receiver that can receive radio signals from the Automatic Identification System (AIS). These are the position transmissions that large ships must broadcast under international law.
Ships manipulating or deactivating these messages are often involved in smuggling or illegal fishing. If such ships appear in NovaSAR's pictures, they will be reported to the authorities.
"We are very interested in this maritime mode, which is a 400-kilometer swathing mode," said Luis Gomes, SSTL's Chief Technology Officer.
"It's important to be able to monitor large parts of the ocean – which we are not doing right now – we all saw the difficulty in monitoring this huge area with the Malaysian airline's crash in the Indian Ocean, we can do it." It's good with radar and NovaSAR, "he told BBC News.
The NovaSAR project was initiated in 2008/09 within SSTL. At that time, the idea of a radar satellite with a size of 3 mx 1 m was a breakthrough, because until then such spaceships were big, power-hungry beasts that cost a lot of money.
It is therefore somewhat regrettable that the program has been delayed because others have now succeeded in packing radar systems into small volumes. The Finnish start-up Iceye now has a suitcase-sized platform. And an American company called Capella promises a radar satellite that is not much bigger than a shoebox.
But the radar expert Martin Cohen of Airbus is not affected by these developments.
"NovaSAR is still a step change, certainly for Airbus, which you can do for a certain amount of money, but while we were waiting for a start, we did not stop there," he said. "We worked a lot on the next generation.
"NovaSAR is just the first of a family of devices that will offer different capabilities, such as finer resolutions and other parameters, and we will be transferring those capabilities to smaller spacecraft than NovaSAR."
The satellite, as it is currently configured, will operate in S-band (3.2 gigahertz), giving a best resolution of 6 meters with a stripe width of 15 to 20 km. Future variants will be among the higher frequency X-band and Sense features on the ground that are one meter in diameter and less.
The Indian Polar Satellite Launch Vehicle (PSLV) aims to bring NovaSAR and S1-4 into orbit 580 km above the Earth.
SI-4 photographs China for aviation technology of the 21st century (21AT). The Beijing-based company will use the data in the Asian nation to help with, inter alia, urban planning, crop yield generation, pollution monitoring and biodiversity assessment.