LONDON — The British government on Nov. 29 announced that it will finance about half the cost of building and launching a radar Earth observation satellite to be built by small-satellite specialist Surrey Satellite Technology Ltd. (SSTL) at a head-turning cost even by SSTL standards.

The investment, totaling 21 million British pounds ($32.7 million), will be matched by SSTL and its corporate parent, Astrium Satellites, to launch a 300-kilogram satellite designed to prove the technology to future investors.

Sir Martin Sweeting, SSTL’s chairman, said the spacecraft, which will be the first of SSTL’s NovaSAR products, will be built and launched for a total cost of around 45 million pounds.

In a Nov. 29 interview, Sweeting said a four-satellite constellation could be placed in orbit for around 200 million pounds.

The NovaSAR platform, designed by Guildford-based SSTL, will be equipped with an Astrium payload to provide maritime surveillance and coastal monitoring with a radar imager that has a ground-sampling distance of between 6 and 30 meters.

The 6-meter imagery will be provided with a swath width of 12 to 20 kilometers. The 30-meter-resolution products, including maritime surveillance services, will have a swath width of 750 kilometers.

The NovaSAR platform is designed to operate for seven years in an orbit of around 580 kilometers. Its principal instrument will be a phased array radar antenna measuring 3 meters long and 1 meter wide.

The British government’s decision to invest in the NovaSAR platform was announced by British Universities and Science Minister David Willetts. The funds will be made available through the U.K. Space Agency.

U.K. Space Agency Chief Executive David Williams said the government’s decision, coming at a time of sharp reductions in public spending, illustrates the faith government officials have in SSTL’s ability to deliver on its promise.

In a Nov. 29 interview, Williams said the government’s investment a decade ago, through a program called Mosaic, in SSTL’s optical satellite product line paid handsome returns and paved the way for the SSTL-coordinated Disaster Monitoring Constellation of optical Earth observation satellites.

There are six Disaster Monitoring Constellation satellites in orbit, and SSTL is at work on three more satellites whose construction and launch already has been fully paid by a Chinese customer under a contract valued at 110 million pounds.

SSTL has performed airborne trials to simulate the performance of its NovaSAR platform, and these results gave the British government sufficient proof that the investment was worthwhile, Williams said.

Also motivating the government was its belief that the SSTL-Astrium radar satellite design represents a revolution in the cost of radar satellite systems that could stimulate a global market for radar data. Securing a leading market position for British industry is one of the goals of the U.K. Space Agency and of this investment, Williams said.

“People still don’t really understand how to use radar data; it’s more difficult than optical,” Williams said. “But if you can get the costs down you can attract a market. There is some risk, but we think this is where targeted government investment can be valuable.”

Israel Aerospace Industries has designed a similarly lightweight radar satellite platform called TecSAR, with one sensor sold to the Indian government. But neither TecSAR nor competing platforms built for German and Italian government and commercial applications have achieved as much success in the market as their backers had hoped.

Sweeting said a radical reduction in the cost of the system should change that. “We have heard a very strong interest expressed by potential customers in a system such as this,” Sweeting said of the NovaSAR design. “What we think we can do is similar to what we have done with the Disaster Monitoring Constellation. Everything changes when you get the costs down.”

Sweeting said that assuming work on the demonstration satellite begins in early 2012, the first satellite could be ready for launch by late 2013 or early 2014.

He said a logical extension of the mission would be to include an Automatic Identification System terminal to identify ships by their ownership, cargo and destination using shipborne transmitters already required by maritime regulations. Whether this will be added, he said, is unclear.

SSTL keeps regular contact with the launch services sector to determine where prices are going, and Sweeting said launch costs for small satellites are increasing. But he remains convinced that for 200 million British pounds a four-satellite constellation could be built and launched.

Peter B. de Selding was the Paris bureau chief for SpaceNews.