BEIJING — The Spanish and German governments and their industrial partners are counting on an unprecedented bilateral partnership in radar satellite surveillance to establish a firm commercial footing in a sector that has been resistant to commercial success.

The two nations’ agreement to combine their national X-band radar satellite efforts to form a single constellation, while preserving their national military requirements, has not been helped by the delays in the launch of Spain’s Paz satellite.

The 1,410-kilogram Paz, whose launch had been scheduled for 2013, is now set for a late-2014 launch aboard the Russian-Ukrainian Dnepr rocket, a converted ballistic missile that has fallen far behind in its commercial manifest.

Industry officials attending the 64th International Astronautical Congress (IAC) here Sept. 23-27 said the Aug. 22 Dnepr launch of South Korea’s Kompsat-5 radar satellite, which had been delayed by more than a year, may signal the restart of regular Dnepr flights.

Kompsat-5, which carries a synthetic aperture radar imager with a ground sampling distance as sharp as 1 meter, is only one example of the proliferation of Earth observation satellites.

The Paris-based Euroconsult consultancy in mid-September said some 136 Earth observation satellites were launched in the 10 years ending in 2012, with another 290 satellites scheduled in the coming decade.

Most of these will not be radar spacecraft. But recent developments in radar technology, including Surrey Satellite Technology Ltd.’s NovaSAR low-cost radar observation satellite, which is partly funded by the British government, indicate that, like optical sensors, radar technology is coming down in price.

Along with Canada and its Radarsat spacecraft, European nations led by Germany and Italy have pioneered the commercial use of radar imagery. Thales Alenia Space’s Italian arm built the Kompsat-5 radar sensor and is prime contractor for Italy’s civil-military-commercial Cosmo-Skymed constellation.

Astrium GmbH of Germany, with financial contributions from the German Aerospace Center, built and operates the TerraSAR-X and TanDem-X satellites, launched respectively in 2007 and 2010 on a mainly commercial mission.

Spain’s Paz will resemble TerraSAR-X and TanDem-X. The satellites’ orbits will be identical, with the spacecraft — three or, if TerraSAR-X is retired, two — spaced in orbit for maximum commercial appeal.

In a presentation here, Astrium and Hisdesat, the Spanish consortium that owns Paz, said multiple satellites in orbit will will offer more-frequent revisits for customers and facilitate certain services such as interferometry for producing 3-D terrain maps. The partnership also will provide customers with a single point of sale, with identical pricing policies, the companies said.

Astrium officials have said TerraSAR-X, launched in 2007 on a five-year mission, remains in good health and should continue operations well into 2014. If the Dnepr launch occurs in late 2014, that may give the German and Spanish companies time to demonstrate what a three-satellite constellation can do.

In the presentation, Astrium and Hisdesat said one possible in-orbit configuration is to space TanDem-X and Paz 32.7 degrees apart.

The two companies are also preparing the market for a high-resolution mode, called Staring SpotLight, that offers a ground sampling distance of 25 centimeters.

It remains unclear what the Spanish and German government policies are with respect to the commercial sale of images that sharp. France and the United States, home to the most active commercial Earth imaging companies using optical satellites, have set a resolution limit of 50 centimeters for commercial imagery sales. Images sharper than that require special government authorization.

One drawback of the Staring SpotLight mode is that it provides scenes measuring just 3.7 by 4 kilometers, as opposed to 5 by 10 kilometers for 1-meter resolution.

Astrium announced Oct. 8 that it is now offering 25-centimeter imagery to customers of TerraSAR-X and TanDem-X. Astrium is also readying the commercial introduction of its WorldDEM product line, the result of a months-long campagn flying TerraSAR-X and TanDem-X in close formation, to offer a 3-D global digital elevation model.

While the Spanish Paz satellite was entirely financed by the government, Hisdesat’s job, like Astrium’s, is to run a business with revenue generated from data sales.

“As the commercial market for data and services is limited, only a small number of satellites can capture sufficient revenues to be profitable,” Hisdesat and Astrium said in their presentation. “Partners cooperating in a constellation hence present more-robust business cases and increased return on investment.”

In its September report, Euroconsult estimated that commercial radar satellite data generated $250 million in revenue worldwide in 2012, compared to $1.5 billion for optical data that year.

The two companies said they are inviting other partners to join the constellation, either by adding additional satellites or by entering into services contracts in which a part of the constellation’s capacity is reserved.

In a Sept. 17 statement accompanying the completion of the Paz satellite’s integration in Spain, Antonio Cuadrado, head of Astrium’s Spanish division, said the staring SpotLight mode is designed “specifically for IMINT — Imagery Intelligence — and maritime monitoring applications.”

Peter B. de Selding was the Paris Bureau Chief for SpaceNews.