Government authorities responsible for Britain’s space budget have defended their spending on space science missions as generally within budget and scientifically worthwhile, but agreed they may have overestimated the financial returns to British industry from Europe’s Galileo satellite-navigation system.

Responding to a critique of space spending issued by Britain’s Public Accounts Office (PAO) earlier this year, the agencies that contribute the lion’s share of the budget of the British National Space Centre (BNSC) rejected the allegation that space projects are routinely expensive, risky and over budget.

According to the response, delivered collectively in a document dated October 2005, Europe has launched 14 space-science missions since 1985, with only one loss — the four Cluster satellites destroyed in an Ariane 5 launch failure in June 1996. But the Cluster mission was rebuilt and successfully launched. Almost all of Britain’s space spending is invested through the 17-nation European Space Agency.

The response from the BNSC partners says “the average cost at completion of these [14] missions has been 4 percent above the cost agreed to … at the outset. All have been scientific successes.”

The response accepts the PAO concern that the BNSC partners’ earlier assertions about Galileo — that Britain’s investment of 78 million pounds ($137.8 million) would be worth 6 billion pounds ultimately — may be exaggerated.

The BNSC partners, in particular the Department of Trade and Industry, have asked the European Commission to update estimates on Galileo’s likely economic benefits with an independent assessment expected to be completed late this year.

A British parliamentary committee also questioned estimates of Galileo’s economic benefits, saying much of the increased economic activity ascribed to Galileo would occur anyway as a result of a less-expensive system now being implemented to enhance the signal reliability and accuracy of the existing U.S. GPS network. This GPS enhancement, similar to work done in the United States and Japan, uses small payloads on a few geostationary-orbiting communications satellites to verify and enhance GPS performance.

The response also says the Natural Environment Research Council, another agency that helps finance BNSC, has established a “risk register” to monitor risks associated with Earth observation missions. Among the risks currently appearing on the register is “a risk for the failure to operate the High Resolution Dynamics Limb Sounder instrument,” which is flying on NASA’s Aura satellite. “[M]echanisms are in place to address this risk,” the council says.

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