PARIS — A comprehensive outside review of Europe’s space science program is urging managers to adopt a harder line with the scientists who dream up missions, the teams that oversee satellite budgets and the European Space Agency (ESA) departments that act as contractors for science missions.

The first critical assessment of ESA’s science program in 15 years also is urging ESA to further open itself to space science collaboration with the United States, China, Russia, India and Japan.

The Science Program Review Team (SPRT), which ESA hired in February 2006 to take a gloves-off look at the way space science is conducted in Europe, says space scientists must accept the fact of reduced European government support.

ESA’s space science budget is funded by mandatory contributions from the agency’s 17 member stages based on each nation’s gross domestic product. ESA officials have long said the mandatory aspect of the science budget has given the program a necessary stability and predictability. But ESA’s space science budget, which currently is about 400 million euros ($534 million) per year, has dropped by 20 percent in inflation-adjusted terms since the mid 1990s.

The SPRT, which completed its work in March and has submitted its final report to ESA’s ruling council for review, assumes space science spending in Europe will remain flat even if ESA ultimately is merged into the 27-nation European Union’s executive arm, the European Commission.

Europe’s space science program has not accepted these financial realities and must do so now to avoid a financial crisis, the SPRT says in its 66-page report.

Led by Reinder van Duinen, former president of the European Science Foundation, the SPRT recommends measures to make the best of this situation. The report says the SPRT purposely avoided making any recommendations that would be rejected as politically unacceptable or unrealistic.

One of the most specific proposals — that ESA find an immediate 200 million euros in savings before accepting new missions for the period 2015-2025 — has been accepted by ESA Science Director David Southwood and the Science Program Committee, which sets science priorities based on ESA’s budget limits.

Southwood said in an interview that he is comfortable with virtually all of the other report’s recommendations as well.

Even so, the SPRT is proposing that ESA’s science directorate cast a sterner eye on most of its partners in Europe, and that it swallow its pride and seek more-regular bilateral and multilateral missions with the major space powers outside Europe.

Here are some of the main proposals made by the SPRT:

Technology validation. As science satellites become more sophisticated, program managers can no longer afford to take the word of a science institute as to the technical feasibility of a given payload instrument and proposed financial budget.

To prevent an under-evaluation of payload costs, the SPRT proposes that an outside evaluation of new payload proposals be made before a satellite mission is accepted to assure that the work can be done on time and within budget.

Further, the SPRT says, ESA’s science budget should set aside 5 percent as a contingency against surprises in payload development.

   Budget firmness. Any mission with a cost overrun of more than 20 percent should be frozen immediately, and then de-scoped to reduce its costs or canceled to make room for another program. To assure that science managers are warned of the budget problems as early as possible, science managers need cost-at-completion estimates that include industry input from the beginning.

   Payload oversight. The SPRT says Europe should not abandon its current practice in which national science institutes, and national budgets, build ESA science payloads, with ESA responsible for integrating the payloads and then testing and launching the satellites.

But ESA and the Science Program Committee should insist on binding commitments from these national institutes as to cost and schedule and assure that there are no conflicts of interest between those evaluating and those being evaluated. Faced with payloads whose budget increases threatened their cancellation, ESA in the past has stepped in to provide unforeseen funding, a practice the SPRT says should be used only rarely, and as a last resort.

   Mission support costs. In one of its most striking findings, the SPRT says that in the 1990s, ESA’s science directorate used to spend 75 percent of its budget on developing satellites and launching them, with the remaining 25 percent spent on contracts with other ESA centers for satellite testing, mission management and other support services.

For reasons the SPRT does not explain, these support services began growing in the late 1990s and now consume fully 50 percent of the agency’s science budget.

The formula used to determine how much different ESA directorates bill others for services is complicated, and the subject is a delicate one at the agency.

Nonetheless, the SPRT says ESA should set a firm ceiling of 40 percent of its budget to be spent on these services. “A critical evaluation and assessment, with benchmarking, of the structure, performance and costs of the various centers and support activities under the ESA umbrella must be undertaken, the results reported,” the report says.

   Mission extensions. The success of ESA’s science satellites in recent years has led to a natural increase in the budget for extending missions beyond their planned expiration dates. The SPRT says ESA is now spending 60 million euros a year on missions that, in their original program definitions, were supposed to have ended.

Pulling the plug on a healthy science satellite will never be easy, the SPRT says. But an effort must be made to reduce the weight of mission extensions on the science budget, and mission extension should be included in the program budget from the start, the report says.