NASA’s latest plan for the Stratospheric Observatory for Infrared Astronomy (SOFIA) appears to be heavy on flight- testing at the expense of science. One would think, based on the recently disclosed test regime, that the airborne observatory’s hardware design or flight profile had changed dramatically since NASA — under considerable pressure from Congress and SOFIA’s German partners — reversed itself and opted to continue the project earlier this year.

It is difficult to understand why NASA decided at such a late stage in the program — with work on the modified 747 aircraft essentially complete — that it now must test SOFIA for three years before beginning science operations. On top of that, astronomy during the two subsequent years will be limited to make time for still more testing. It is as if NASA suddenly awoke to the realization that the retractable door on the aircraft’s fuselage has to be open for its German-built 2.5-meter infrared telescope to collect data.

The schedule impact of the extended testing regime is clear: SOFIA will not begin making science observations until 2010, and will do so only on a limited basis until 2012, assuming all goes smoothly. This contrasts with the previous plan, under which initial science observations were to begin in 2008 after about a year and a half of flight testing.

This, in turn, will affect the scientific utilization of SOFIA. The European Space Agency’s Herschel space telescope, in which NASA has a role, is scheduled to be on orbit or approaching launch by the time SOFIA takes its first peek at the heavens. Although the two platforms will be making observations at different wavelengths, a November 2004 Independent Science Operations Review ordered by NASA concluded that the astronomy community will not have the time and resources to fully utilize SOFIA once Herschel is in operation.

Then, of course, there is the money issue. Ray Taylor, NASA’s program executive for SOFIA, acknowledged recently that the revamped test profile will significantly increase project costs. NASA already has spent some $485 million on SOFIA, with Germany having invested some $100 million. Mr. Taylor estimates that NASA will spend another $250 million to $350 million on SOFIA before completing the five years of flight-testing now planned.

Moreover, Mr. Taylor was unable to say when, or indeed whether , SOFIA will begin carrying teachers aloft on observation missions, an original program goal.

It is not unreasonable to assume that recent projections by SOFIA program officials that the observatory could be ready to conduct its first science flights by mid- 2008 at a cost of an additional $150 million were overly optimistic. But it seems just as likely that NASA now has adopted an overly conservative approach.

SOFIA’s new schedule is part of NASA’s recent decision to shift responsibility for finishing and flight testing the observatory from Ames Research Center, Moffett Field, Calif., to Dryden Flight Research Center, Edwards Air Force Base, Calif. Since Ames still has responsibility for managing SOFIA science operations — at least pending another independent review next year — the two field centers will be deeply involved in the program through at least 2012 , which is a lot of civil-servant salaries to cover.

The danger here is that Dryden, beset with declining aeronautics budgets and a greater emphasis at NASA on laboratory-based research and development, will demand more testing time than is necessary for validation purposes during the observatory’s two-year transition to full-time science operations. That would further increase the cost of the data collected by SOFIA while potentially decreasing its utilization, depending in part on whether Herschel stays on schedule.

In the meantime, by pushing SOFIA’s science return several years into the future, NASA has increased the chances that the project will be canceled, particularly in an era of badly strained resources that pits program against program and center against center.

Given the costs involved, Congress should demand a clear and convincing explanation of why NASA only recently concluded that a lengthy test period for SOFIA is necessary . Beyond that, as testing progresses lawmakers should keep a sharp eye on the program to ensure that SOFIA’s core astronomy mission is not compromised for the sake of keeping Dryden’s aeronautical engineers busy. SOFIA was devised and sold as an astronomy platform and it should stay that way.