WASHINGTON — NASA’s plan for operating the Stratospheric Observatory for Infrared Astronomy (SOFIA) will need to be retooled if the U.S. Congress overrides a White House proposal to ground the telescope-equipped 747SP jetliner later this year, the agency’s Office of the Inspector General wrote in a report published July 9.

“SOFIA remains capable of contributing to the scientific body of knowledge and many in the science community view the observatory as a valuable resource,” the IG wrote of the $1.1 billion flying observatory, an 80-20 partnership between NASA and the German Aerospace Center, DLR. However, “NASA needs to ensure a consistent infusion of new technology, revise the methodology for calculating researcher funding, and re-evaluate the number of research hours SOFIA can fly per year,” according to the report, “SOFIA: NASA’s Stratospheric Observatory for Infrared Astronomy.”

The inspector general also said NASA might be able to reduce SOFIA science and flight operations costs if it switches to a fixed-price contract when the roughly $590 million cost-plus contract the Universities Space Research Association (USRA) has held since 2007 expires in 2016. A cost-plus-fixed-fee structure “may not be the most cost efficient contract type for the Program’s operational phase,” the IG wrote in the report.

The NASA inspector general also said the current SOFIA operations contract “does not provide mechanisms to ensure adequate NASA management and oversight of mission critical functions (such as ensuring that a civil servant direct and authorize the contractor’s work).”

John Grunsfeld, NASA’s associate administrator for science, has already agreed to review other payment structures for a follow-on science and flight operations contract. The Science Mission Directorate plans to publish its procurement strategy by June 30, 2015, according to the IG.

The Columbia, Maryland-based USRA was originally the prime contractor for the entire U.S. SOFIA development effort. However, the complexity of adapting a jetliner to carry the mission’s DLR-provided telescope drove up costs and delayed the start of science flights long enough that NASA, in 2007, took over management of USRA’s aircraft modification subcontract with L-3 Communications Integrated Systems, of Waco, Texas.

Meanwhile, the IG also said there is room for improvement when it comes to SOFIA’s technical and scientific performance.

Unlike a space-based telescope, which typically cannot be serviced once it launches, SOFIA’s 2.7-meter telescope can be outfitted with new instruments. NASA’s current plan calls for instrument upgrades every four years, but the IG, citing astronomers interviewed for the report, said an upgrade every two years would be better.

The IG also said NASA needs to increase the funding available for SOFIA science grants.

“SOFIA’s methodology for calculating research funding results in awards that are not commensurate with the complexity and uniqueness of the observatory,” the IG wrote, again citing unidentified scientists who complained that their grant awards were not large enough to properly vet data collected by SOFIA for publication in peer-reviewed journals. SOFIA was declared fully operational in May but made science observations during test flights that began in December 2010.

The IG also said NASA may not be planning to fly SOFIA often enough during its nominal 20-year mission, which will cost about $2 billion on top of the roughly $1.1 billion the agency spent to build the observatory, according to the IG.

By 2018, NASA plans to ramp SOFIA’s annual flight time up to 960 hours, putting the telescope in the air for roughly one month out of every 12. However, “[b]ased on our assessment of NASA’s assumptions, as well as discussions with SOFIA Program staff regarding actual observatory performance, it appears the Program is capable of more than 960 research flight hours per year,” the IG wrote.

The White House cited SOFIA’s $85 million-a-year operating cost when it proposed grounding the observatory as part of NASA’s 2015 budget request. DLR has said it is not interested taking over NASA’s share of the costs. When it comes to NASA science missions, only the Hubble Space Telescope is more expensive to operate than SOFIA, according to IG.

U.S. lawmakers, however, wrote the mission back into NASA’s 2015 budget as part of an appropriations process that has since stalled out, raising the possibility of a continuing resolution that would freeze spending at 2014 levels — something NASA says makes SOFIA an unsustainable proposition, given its lower priority compared with other missions.

SOFIA science operations are based at NASA’s Ames Research Center in Mountain View, California. The airborne observatory flies out of NASA’s Armstrong Research Center near Edwards Air Force Base in California.

Correction: A previous version had said the report was from the Government Accounting Office.

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.