WASHINGTON — Costly delays threatening the James Webb Space Telescope’s 2014 launch could limit the funding available for NASA’s next big-ticket space telescopes and a host of less-expensive projects deemed high priorities in the National Research Council’s latest 10-year plan for space- and ground-based astronomy, senior NASA officials said.

Released Aug. 13, the Astro2010 decadal survey — formally titled “New Worlds, New Horizons in Astronomy and Astrophysics” — designated the Wide-Field Infrared Survey Telescope (WFIRST) as the top priority for large missions for the decade ahead. WFIRST would be developed by NASA in partnership with the U.S. Department of Energy and launch in 2020 at an estimated cost of $1.6 billion to study dark energy, hunt for Earth-like planets and advance scientific understanding of the nature and evolution of galaxies.

Although WFIRST would be equipped with a substantially smaller mirror than the James Webb Space Telescope (JWST), the proposed telescope would have a much wider field of view, enabling it to image millions of galaxies during its envisioned five- to 10-year mission. NASA expects to review and potentially incorporate the decadal survey’s recommendations — including WFIRST and a call for increasing funding for small and medium Explorer-class missions — into its 2012 budget proposal this fall.

However, while NASA says these and other  decadal priorities could complement programs borne out of previous decadal surveys, future funding depends on the outcome of several ongoing reviews of JWST’s cost and schedule.

“Much hinges on the JWST reviews currently under way,” NASA spokesman J.D. Harrington said Aug. 17, adding that NASA’s astrophysics division chief, Jon Morse, is awaiting the outcome of several ongoing reviews of the great observatory’s test program, schedule and cost before determining future funding for new decadal priorities. “It’s a multistep process, and until he has that input, he can’t make decisions.”

Between now and its scheduled June 2014 launch, JWST is expected to consume more than a third of the $1.1 billion NASA spends annually on astrophysics. With 14 healthy space telescopes in orbit and several more in development, NASA’s budget for starting new astrophysics missions is expected to remain tight until the $5 billion JWST — NASA’s most expensive and biggest space science mission by far — clears the pad.

Morse said in July that scientists participating in the decadal survey were informed of potentially costly delays for JWST, and were asked to set new astronomy priorities accordingly.

“There aren’t a lot of resources available until we get out into mid-decade and JWST is launched, and that’s the guidance we gave the decadal survey a year ago,” Morse told a meeting of the NASA Advisory Council’s science committee here July 13, adding that the guidance he provided assumed the telescope would be delayed one year to mid-2015. Morse said he also asked the survey to consider less-dire budget scenarios should additional resources become available, but added, “I’m worried I’m not being conservative enough at this point.”

Stanford University professor Roger Blandford, chairman of the National Research Council decadal survey panel that produced the report, said the recommendations assume NASA’s astrophysics budget will remain flat or decline slightly in the decade ahead. The decadal panel also took into consideration the strain that additional JWST delays would impose on the astrophysics budget, he said.

“We did not imagine that the existing program came for free,” Blandford said.

At $1.6 billion, WFIRST is the big-ticket proposal for the decade ahead. But it is not nearly as big or as technologically ambitious as JWST or the International X-ray 

Observatory, a potentially $5 billion telescope the decadal survey recommends NASA pursue in partnership with the European and Japanese space agencies for launch sometime in the 2020s. Should NASA’s projected share exceed $2 billion, however, the mission should be scaled back, the report says. For the decade ahead, meanwhile, NASA’s investment would be limited to $200 million for technology development aimed at reducing the cost and risk of the mission.

Likewise, the Laser Interferometer Space Antenna (LISA), a $2.4 billion mission consisting of three formation-flying spacecraft, is recommended as a joint mission with the European Space Agency with the U.S. share topping $1.5 billion. But the mission’s 2025 launch target would keep NASA’s contribution around $850 million between 2012 and 2021, according to the report.

Recognizing how tight NASA’s astrophysics budget likely will be through at least 2015, Blandford said the decadal survey committee deliberately chose WFIRST — “a more modest, lower risk, cheaper mission,” in his words — as the top priority for large-scale space projects for the decade ahead. NASA’s second-highest priority, according to the report, should be spending a sustained $100 million a year on the Explorers Program to ensure a steady flow of the modestly priced astrophysics missions into orbit.

While previous decadal surveys have tended to grossly underestimate the cost and challenge of recommended missions — the 2001 survey, for example, said JWST would cost $1.5 billion — Blandford said the Astro2010 committee took great pains to assess technological readiness and costs risks, bringing in the Los Angeles-based Aerospace Corp. for independent analysis. Still, Blandford said, “there will still be surprises in the future.”