“There’s a whole lot of ways that a larger telescope might benefit you, even if it doesn’t save you money,” Hertz said.

Another option is to pair the WFIRST mission with a new initiative to view Earth-sized planets beyond the solar system, said Princeton University researcher David Spergel, who organized a workshop for scientists in September to discuss telescope proposals.

The extra-solar planet hunter also could be a stand-alone mission.

Another idea is to use one of the telescopes to study how the sun affects Earth’s magnetic field.

Like the Hubble observatory, the NRO telescopes are capable of producing extremely high-resolution images. Although they are declassified, NASA is prohibited from using the donated telescopes to produce visible-light images of Earth.

Looking beyond astrophysics missions may get at least one of the telescopes out of storage sooner.

“Astrophysics is limited in its ability to do anything based on pre-existing project developments in our budget. The rest of the agency has potentially more flexibility,” said Michael Moore, NASA’s assistant director for innovation and technology.

“Can you use the hardware to address things that are being done in advanced technology development or with humans or with robotics? That expands the universe of potential users,” he said.

NASA said responses to its request for mission proposals are due by Jan. 7.

The telescopes are being stored for NASA by ITT Exelis in Rochester, New York, at a cost of less than $100,000 a year, Hertz said.