The Gravity and Extreme Magnetism Small explorer, or GEMS, telescope won a NASA competition for a moderately priced space science mission in 2009 and had been scheduled for launch in 2014.

An independent review team estimated GEMS was going to exceed its $119 million budget by 20 percent to 30 percent, Paul Hertz, NASA's astrophysics division director, told reporters on a conference call on Thursday.

“"It was clear that they would not be able to complete it within their cost cap," Hertz said.

The projected cost overrun was due to technical issues in developing the telescope's instruments, which delayed the project and increased payroll costs.

The agency already has spent about $37 million on the project. It will cost about $13 million more to cancel agreements with telescope builder Orbital Sciences Corp and other contractors.

The U.S. space agency has faced massive budget overruns in some of its flagship programs, including the James Webb Space Telescope, the planned successor to the Hubble Space Telescope, that is now estimated to cost almost $9 billion.

GEMS had been designed, but not manufactured. It would have included a pair of X-ray telescopes sensitive to polarized light. It was intended to allow astronomers to study the extremely powerful magnetic fields surrounding black holes, neutron stars and other dense, high-energy objects.

A black hole is a region of space so dense with matter that not even light can escape its gravitational fist. Black holes are studied indirectly by measuring how they disrupt and affect the space around them and any nearby objects.

Neutron stars are the collapsed remains of extremely massive stars.

Although NASA has no other observatories in the works that are similar to GEMS, Hertz said some of the mission's science goals can be tackled by alternative approaches and instruments. These include NuSTAR, a high-energy X-ray telescope scheduled to launch on Wednesday.

(Editing By Tom Brown and Vicki Allen)

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