CAPE CANAVERAL, Fla. — NASA expects to decide in May whether a technically challenging cryogenic cooler needed for one of the instruments on its flagship James Webb Space Telescope can fly with existing valves or if replacements under development as a backup will be used instead. 

“The cryo-cooler has been a problem for many years,” Eric Smith, JWST deputy program manager, told members of a NASA Advisory Council panel March 27.

“We spent a year getting valves that actually can close,” he said. 

The cryo-cooler is designed to move helium gas through 10 meters of refrigerant lines to keep the telescope’s Mid-Infrared Instrument at operational temperatures as cold as minus 269 degrees Celsius.

Initial tests showed some of the valves, built by Valve Tech Inc. of Phelps, N.Y., leaked. “They found evidence for contamination on the valves,” Smith said.

New valves were installed, but more testing is planned to assure the problem will not recur. Meanwhile, a second company, Springfield, N.J.-based Valcor Engineering Corp., has manufactured an alternative set of valves, which also is undergoing testing. 

“The decision in May would be ‘Do we keep the ones that are in there currently, or do we swap them out for [these] new Valcor valves,’” Smith said. 

JWST, the $8.8 billion successor to the Hubble Space Telescope, remains on track for launch in October 2018. 

“We’re in very good shape as far as the amount of schedule reserve that we have,” Smith said. 

That may change as the telescope’s science hardware undergoes a key series of cryogenic vacuum tests. The first three-month run begins this summer. 

“Things are going well, but I don’t think anyone should breathe too easy because there’s a lot … of work that has to get done,” Smith said.