WASHINGTON — NASA will delay moving its newest flagship astronomy mission into its next stage of development to accommodate an independent review of the program.

NASA announced in late April that it was establishing an independent external review of the Wide Field Infrared Survey Telescope (WFIRST) to ensure that the mission, still in its early phases of development, is on track.

The WFIRST review was a recommendation of a study last year by a National Academies panel that performed a midterm review of the latest astrophysics decadal survey, released in 2010. Panelists of that study were concerned about cost growth in the mission, including an increase of $550 million from an initial estimate of $2.0–2.3 billion, and the effect it could have on the balance of NASA’s astrophysics program.

“We have to make sure that we’re learning from our experiences in the past and do not upset that balance,” said Thomas Zurbuchen, associate administrator for science at NASA, in a May 3 presentation to the National Academies’ Space Studies Board here.

The review, he said, will examine several aspects of WFIRST, including its technical requirements, cost and schedule plans, and management processes. The review will also examine whether the addition of a coronagraph — a tool that blocks light from individual stars to permit direct imaging of planets or dust disks surrounding them — is worth the potential additional cost and risk of doing so.

Zurbuchen said NASA is recruiting members for the panel over the next few weeks, and expects the study to take two months to complete. “These kind of critical reviews for our missions give us confidence that it can be implemented,” he said.

To that end, he said NASA would hold off on upcoming project reviews of the mission until the study’s report is complete and its recommendations implemented. The mission was scheduled to hold a systems requirements review in June and enter Phase B in October, according to NASA presentations about the mission from January. Zurbuchen didn’t indicate how long that might take.

WFIRST is the top-ranked large, or flagship, mission from that 2010 decadal survey. The infrared telescope will use a 2.4-meter mirror assembly provided to NASA by the National Reconnaissance Office in 2012. The mission has a “nominal” launch date of September 2025, Jeff Kruk, acting project scientist for WFIRST, said at an April 24 meeting of the Astrophysics Advisory Committee, although NASA has not committed to a formal schedule at this phase of development.

Kruk said NASA was still studying whether to make WFIRST compatible with a future starshade mission. A starshade, like a coronagraph, blocks starlight to allow for direct imaging of exoplanets. While starshades offer better performance than coronagraphs, they require the use of a separate spacecraft aligned with WFIRST, and WFIRST would require communications and navigation systems in order to work with a starshade.

“Flying a starshade is not part of the baseline mission, but we are studying what would be involved to be compatible should one be selected at a later date,” he said. Those plans will be presented at the WFIRST systems requirement review, with a decision to be made at Key Decision Point B, when WFIRST is cleared to enter Phase B of its development.

“Scientifically, I think the benefits are compelling,” Kruk said of a starshade. “I’d really like to find a way to do that.”