Gary Knell, president & CEO of National Public Radio since 2011, is leaving to helm the National Geographic Society in the fall.

gary knellKit Jensen, NPR chair, said Knell will remain in charge  during a transition as the network looks for a successor.

In a letter to staffers, Knell said he decided to accept the unsolicited offer to become CEO at Nat Geo after "a great deal of personal reflection.’"

Prior to NPR, Knell spent 22 years at Sesame Workshop, which included a decade as CEO.

He pushed SW's overseas expansion strategy and launched the Sprout and Noggin cable channels.

Earlier, he was managing director of Manager Media International, a multimedia company in Asia, and senior VP and general counsel at WNET/Channel 13 in New York City.

Knell, who is a trustee at Nat Geo, will succeed John Fahey as president/CEO.

Jean Case, the trustee involved in the search, said Nat Geo launched a "comprehensive and global search" for a new leader and is delighted to "announce that the perfect candidate for this crucial role was right in our own backyard."