WASHINGTON – Actor Tom Cavanagh’s newest gig is taking him behind the scenes at the Smithsonian museums.

Best known as the star of television’s “Ed,” Cavanagh will host a series of 30-minute shows for the Smithsonian Institution’s joint TV unit with Showtime Networks Inc., slated to launch in April.

The new company, Smithsonian Networks LLC, announced Monday about a half-dozen of its initial 60 programs, including a co-production deal with the BBC’s flagship “Timewatch” history series and documentaries focusing on the Smithsonian’s treasured artifacts.

David Royle, executive vice president for programming and production at Smithsonian Networks, said the goal is to do more than “merely museum television” with programs that are “entertaining, informative and fun.”

No carriers have signed on, but negotiations are under way, Royle said.

Cavanagh will host the six-part series “Stories from the Vaults” from the back rooms of the world’s largest museum and research complex, which houses millions of items related to art, history, technology and science.

“One minute (Cavanagh) is coming across Phyllis Diller’s joke file, which has every joke that she’s ever told in it, and the next minute he’s taking part in a CAT scan of a Stradivarius, and then he’s in the cold tissue storage center, where they’re keeping everything from beetles to elephant blood,” Royle said.

Smithsonian Networks, which was announced last March, plans to spend at least $10 million for more than 130 hours of programming each year. Museum representatives will check the programs for accuracy and to ensure they align with Smithsonian standards.

“It’s also a good way for the public to learn a bit about the face of the museum,” said aeronautics curator Peter Jakab, who is on a committee reviewing films for the project. “They see our exhibitions, they see our objects, but they’re not necessarily clued in to all the research that goes on here.”

The programming is being offered to cable and satellite TV providers as an on-demand channel, meaning viewers who get digital channel packages would be able to watch the program of their choice whenever they want. Royle said a regular, scheduled channel in high definition is expected to launch in the fall.

The Smithsonian’s semi-exclusive deal with Showtime has raised concerns among broadcasters, filmmakers and historians whose access to museum archives and experts could be affected.

Full details of the 30-year contract, which guarantees the Smithsonian at least $500,000 a year, have not been disclosed. But it includes a clause that prohibits the Smithsonian from participating in documentaries or feature films that would compete with the Smithsonian/Showtime project. There are exceptions for news and educational programs as well as some one-time projects and those that don’t rely heavily on Smithsonian resources.

“The principle of open access is a very strong one,” said University of Maryland Professor Barbara Weinstein, president of the American Historical Association, one of several groups pressing Congress and the Smithsonian to maintain full access to the museums’ archives.

Among the projects in the works is a documentary called “The Hunt for the Double Eagle,” a mystery about the intrigue of the world’s most valuable coin, a rare American gold coin which last sold for $7 million. Of a handful in existence, the Smithsonian has two. The coins were minted in 1933 but never circulated.

“You can’t think of anything more dead than a coin. It never had life, and it doesn’t have life now,” Royle said. “And yet the story that we’re telling is a mystery story that spans three continents that has everything in it from Teddy Roosevelt, to corruption at the U.S. Mint, to a Secret Service and FBI sting at the Waldorf-Astoria.”