KEYPORT — Keyport has an impressive collection of U.S. Navy-related Cold War artifacts and information, but one in particular captured the attention of the Central Intelligence Agency.

A secret satellite recovery mission was recently declassified, after two independent projects collaborated their sources to tell the story of one of the deepest underwater salvage operations in U.S. history. And the submersible craft that recovered American intelligence — the Trieste II (DSV-1) — has sat at Keyport’s Naval Undersea Museum for 25 years.

“We do not usually get to do things quite this big, this is a special opportunity for us,” said Mary Ryan, museum curator.

In 1971, the U.S. was in a tense conflict with the Soviet Union. Part of the U.S.’s espionage was the use of spy satellites to photograph “denied areas,” according to David Waltrop, the author of “An Underwater Ice Station Zebra – Recovering a secret spy satellite capsule from 16,400 feet below the Pacific Ocean.” Waltrop is a historian with the CIA’s Historical Collections Division, and will be giving a presentation on the mission at the museum Saturday, 1 Garrett Way, at 11 a.m.

Joining Waltrop will be key figures from the mission — Lt. Richard Taylor, one of the three pilots of the Trieste II, and Lt. Commander Beauford Myers, commander of the submersible’s support ship, the USS White Sands — as well as another researcher and former naval intelligence officer, Lee Mathers.

The KH-9 Hexagon photoreconnaissance satellite held the largest film supply at the time for U.S. intelligence — it would eject the “buckets” holding the photo film, which would be slowed by a parachute after entering the atmosphere and picked up by an Air Force aircraft, mid-air, north of the Hawaiian Islands.

In July 1971, a parachute failed for a particular bucket, and the 1,100 pound object crashed into the ocean and sank.

The CIA asked the Navy to help locate and recover the object, which sank to the ocean floor at 16,400 feet. The Navy enlisted the help of the Scripps Institute of Oceanography, which provided deep ocean transponders to locate and mark the object.

The mission kicked off in October 1971, but due to winter weather, the ships moored at Pearl Harbor until spring. The bucket was recovered in April 1972.

Myers was on previous salvage operations, but none as secret as this. The White Sands and the Trieste II had previously searched for the wreckage of the USS Scorpion, which sank in the Atlantic in 1968.

“With the exception of less than half a dozen people, no one on board the Trieste actually knew what the item was,” Myers said of the Hexagon mission. “We called it the package … We just told the sailors what we’re doing is very, very important, so don’t even think about it.”

Myers was glad to be a part of finally letting the crew members know what they did after all these years, he said.

This is one of the first times U.S. intelligence has voluntarily declassified a mission and educated the public.

About two-and-a-half years ago, Mathers was researching another mission, that was the feature in a book and documentary which postulated the Trieste II’s involvement in missile work, which he knew to be unfounded. He then came across the Hexagon satellite and it’s missing bucket — around the same time that Waltrop was researching the same mission.

“He had nothing but official documentation, I had nothing of official documentation, [so] putting the two together made for a great story,” Mathers said.

Waltrop decided to take the story on the road, and contacted the Undersea Naval Museum in January.

“For us it’s exciting to talk about what our Trieste II has done,” Ryan said. “Its cool to talk about this secret mission that it did, to give it this identity that it didn’t have before.”

This mission was the only classified dive he ever did with Trieste II, and wasn’t briefed on what exactly they would be recovering at the time, Taylor said. After he was told the mission was declassified in September 2011, he assisted Waltrop in some of his research.

Taylor was already an experienced submersible pilot, and said he never thought about the “perceived danger of what we were doing.” The Trieste II dove three times, at about 10 hours each, searching for the bucket. Each of the three pilots had about 16 cubic feet of space, he said.

“Like many things in military operations, you have long hours of complete boredom followed by intense activity,” Taylor said.

“But it was an adventure. Once you leave the surface and get down below, 400 feet or so, there’s no light, its darker than you had ever seen before,” he said. Then, “Turn on the lights and you’ll see life.” Plankton looks like a reverse snowfall as you descend, he said, and the little starfish at the bottom look like they have pipe cleaners for legs.

Without first-hand accounts and memories, Mathers said what will remain of military operations would be “cold documentation.”

“That’s not history, history is people that participated, emotions that they experienced, difficulties they overcame,” he said. “We’ll lose that if we don’t uncover these highly classified events within the lifespan of the people that participated.

“These classified programs … have remained classified for 40 years. People that have never been publicly acknowledged, people that put their life effort into these [missions] went to their grave silently.

To learn more about the Hexagon program and the Trieste II’s secret Cold War mission, see the presentation Saturday at the Undersea Naval Museum.