When an explosion nearly razed Iran’s long-range missile research facility in 2011 — and killed the military scientist who ran it — many Western intelligence analysts viewed it as devastating to Tehran’s technological ambitions.

Since then, there has been little indication of Iranian work on a missile that could reach significantly beyond the Middle East, and Iranian leaders have said they do not intend to build one.

So, this spring, when a team of California-based weapons researchers reviewed new Iranian state TV programs glorifying the military scientist, they expected a history lesson with, at most, new details on a long-dormant program.

Instead, they stumbled on a series of clues that led them to a startling conclusion: Shortly before his death, the scientist, Gen. Hassan Tehrani Moghaddam, oversaw the development of a secret, second facility in the remote Iranian desert that, they say, is operating to this day.

For weeks, the researchers picked through satellite photos of the facility. They found, they say, that work on the site now appears to focus on advanced rocket engines and rocket fuel, and is often conducted under cover of night. Read more.