JIM LEHRER:┬áTomorrow night here on PBS, “Nova” will focus on the National Security Agency’s pre-9/11 surveillance of Osama bin Laden. Here’s an excerpt.
NARRATOR: In November 1996, a known al-Qaida contact buys an Inmarsat satellite phone from a store in a New York suburb. That phone is for Osama bin Laden.
Once he starts dialing from Afghanistan, NSA’s listening posts quickly tap into his conversations. Analysts at the CIA, like Michael Scheuer, head of Alex Station, the CIA’s newly formed bin Laden tracking unit, are also eager to get the information.
NSA knew bin Laden's number
MICHAEL SCHEUER, former CIA analyst: Osama bin Laden's Inmarsat telephone was really a godsend. It gave us an idea not only of where he was in Afghanistan, but where al-Qaida as an organization was established, because there were calls to various places in the world.
NARRATOR: For NSA, tapping into satellite calls is a basic tactic in what's known as signals intelligence. Inmarsat phones transmit signals straight to the satellite orbiting over the Indian Ocean. By tracking all calls in and out of Afghanistan, the NSA quickly determines bin Laden's number: 873-682-505-331.
Once they have this, they home in on both sides of his conversations, listening to bin Laden by means of a huge dish in space and to the person he's speaking to with a dish-shaped antenna on the ground.
NSA tracks bin Laden's calls
MICHAEL SCHEUER: In the intelligence business, signals intelligence is among the most important kind of intelligence options that you have, electronic communications that are in the air, whether from telephone to telephone, from satellite to satellite, from Inmarsat radio to Inmarsat radio.
And NSA collects those with a very broad array of electronic collection capability. But once you collect them, all you have is the signals. And, ultimately, it all comes down to the human being.
NARRATOR: Human analysts plot out which numbers are being called from bin Laden's phone and how frequently. They quickly discover that most of the calls from bin Laden's phone in Afghanistan are going to a house in Yemen 2,000 miles to the south.
Yemen key to al-Qaida
JAMES BAMFORD, author, "The Spy Factory": Yemen is essential to understanding how al-Qaida operates. It's where Osama bin Laden's father was born and raised. It has a culture of clans and secrets.
It didn't surprise me that bin Laden chose his capital city, Sana'a, for his logistics and communications headquarters. What was surprising was that I found it tucked away in one of the city's poorest neighborhoods.
The headquarters was hidden in a small, undistinguished house the CIA said was the home of one of bin Laden's closest associates.
JIM LEHRER: The complete program, called "The Spy Factory," can be seen Tuesday night on most PBS stations. Please check your local listings for the exact time.