A little-known spy agency in Washington helped track the hour-by-hour movements of the al Qaeda courier who inadvertently led a Navy SEALs assault team directly to Osama bin Laden on Sunday, where they killed the terrorist mastermind with one shot to the chest and one to the head.

For eight months, after analysts tentatively identified a spacious walled compound near Islamabad, Pakistan, as a possible bin Laden hideout, an array of satellites and unmanned drones kept an unblinking, day-night “staring eye’’ watch, tracking individuals’ movements in and out, and following “individuals of interest’’ as they traveled across the region.

The data was continuously downloaded to an Air Force ground station housed in a nondescript hangar at Langley Air Force Base in Virginia, where teams of analysts pored over the “take’’ and streamed it live to intelligence analysis cells at the CIA, the National Security Agency and the National Counterterrorism Center.

The NCTC, housed in an innocuous office building in Rosslyn, Va., just across the Potomac River from Washington proper, operates far from the spotlight that illuminates even the secretive CIA, but it played a pivotal role in the bin Laden manhunt.

Working with the military’s Joint Special Operations Command Targeting and Analysis Center, located at Langley, and with the National Geospatial-Intelligence Agency up the river in Bethesda, Md., the NCTC analysts helped develop what the military calls a “common operating picture.’’ In layman’s terms, that amounted to a detailed four-dimensional “map’’ of the bin Laden compound and its occupants and their patterns of living and working.

The data enabled JSOC’s commandos to build, in a remote section of the U.S. air base at Bagram, Afghanistan, a full-scale replica of the al Qaeda compound at Abbottabad, an hour’s drive north of Islamabad. In constant rehearsals at the mock-up, they perfected the timing and the tactics used in Sunday’s raid.

NCTC officials declined to comment publicly on the agency’s operations or the work that led to bin Laden’s death on Sunday.

But a senior intelligence official, who briefed reporters anonymously because much of the information is classified, said the breadth and depth of the information was critical. After the compound was initially discovered last summer, he said, officials “developed good information on how life at the compound was carried out.’’

The information was so complete, he added, that “the operators who assaulted the compound felt they had all the intelligence they needed.’’ Such assessments are unusual because the military, and commandos in particular, rarely acknowledge they have “enough’’ intelligence.

In a statement, James R. Clapper, the director of national intelligence who presides over all 16 of the country’s intelligence agencies, said that in his nearly 50-year career “never have I seen a more remarkable example of focused integration, seamless collaboration and sheer professional magnificence’’ as was evident in the final hunt for bin Laden.

As impressive as it is, the elimination of the al Qaeda founder, after nearly a decade of effort, won’t have nearly the impact on global terrorism that it might have several years ago, counterterrorism officials say. Thanks to the “franchising’’ of extremist Islamist terror cells to Yemen, Somalia and elsewhere, the danger -- and the action -- has shifted away from bin Laden’s core al Qaeda group, according to NCTC director Michael Leiter.

None of the recent terrorist operations against the United States, including the 2009 Fort Hood shootings that killed 13 Americans and the drive-by shooting later that year that killed a soldier at a Little Rock, Ark., recruiting station, were directed or inspired by bin Laden. Rather, these two attacks, together with the three failed but potentially deadly attacks -- the attempted Times Square bombing, the bungled Christmas 2009 airliner bombing, and the parcel bombs hidden in printer cartridges last fall -- all were inspired or directed by a the Yemeni-based cleric, Anwar al-Awlaki, and the al Qaeda offshoot, al Qaeda in the Arabian Peninsula, also based in Yemen.

Leiter and other counterterrorism officials say that AQAP and other “franchises’’ have surpassed the original Pakistan-based al Qaeda in terms of speedy planning and imaginative attacks. They cite a further threat: the emergence of homegrown Islamist terrorists in the United States, such as the alleged Little Rock shooter, Abdulhakim Mujahid Muhammad, a 24-year-old Muslim convert formerly known as Carlos Bledsoe.

“Bin Laden personally, al Qaeda’s terrorist tradecraft, all of that is becoming less popular in most places in the world,’’ Leiter said in a December speech at the Center for Strategic and International Studies in Washington.

The affiliates, he added, “no longer simply rely upon their linkages to al Qaeda senior leadership in Pakistan but they have in fact emerged more as self-sustaining, independent movements and organizations.”

Leiter also noted that the affiliates maintain “important tentacles back to al Qaeda senior leadership” but operate with a high degree of independence.

“And, frankly, they operate at a different pace and with a different level of complexity than does al Qaeda senior leadership, and that has complicated our task significantly,’’ Leiter added.

The NCTC’s role in the killing of bin Laden is payback of sorts for the U.S. intelligence community, which was criticized for its failure to prevent the 9/11 attacks -- when a lack of coordination kept intelligence officers from fitting together known pieces of the al Qaeda plot. In the aftermath of the attacks, a presidential commission urgently recommended the establishment of a new agency to unify “strategic intelligence and operational planning against Islamic terrorists.’’

The NCTC was operational by 2004.

This time, by all accounts, the intelligence agencies and the military operational headquarters worked together smoothly and swiftly, justifying the effort put into breaking down institutional walls and separate data bases, said counterterrorism officials who requested anonymity because their operations are classified.

A former Navy pilot who flew EA6B Prowler jamming and attack planes over the Balkans and Iraq, Leiter, 42, is a cum laude graduate of Harvard Law School and clerked for Supreme Court Justice Stephen G. Breyer before starting work in counterterrorism. He was appointed as NCTC director by President George W. Bush -- and asked to stay on by President Barack Obama. He was married Saturday evening in Washington; the honeymoon was postponed.

Correction: An earlier version of this report incorrectly described bin Laden's fatal bullet wounds.