ASPEN, Colo. -- A series of unanswered questions about the downing of Malaysia Airlines Flight 17 shows the limits of U.S. intelligence gathering even when it is intensely focused, as it has been in Ukraine since Russia seized Crimea in March.
Citing satellite imagery, intercepted conversations and social media postings, U.S. intelligence officials have been able to present what they call a solid circumstantial case that the plane was brought down by a Russian-made SA-11 surface-to-air missile fired by Russian-backed separatists in Eastern Ukraine.
But they have not offered proof of what they say is their strong belief that the separatists obtained the sophisticated missile system from the Russian government. And they say they have not determined what, if any, involvement Russian operatives may have had in directing or encouraging the attack, which they believe was a mistaken attempt to hit a Ukrainian military aircraft
Moscow angrily denies any involvement in the attack; on Saturday the Russian Foreign Ministry accused the U.S. of waging "an unrelenting campaign of slander against Russia, ever more relying on open lies."
U.S. officials said they still don't know who fired the missile or whether Russian military officers were present when it happened. Determining that will take time, they said, if it's possible at all. As one put it, "this isn't '24,'" referring to the TV series that often exaggerates the speed and capabilities of the American spying machine.
On Friday, a U.S. intelligence official noted that intelligence agencies had been "heavily involved" in tracking the flow of weapons from Russian to Ukrainian separatists, and that "available intelligence points to Russia as the source of the SA-11 that downed" the jetliner. The official spoke on condition of anonymity to discuss sensitive intelligence.
Intelligence rarely meets the "beyond a reasonable doubt" standard required to convict in a U.S. court, said Michael Hayden, a former director of the CIA and the National Security Agency.
"We know what happened," he said in an interview while attending the Aspen Security Forum. "Russia is responsible for the shootdown of the jet, regardless of a few of the finer details we have yet to determine."
The Malaysian airline investigation illustrates the challenges facing the $80 billion-a-year U.S. intelligence apparatus, which is spread thin as it grapples with an increasingly unpredictable world.
In the weeks after Russian troops took over the Ukrainian region of Crimea in March, U.S. intelligence agencies ramped up collection in the area, adding satellite and eavesdropping capability, said current and former U.S. officials who spoke on condition of anonymity because they were not authorized to discuss classified information.
But spy satellites orbit the Earth and therefore don't offer persistent, hovering surveillance the way drones do. The U.S. does not appear to have captured an image of the missile being fired, officials say, although sensors detected the launch and analysts were able to determine the trajectory.
Had an imagery sensor on a low orbiting satellite captured the launch, it could have produced intelligence-rich photos of plumes of smoke and the launch vehicle, said David Deptula, a retired Air Force general and expert on intelligence systems. A company called Skybox Imaging has been able to shoot short bursts of full motion video from its satellites, so presumably the military also has that capability.
But weapons can be hidden from satellites. Although U.S. analysts said they knew that tanks and other heavy weaponry were flowing from Russia to the separatists, officials said they were unaware that the separatists possessed working SA-11 missiles, which can hit aircraft flying at high altitudes, until after the passenger jet was shot down.
Credible human sources are the holy grail of intelligence gathering, but the CIA, which has a medium-sized station in Kiev, was not in a position to recruit informants quickly among the separatists in what is essentially a war zone, officials said.
What the CIA did instead was to step up its cooperation with Ukrainian intelligence, despite concerns that the Ukrainian service is penetrated by the Russians. Key portions of the intelligence cited by U.S. officials as showing that separatists were responsible for bringing down the plane were provided by the Ukrainians, including intercepts of conversations that were verified by U.S. analysts.
Officials said social media postings available to analysts in the U.S. have also helped. The Russian ministry slammed that line of evidence gathering, contending "the Washington regime is basing its contentions on anti-Russian speculation gathered from the Internet that does not correspond to reality."
In recent days, journalists have been able to interview separatist fighters in Eastern Ukraine, some of whom acknowledged responsibility for the downing. In a report Thursday, the Italian newspaper Corriere della Sera quoted a separatist who would not give his name as saying that he was told his unit had shot down a Ukrainian military plane, only to discover the bodies of civilians.
The CIA is gathering its own first-hand reports, officials said, but they have not shared them.
U.S. officials are loathe to discuss the fruits of the National Security Agency's formidable eavesdropping capabilities, so it's not known whether the NSA picked up any conversations among Russian officials suggesting Russian complicity. Even if the agency had such evidence, officials would be unlikely to alert the Russians by revealing it publicly, one senior U.S. official said.
However, officials say, the Russian military and intelligence agencies are extremely disciplined and well aware of U.S. electronic monitoring, which makes them a tough target.
U.S. officials have not expanded in public on the case they made in a briefing to reporters Tuesday about the passenger jet.
But on Thursday, State Department spokeswoman Marie Harf said the U.S. has "new evidence that the Russians intend to deliver heavier and more powerful multiple rocket launchers to the separatist forces in Ukraine," and that "Russia is firing artillery from within Russia to attack Ukrainian military positions."
U.S. officials said the information came from satellites and other technical means, not human sources.