Officials: Navigation system failure probable cause of drone crash

On the day Iran's government televised footage of a captured American stealth Sentinel drone, U.S. officials and engineers here think it was a problem with the vehicle's navigation system that probably caused it to crash.

Iranian state television on Thursday showed Iranian soldiers poking at the aircraft, tan in color with scuff marks on one wing. The unmanned aerial vehicle is one of fewer than 10 currently in operation, and its capture represents a major compromise in stealth technology. One thing the footage also showed for certain was that it was still intact and didn't self-destruct as officials had hoped.

An accompanying news story by Iran's official press agency claims Iran had hacked into the drone's navigation system and successfully brought the craft down, one of "many" allegedly downed by Iran as the U.S. intensified its campaign to spy on Iran's nuclear facilities. The CIA and Pentagon declined to comment on the matter, and while officials say there's no evidence the drone was hacked, it's not clear how they would know that.

U.S officials tell National Journal that they lost contact with the drone on Nov. 29, U.S. time, and that it was not clear initially if Iran knew it had crashed. After the link was breached and unable to be restored, the Air Force unit that flies the Sentinels immediately sent a bulletin to the National Military Command Center-a "pinnacle," designating an incident of potentially national significance.

President Obama was briefed Wednesday morning. Other U.S. intelligence assets, possibly including an imaging satellite, were diverted to the search.

Initially, the U.S. considered infiltrating a small recovery element from the Joint Special Operations Command. The Wall Street Journal reported on Wednesday that the military also planned to destroy the downed plane by missile. But both missions were foiled when Iranian troops found the scene of the crash, which has not been disclosed. Any U.S. show of force would be tantamount to a declaration of war against Iran, an escalation disproportionate to the loss.

U.S. officials are trying not to let too many details out about this supersecret drone. They won't say what type of sensor packages the RQ-170 drone, manufactured at Lockheed Martin's Skunk Works in California and tested at Area 51 and over South Korea, was carrying. One reason is that they don't wish for Iran to know precisely what each component does. In theory, the drone can be configured for high-resolution, full-motion video from high altitudes, for sampling and analyzing emissions, for tracking tagged targets on the ground, and for accurate hyper-spectral imaging of buildings and tunnels.

Its stealth comes from its color, which is relatively indistinguishable from the sky at altitudes around 50,000 feet, according to Aviation Week; its radar-refracting paint; its curves and angles, which reflect American stealth technology used since the Gulf War; and possibly for an active antiradar array located in its belly.

It's commandeered by the 30th Reconnaissance Squadron, an Air Force unit that operates out of Creech Air Force Base near Area 51 in Nevada.

But for every approved orbit, flight planners design a flight path to ensure that certain curves of the aircraft face away from the known locations of enemy radar. That helps explain why, if the drone deviated from its flight plan, Iran was able to figure out that it had gone down. The lower it glided, the more easily Iranian radar pings could "hear it."

So sensitive are the capabilities and the intelligence missions the drone is used for that the unit physically changes their data computers depending upon their customer-be it the CIA, a Defense Department intelligence agency like the National Security Agency, or other military units.

Several software packages on board are programmed to corrupt themselves if the Sentinel's communications nodes are not properly interrogated at certain points, but U.S. officials don't know which are intact and which aren't.

What worries the U.S. more than the stealth capabilities themselves is the possibility that China will help Iran access the software and figure out how to break the encryption used to protect it. Though codes can be changed, a knowledge of the underlying software logic could jeopardize other sensitive technical collection systems.

The existence of the drone was declassified last year. Its capabilities and missions remain classified at the Top Secret/Sensitive Compartmented Information level, with a Special Access Program controlling access beyond that.