A Predator MQ-1 assigned to the 163d Reconnaissance Wing in flight over the Southern California Logistics Airport  in Victorville, Calif., in  2012. (Tech Sgt. Effrain Lopez, 4th Combat Camera, U.S. Air Force)

The situation for the Yazidi refugees atop Mount Sinjar has fluctuated in recent weeks. Airdrops have provided thousands of pounds of food and water, while U.S. assessment teams have ruled out a rescue operation because, according to U.S. officials, most of the refugees have fled the barren stretch of earth located in northern Iraq.

Yet even though the U.S. has declared the situation resolved, recent reports indicate that there are still a substantial number of displaced Yazidis on the mountain who are in need of humanitarian assistance. The number of remaining refugees has been estimated at anywhere from the low thousands to the tens of thousands, which begs the question: Why, with all of the U.S. assets around Iraq, has no one been able to provide a reasonable head count of the Yazidis? According to an officer who worked with MQ-1 Predator drone squadrons until 2010, the solution is more complicated than just throwing a handful of unmanned aerial vehicles into the sky above the Sinjar Mountains with an expectation that they would be able to see everyone below.

“It would be very difficult for one predator or even a couple to do a count,” said the officer, who asked to remain anonymous because of his prior position within his squadron. “It is very difficult for Predators to cover large swathes of territory to come up with kind of imagery.” The predators would have to be used in conjunction with different aircraft and satellites, he added, mentioning that unmanned aircraft like the Global Hawk, a larger drone that flies at high altitude, along with manned aircraft like the Joint Surveillance Target Attack Radar System (JSTARS) would be required to give an accurate assessment of the refugees on the mountain. “[Drones like the Predator] are good at finding one tank in a field, or a compound,” the officer said. “It’s almost like looking through a straw.”

Even with advanced thermal imaging carried by drones and surveillance aircraft of all types, the ability to count the Yazidis would be difficult even if they were spotted from above. “It can be hard to distinguish individuals because of infrared blending,” the officer said, referring to the way crowds of people appear on thermal imaging. “You have a ton of people packed in a small place, they’re hot, exhausted and lying down, so it’s going to be very difficult to distinguish how many there are, not to mention they move around.”

A drone policy expert who requested anonymity due to the sensitivity around his current employment said in an e-mail that while the U.S. has the ability to find out the number of Yazidis, it might not be a high priority for the overall mission. “There is no technical reason why we couldn’t get a solid ballpark estimate of the number of refugees,” he wrote. “However, there are a lot of practical reasons, like competing priorities for aerial assets … a limited supply of intelligence analysts and command attention, and perhaps even some policy reasons for rounding up on your estimate of trapped civilians, that would lead to this miscount.”

Thomas Gibbons-Neff is a staff writer and a former Marine infantryman.