Secret Weapon? How Thermal Imaging Helped Catch Bomb Suspect
Authorities said a helicopter equipped with a thermal imager spotted the heat signature of a person inside a tarp-covered boat, sitting in a backyard in Watertown, Mass. Police used the sensor after an area resident reported seeing a trail of blood leading to the boat — and catching a glimpse of a blood-covered body inside. The thermal readings confirmed that there was indeed someone under the tarp, and that the person was still alive.
“Our helicopter had actually detected the subject in the boat,” Col. Timothy Alben of the Massachusetts State Police told reporters. “We have what’s called a FLIR — a forward-looking infrared device — on that helicopter. It picked up the heat signature of the individual, even though he was underneath what appeared to be the ‘shrink wrap’ or cover on the boat itself. There was movement from that point on. The helicopter was able to direct the tactical teams over to that area.”
After monitoring the body in the boat for more than an hour, police moved in and took the wounded bombing suspect, 19-year-old Dzhokhar Tsarnaev, into custody.
Thermal imagers can spot the signature of a body or other heat source inside a house, a vehicle, or in this case, a vessel. Walls may stop visible-light wavelengths, but heat can still pass through. The variations in heat emissions can be picked up by camera chips designed to be sensitive to the infrared part of the spectrum. The signature would be particularly noticeable when there’s a significant difference between the background temperature and the temperature of the heat source.