The U.S. Department of Energy’s National Nuclear Security Administration will conduct low-altitude helicopter flights over Natick and the rest of the Boston Marathon race route Friday, April 14, through Monday, April 17, in preparation for the 127th edition of the race.

The Administration’s Nuclear Emergency Support Team (NEST) aircraft—in this case, a twin-engine Bell 412 helicopter—will measure expected background radiation as part of standard preparations to protect public health and safety on the day of an event.

The helicopter will fly in a grid pattern over the areas at 150 feet (or higher) above the ground at a speed of about 80 mph. Flyovers will occur only during daylight hours and are estimated to take approximately two hours to complete per area.

NEST is part of the Department of Energy’s National Nuclear Security Administration’s Office of Counterterrorism and Counterproliferation.