Why are helicopters flying low over Houston?

HOUSTON – If you see a low-flying helicopter in areas around Houston this week, there is a reason for it.

The U.S. Department of Energy’s National Nuclear Security Administration’s is conducting low-altitude chopper flights to measure naturally-occurring background radiation in support of Super Bowl LI.

WATCH: Sky 2 captures low-flying helicopters around downtown

The NNSA said the radiation assessment will cover approximately 7.5 square miles. The twin-engine Bell 412 helicopter will fly in a grid pattern over the areas at 150 feet or higher at a speed of approximately 80 miles per hour.

Flyovers will occur only during daylight hours. The NNSA said the flyovers are estimated to take about three hours to complete per area.

VIEWER VIDEO OF LOW-FLYING HELICOPTER

Flights were scheduled for Monday and Tuesday.

The NNSA said the measurement of naturally-occurring radiation to establish baseline levels is a normal part of security and emergency preparedness. The agency is making the public aware of the flights so citizens who see the low-flying aircraft are not alarmed.