Source: Chron.com | John D. Hardin, Houston Chronicle | January 31, 2017

U.S. Immigration and Customs Enforcement Blackhawk pilot David Grantham is interviewed during a media briefing on air security for Super Bowl at Ellington Field Tuesday, Jan. 31, 2017. The air defense partners are from the Federal Aviation Administration, Customs and Border Protection, Civil Air Patrol, Oklahoma and Mississippi Air National Guard, and the Continental U.S. North American Aerospace Defense Command Region (CONR). Photo: Steve Gonzales | Houston Chronicle

U.S. Immigration and Customs Enforcement Blackhawk pilot David Grantham is interviewed during a media briefing on air security for Super Bowl at Ellington Field Tuesday, Jan. 31, 2017. The air defense partners are from the Federal Aviation Administration, Customs and Border Protection, Civil Air Patrol, Oklahoma and Mississippi Air National Guard, and the Continental U.S. North American Aerospace Defense Command Region (CONR).

The U.S. National Nuclear Security Administration, or NNSA, will test for naturally occurring radiation around the city on Tuesday using a low-flying helicopter.

The test is designed to establish a baseline for officials of Houston’s radiation levels in support of Super Bowl LI. The NNSA is a U.S. Department of Energy agency responsible for assisting national security, working to reduce the threat of weapons of mass destruction.

A twin-engine Bell 412 helicopter, operated by the Remote Sensing Laboratory Aerial Measuring System from the Nellis AFB, will be equipped with the radiation sensing technology.

According to a NNSA press release, the helicopter will fly in a grid pattern over the areas at 150 feet or higher above ground surface, at a speed of approximately 80 miles per hour. Officials from NNSA said the radiation assessment will cover approximately 7.5 square miles.

Flyovers will occur only during daylight hours, and it is estimated to take about three hours to complete per area.