If you're headed downtown to partake in Super Bowl festivities over the coming week, you might see a low-flying helicopter circling above you.

It's a good chance that helicopter is measuring "naturally occurring background radiation," a routine test performed by the federal government during large public events, according to the U.S. Department of Energy's National Nuclear Security Administration (NNSA).

A twin-engine Bell 412 helicopter is expected to take measurements around Minneapolis from Monday to Feb. 5, according to the NNSA. It is operated by the Remote Sensing Laboratory Aerial Measuring System in Joint Base Andrews, a Maryland military facility.

The helicopter will fly about 80 miles per hour in a grid pattern 300 feet above ground or higher. The tests will only be done during daylight hours and usually take about three days, according to the administration.

This baseline level of radiation in the city is then used toward security and emergency preparedness measures, according to the NNSA.

The radiation-testing helicopter will be just one of many small planes and copters buzzing the city's skies during Super Bowl week.

Many of them owe their presence to heightened security measures, others to monitoring traffic, yet others for aerial TV coverage and practice flights before the game itself.

Miguel Otárola • 612-673-4753