HOUSTON (KTRK) -- It's a scary sight: a helicopter making circles at extremely low altitudes.
Recorded on cellphone video, the chopper could be seen flying between buildings only a few hundred feet off the ground.
Eagle-eyed office-goer Henri Dubiton posted the video to Youtube showing the chopper. The helicopter is registered to the Department of Energy's National Nuclear Security Administration.
The NNSA confirms its choppers routinely conduct "aerial radiation monitoring" at areas of high profile events. In the last year, it flew similar missions around the Democratic and Republican National Convention.
"The measurement of naturally occurring radiation to establish baseline levels is a normal part of security and emergency preparedness," a news release said.
ABC13 has also learned that the helicopter is taking radiological readings near NRG Stadium as part of the Super Bowl's emergency preparedness plan. The chopper is gathering data as a baseline to be able to respond to any radiological emergency that might happen before, during or after the game.