Even though interested citizens phoned the Federal Aviation Administration (FAA) reporting an unidentified flying object floating over the Arizona desert, NASA said it was just a research balloon out conducting research.

The NASA research balloon is a 4,000-pound tool used to help measure gamma ray emissions, and normally floats at 130,000 feet altitude.  Since it floats at such a high altitude and can be seen from a 170-mile distance on a clear day, people from Phoenix to Albuquerque reported seeing the balloon.

"It's something unusual," Columbia Scientific Balloon Facility researcher Bill Stepp said of the NASA weather balloon.  "People just don't know what it is."

Both the military and research institutions normally inform citizens of future research launches, especially due to a low-risk of causing panic.  There are numerous "sightings" each year by citizens who see weather balloons and military aircraft doing training runs all over the United States.  

For example, the U.S. Air Force scheduled a Minotaur 1 rocket launch over the east coast last night.  Local media informed citizens of the scheduled launch to reduce panic when people look into the sky and see a bright low light flying through the horizon.  Residents near Yuba County's Beale Air Force Base sometimes are startled as the U.S. Air Force routinely flies U-2 reconnaissance craft over the area on training runs.