Senior Master Sgt. Thomas Arns, of the 527th Space Aggressor Squadron, monitors a frequency instrument while his co-worker, Capt. Brian Goodman, communicates that they are ready to test a fighter squadron's GPS capability July 20, 2016, at Nellis Air Force Base, Nev., during exercise Red Flag 16-3. The space aggressors conducted training missions to educate forces on how to identify threats and mitigate their effects. (U.S. Air Force photo/Tech. Sgt. David Salanitri)