Vehicles of the 31st Air Defense Artillery Brigade Patriot missile battery are ground-guided by a soldier to their next site at Otero Mesa, N.M., on April 23, 1997, during Exercise Roving Sands '97. More than 20,000 service members from all branches of the armed forces of the U.S., Canada, Germany, and the Netherlands are participating in Exercise Roving Sands '97. The exercise is designed to refine their skills in operations using an integrated air defense network of ground, missile and radar early warning systems combined with tactical fighter and bomber aircraft operating in a simulated high-threat environment. The Patriot missile battery, used for land-to-air defense, and the soldiers are deployed from Alpha Battery, 1st Regiment, 1st Battalion, Fort Bliss, Texas.