MetroStar Systems, a Reston-based information technology company, has opened an 11,500-square-foot office at the Stafford Commerce Park in North Stafford, the company announced today. MetroStar plans to service the Marine Corps at the nearby Quantico base from the office, which could be expanded. The new office is located at 51 Barrett Heights Road in a three-story, 82,000-square-foot building that the Garrett Cos. finished last year. The U.S. Navy occupies 20,000 square feet there. MetroStar plans an open house at the new office May 19.