Lieutenant Chang, a Tac Officer in 2364.
A Tac officer is a tactical specialist whose duty is to assist potential cadets in attaining the requirements needed to prepare for Starfleet Academy.
In 2364, Lieutenant Chang was serving as an Academy Tac officer at the Federation starbase on planet Relva VII. While there, he oversaw the Starfleet Academy entrance exam. (TNG: "Coming of Age")
- The term "Tac officer" is a real-life term used by today's United States Military Academy (USMA) to describe the commissioned officer assigned to oversee a company of cadets.