What are your long term career goals?
Be honest in your answers and only give information that presents you in the best light possible. Give a clear picture of how staying in this position for a minimum of one year will be necessary for you to achieve those goals. Highlight the importance of the surveillance operator in the context of the entire team. Be enthusiastic but not overzealous: it's important to be humble as you convey the importance of the surveillance operator in relation to the rest of the team.
"In ten year's time, I'd like to be the director of loss prevention. That means that I need to know how to do a good job at each of the positions that will be reporting to me. I'm choosing to commit myself to surveillance operator at this time because I believe that surveillance plays an important part in loss prevention. After all, I can see much more than the officers can on the floor."