The rovers Spirit and Opportunity have been operating on the surface of Mars since January of 2004. Interaction with these robotic vehicles involves overcoming a number of operational challenges. The challenges include the distance between Mars and Earth (the one-way travel time for commands and data can be as long as 20 minutes), environmental factors (e.g., extreme temperatures, dust storms), and the need to respond quickly and effectively to unexpected events and scientific discoveries. In the five years since the rovers landed, the Mars Exploration Rover project team has developed operational procedures for interacting with the rovers that are both scientifically productive and sustainable for what has become a long-duration mission