Although passive sensors are widely used for many mobile robotics applications that perform mapping and localization functions, there are many environments (e.g., mining and planetary) where active sensors are more practical. However, at present, most 3D SLAM algorithms that do use LiDAR and/or time-of-flight (ToF) sensors exploit only range and bearing information associated with these measurements, but not intensity information. This paper presents a new approach that attempts to explicitly incorporate an intensity model as part of a sparse bundle adjustment (SBA) estimation problem. An observability analysis shows that a solution exists, and simulation results verify its potential utility.