This character is responsible for obtaining information, analyzing data, reporting and making recommendations to command concerning all scientific information that is needed to acheive mission objectives. This character should have a solid background in all the physical sciences: physics, chemistry, astronomy, biology, zoology, xenobiology. The player choosing to play a science officer deosn't need to have a background in science in real life, but it is wise to research a subject in order to write technobable that is believable and interesting.
The CSO maintains a science lab station on the bridge, and also has an office in the main science lab.
An example from Star Trek would be Spock.
This is a department leadership position that is heavily featured in most missions and will see activity frequently.