Final answer:
The observer uses called-for-fire procedures for certain missions, and Time-on-target information is communicated to the Fire Direction Center for coordinating the engagement time of a target.
Step-by-step explanation:
The observer normally uses called-for-fire procedures for suppression and smoke missions. Time-on-target will tell the Fire Direction Center (FDC) the total time to engage a target. The concept of Time-on-target is pivotal in military operations where multiple weapons systems coordinate their fire to strike a target simultaneously, thus maximizing the effect and minimizing the chance for the target to take cover or retaliate.