Which illumination pattern is fired perpendicular to the observer target line?

The illumination pattern that is fired perpendicular to the observer target line is the Two Gun Illumination Lateral Spread. This pattern effectively creates a spread of illumination that enhances the visibility of an area by directing light sources across a width rather than just down a depth. When illumination is needed for target acquisition or situational awareness, the lateral spread allows the observer to cover more ground and illuminate areas that may be outside of direct line of sight. This pattern is particularly beneficial in scenarios where targets are spread out or when the observer's position requires light to illuminate multiple potential threat locations simultaneously.

In contrast, the other patterns either focus on longitudinal spread or utilize multiple guns but do not specifically address the perpendicular element necessary for effective lateral illumination. Thus, the Two Gun Illumination Lateral Spread is the correct choice for this specific requirement.