Detecting if a object is behind me

Unity Engine
1

Hi,

How can I detect if a object is behing my gameobject ?
Right now, I’m doing the following :

var targetDir : vector3;
targetDir = missile_origin.transform.position - hit.point;
targetDir = targetDir.normalized;

missile origin, is the origin of my missile (in this case a ship) , and the hit.point is the contact returned by the raycast.
With this I get the direction but how do I know if the contact point is behind my ship, or in front of it ?

thanks,
Bruno

2 
function IsBehind (thisTransform : Transform, otherTransform : Transform) : boolean {
	return thisTransform.InverseTransformPoint(otherTransform.position).z > 0.0;
}

–Eric