Abstract: A laser measurement system uses a high and low power laser beam to determine measurements such as rangefinding, atmospheric molecular composition and the like. A low-power laser beam is initially transmitted to detect obstructions in the path desired to be measured. The intensity of the reflected beam provides an indication of any such obstructions. Only if the path is obstruction free is the high power laser beam transmitted to effect the desired measurement. The system thus prevents harmful effects of the energy reflections from obstructions in the measuring path.