Scanning range
The scanning range, or scanner range, was the range by which a scanner could detect someone or something.

In 2268, after leaving the  at high warp speed, the dikironium cloud creature quickly traveled out of the scanner range of the starship. () 

In 3189, the  landed in the Saturnian system, which lay outside the scanning range of Earth. ()

See also 
 Sensor range

Measurements