Sensor echo
A sensor echo was a type of echo which appeared on sensors.

In 2366, Acting Ensign Wesley Crusher picked up an unusual echo on the navigational sensors. Lieutenant Worf reported that something which did not fully register on the 's instruments was tracking the ship, as well as matching their speed and heading. Since there was no known natural phenomenon capable of travel at warp velocity, Lieutenant Commander Data suggested that it was either a sensor malfunction or another ship was covertly following them. Data ordered Worf to continue monitoring the precise position of the echo, and to initiate yellow alert if there was any sudden change in behavior. Geordi La Forge later detected another echo on the port sensor array. ()

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