an array of triboelectric sensors is used for testing the electrostatic properties of a remote environment . the sensors may be mounted in the heel of a robot arm scoop . to determine the triboelectric properties of a planet surface , the robot arm scoop may be rubbed on the soil of the planet and the triboelectrically developed charge measured . by having an array of sensors , different insulating materials may be measured simultaneously . the insulating materials may be selected so their triboelectric properties cover a desired range . by mounting the sensor on a robot arm scoop , the measurements can be obtained during an unmanned mission .