An apparatus comprising a writer, a reader, and a sensor configured to at least sense thermal asperities of a magnetic storage medium. The apparatus includes a writer heater configured to thermally actuate the writer, a reader heater configured to thermally actuate the reader, and a sensor heater configured to thermally actuate the sensor. The thermally actuated sensor is configured to detect thermal asperities arising from the magnetic storage medium during a topographical survey of the medium. The sensor heater is configured to be rendered inoperable subsequent to the survey in response to receiving a predetermined signal while the writer and the reader heaters remain operable.