A droid sensorscope, also simply known as a periscope, was a device standard on R-series astromech droids, equipped with a full-spectrum transceiver with electro-photo receptors, dedicated energy receptors, heat detector, and motion detectors. Data received through the sensorscope was routed to the droid's Intellex IV internal computer. It was an extendible auxiliary visual imaging system that raised up from a panel in the droid's dome, allowing it to see what shorter droids usually couldn't.
R2-D2 used his sensorscope at various times including to navigate through a swamp on Dagobah after falling into the water shortly after the Battle of Hoth. He later used it to see after falling into the sands of Tatooine to escape Jabba the Hutt's sail barge during the Rescue of Han Solo.
R2-D2's sensor first seen rising out of the swamp in was referred to as a "periscope" in some early material surrounding the movie. The device was named a "sensorscope" with the release of Kenner's second R2-D2 action figure in 1981. The figure's packaging featured an image of the droid using a different scanner on Hoth but the toy's scanner more resembled the one seen on Dagobah. The specific scanner was later identified as a "droid sensorscope" by the Star Wars Customizable Card Game and Star Wars: Behind the Magic.