Sandtroopers were Imperial stormtroopers equipped with a modified armor and equipment to withstand the harsh climates of desert planets like Tatooine.
A New Hope
They where sent to Tatooine by Darth Vader to search for a escape pode with a R2 unit and a droid assistant who has the blue prints for the Death Star. While on the planet Tatooine they attacked and killed a Jawa transport, Uncle Owen and Aunt Beru. Before being mind tricked by Obi Wan Kenobi and nearly caught the Millennium Falcon.