Obi-Wan "Ben" Kenobi is a fictional character in the Star Wars franchise. Within the original trilogy he is portrayed by Alec Guinness, while in the prequel trilogy a younger version of the character is portrayed by Ewan McGregor. In the original trilogy, he is a mentor to Luke Skywalker, to whom he introduces the ways of the Jedi. In the prequel trilogy, he is a master and friend to Anakin Skywalker.

Obi-Wan Kenobi is introduced in the original Star Wars living as the hermit Ben Kenobi on the planet Tatooine. When Luke Skywalker and the droid C-3PO wander off in search of the lost droid R2-D2, Obi-Wan rescues them from a band of native Tusken Raiders. At Obi-Wan's home, R2-D2 plays a recording of Princess Leia saying that R2-D2 contains the plans for the Death Star, the Galactic Empire's superweapon. Leia asks him to deliver the droid and the plans safely to the planet Alderaan in order to help the Rebel Alliance. Obi-Wan reveals his true identity and explains that he is a Jedi Master, a member of an ancient group of warriors that were hunted down and exterminated by his apprentice Darth Vader, the apparent killer of Luke's father. He gives Luke his father's lightsaber and asks him to accompany him to Alderaan and take up Jedi training. Luke declines, but after finding that his uncle Owen and aunt Beru have been killed by Imperial troops, he agrees to go with Obi-Wan to Alderaan and to train as a Jedi.  In the spaceport city Mos Eisley, Obi-Wan uses the Force to trick Imperial troops into letting them through a military checkpoint. They enter a local cantina and make a deal with two smugglers, Han Solo and Chewbacca, to fly them to Alderaan aboard their ship, the Millennium Falcon. During the journey, Obi-Wan begins instructing Luke in lightsaber combat. He suddenly becomes weak and tells Luke of "a great disturbance in the Force". Emerging from hyperspace, the party finds that Alderaan has been destroyed by the Empire, and the Falcon is attacked by an Imperial TIE Fighter. The trio chases the TIE fighter to the Death Star, and subsequently get caught in the space station's tractor beam. On board the Death Star, Obi-Wan shuts down the tractor beam, but Darth Vader confronts him and they engage in a lightsaber duel. Obi-Wan uses the duel to distract Vader as Luke, Leia, Han and Chewbacca escape to the Falcon. Although Vader strikes Obi-Wan down, his body mysteriously vanishes the moment he dies. At the climax of the film during the Rebel attack on the Death Star, Obi-Wan speaks to Luke through the Force to help him destroy the Imperial station.  In The Empire Strikes Back, Obi-Wan Kenobi appears several times as a spirit through the Force. On the planet Hoth, he appears to instruct Luke to go to the planet Dagobah to find the exiled Jedi Master Yoda. Despite Yoda's skepticism, Obi-Wan convinces his old master to continue Luke's training. He appears later to beseech Luke not to leave Dagobah to try to rescue his friends on Cloud City, although Luke ignores this advice.  In Return of the Jedi, Obi-Wan again appears to Luke after Yoda's death on Dagobah. Obi-Wan acknowledges that Darth Vader is indeed Luke's father, revealed by Vader himself in the previous film and confirmed by Yoda on his deathbed, and also reveals that Leia is Luke's twin sister. After the Rebels destroy the second Death Star and defeat the Empire, Obi-Wan appears at the celebration on Endor, alongside the spirits of Yoda and the redeemed Anakin Skywalker (Vader's former Jedi self).

Using a quote from the above article, answer the following question: What is his role on the planet?
deliver the droid and the plans safely to the planet Alderaan in order to help the Rebel Alliance.