Dobson was a scientist at Space Control and Dr Bruno Taltalian's chief assistant. He helped Liz Shaw and the Third Doctor decode an alien message. He was secretly working for General Carrington and warned him that the Doctor and Liz were getting close to decoding the message. (TV: The Ambassadors of Death)
Behind the scenes
The character was originally named Dawson until a member of the production team realised there had been a character named Dawson in the previous story. (INFO: The Ambassadors of Death.