From the Traveller RPG Wiki on wikia.com:
David R. Deitrick is an artist. He produced many pieces of work for Game Designers' Workshop, including the covers for all of the Alien Modules and the Starter Traveller book.
In addition to his RPG work for Traveller, he has produced artwork for numerous other RPGs, Collectable Card Games, and board games. He continues to produce art works in a wide array of media and teaches art.
Many of his credits have his name misspelled as "Dietrick."