Joan Jonas is a ''performance artist'' -- not an actress or a director, exactly, but an artist whose media happen to be stage and videotape. As such, she is less interested in traditional theater and television than in personal exploration. Earlier examples include her intense solo show, ''The Juniper Tree, '' based on the Brothers Grimm, and her offbeat videotape, ''I Want To Live in the Country.''
Her latest work, a futuristic fable called ''Double Lunar Dogs,'' appeared recently at the Performing Garage in New York and has since been videotaped with help from a Rockefeller Video Fellowship. Based on the classic story ''Universe'' by Robert A. Heinlein, it takes place on a spaceship that has been in transit for so many generations the inhabitants have forgotten its origin and mission.
Miss Jonas uses this fascinating conceit for purposes quite different from Heinlein's, stretching the tale's themes and motifs into very personal shapes and sizes, knitting them into a psychodrama that's lightened by comic touches.
As concocted by Miss Jonas and collaborator Jill Kroesen, the show has some striking effects and images; and cast member Spalding Gray is marvelous as a gentle spaceman.
But the work has aspirations to storytelling - however secondary this may be - and Miss Jonas regrettably neglects this aspect of her assemblage. The result is audacious but incomplete.