For the week starting Friday, Dec. 10. Times are E.S.T., subject to change.
Metropolitan Opera (Sat. 2 p.m., ABC). Tristan und Isolde, with Helen Traubel and Lauritz Melchior.
Invitation to Learning. (Sun. 12 noon, CBS.) G.I. Cartoonist Bill Mauldin discusses Eisenhower's Crusade in Europe.
RCA Victor Show (Sun. 5:30 p.m., NBC). Arthur Fiedler and the Boston Pops Orchestra, with Baritone Robert Merrill. Premiere.
Studio One (Sun. 7:30 p.m., CBS-TV). Gian-Carlo Menotti's opera The Medium, starring Marie Powers.
Talent Scouts (Mon. 8:30 p.m., CBS-TV). Arthur Godfrey moves into TV....