Joseph E. Karth, 83, a Democratic congressman who represented Minnesota's 4th District for 18 years, died May 29 of a heart attack at his home in Scottsdale, Ariz. He had been living in Scottsdale since leaving Washington in the late 1970s.

Elected in 1959 to the seat formerly held by Eugene McCarthy, Mr. Karth served on the House Science and Aeronautics Committee and was chairman of its subcommittee on space sciences and applications.

Son Kevin Karth recalled in an interview that his father was a proponent of manned spaceflight until about the time of the Apollo program, when he came to the conclusion that the National Aeronautics and Space Administration was losing momentum. He began to advocate unmanned spaceflight as a safer alternative and better return on the investment.

Karth also noted that his father, a Minnesota Vikings football fan, named the Viking spacecraft, the first space vehicle to land on Mars.

Mr. Karth also was interested in environmental protection and was the author of the 1968 Wild and Scenic Rivers Act.

Mr. Karth was born in New Brighton, Minn., and studied at the University of Nebraska School of Engineering before leaving school to enlist in the Army. He served in Europe during World War II and afterward worked for Minnesota Mining and Manufacturing Co.

He organized the Oil, Chemical and Atomic Workers Union at the St. Paul-based company and launched his political career as president of the union. He served in the Minnesota House of Representatives from 1950 to 1958.

In Congress, he also served on the House Ways and Means Committee. After a heart attack forced him to retire in 1977, he established a consulting firm and became a lobbyist specializing in trade issues.

Mr. Karth's wife, Charlotte Karth, died in 1992.

Survivors include two sons, Brian Karth of Scottsdale and Kevin Karth of Portland, Ore.; a sister; and four grandchildren.