Two Harvard Physics professors have cancelled upcoming trips to the Soviet Union in protest of last week's trial and sentencing of Yuri F. Orlov, a Soviet physicist and critic of Soviet human rights policies.

Nicholas Bloembergen. Rumford Professor of Physics, decided to cancel his planned three-and-a-half week tour of the Soviet Union in June, which included a lecture in Leningrad and visits to several laboratories around the country.

Bertrand L. Halperin '62, professor of Physics, is a member of a delegation of 19 U.S. scientists invited to attend a scientific symposium in Moscow this week. The delegates voted unanimously to cancel their visit after Orlov's sentencing.

Orlov whom Bloembergen called a "self-appointed watch-dog" for violations of the 1974 Helsinki agreement on human rights, received a seven-year prison sentence to be followed by a five-year exile from Moscow, during which he is not allowed to work as a scientist.

In a letter to the Soviet Academy of Sciences, Bloembergen stated that Orlov's trial, which the public and the press were not permitted to attend, and the harsh sentence he received "deliberately defy and violate" the Helsinki pact.

Bloembergen criticized the Soviet Academy for "its complete silence" about Orlov and other imprisoned dissidents despite "numerous expressions of concern and protest over the past year and a half" from the international scientific community.

By cancelling their visits the scientists are "signalling to the Soviet Union that they shouldn't take it for granted that these scientific exchanges will go on when they ignore our messages about violations of human rights," Bloembergen added.

Bloembergen, who has been to the USSR on two other scientific exchanges, had planned to give a lecture in memory of a recently-deceased Soviet scientist who was a "close friend and colleague." He now plans to pay tribute to the scientist in a lecture in Atlanta