This month one could celebrate-- though few will--the 10th anniversary of Richard M. Nixon's first visit to Moscow. That visit inaugurated the era of d,etente, and if it had lived up to its initial promise, 10 years of d,etente would have been a lot to celebrate.

Instead we have a lot to mourn--for example, Yuri Orlov. Yuri Orlov is a human victim of the d,etente that never really materialized. He made the mistake of taking the promise of better East-West relations too seriously.

Today Orlov is an inmate of a Soviet prison camp. His wife and friends fear he has contracted a virulent, lethal tuberculosis that could end his life. This is his reward for contracting a different disease years ago, a virus that infects only minds, not bodies. For want of a proper medical term, we could call that virus freedom.

May 1972 was an exciting time in Moscow, particularly for Russians who ached to see their isolated country join the rest of the world for the last quarter of the 20th century. Yuri Orlov, a physicist, was one of those Russians. A small man of intense energy and great humor, he had just moved back to Moscow after a semi-voluntary internal exile in Armenia, where he had spent 15 years.

Orlov had a way of getting into trouble for speaking his mind. In 1956, after hearing about Nikita Khrushchev's famous "secret speech" denouncing Stalinism, Orlov had spoken out in a Communist Party meeting (he was a member) at the Institute of Theoretical and Experimental Physics, where he worked. He had criticized past party practices as anti-democratic, and pleaded for change.

Orlov's remarks were received enthusiastically by his colleagues, but party bureaucrats attacked him viciously and saw to it that he lost his job and could not find another one in Moscow. He ended up moving to Armenia, where he eventually did so well that he was elected to the Armenian academy of sciences.

When he returned to Moscow in 1972, Orlov was palpably excited by the atmosphere he found. He was fascinated by the public struggle then going on between the Soviet state, on one side, and Alexander Solzhenitsyn and Andrei Sakharov on the other. And he was intrigued that he could meet and talk with foreigners--a novel experience.

Orlov was drawn increasingly into activist dissident behavior. After the Helsinki agreement on European security was signed in 1975, he became a member of the "Helsinki Watch" group in Moscow, an informal organization of dissidents who declared themselves monitors of Soviet compliance with the humanitarian provisions of the agreement. For more than a year this group was able to distribute its findings on alleged Soviet violations of Helsinki's "Basket 3" on human rights.

Then Jimmy Carter came into the White House trumpeting his concern for human rights. Carter quickly wrote a personal letter to Sakharov and sent it through the diplomatic pouch, an affront to the Soviet leaders which infuriated them. On Feb. 8, 1977, Carter told a press conference he saw no connection between his speaking out on human rights in the Soviet Union and the strategic arms limitation talks he wanted to conduct with the Soviets. Two days later, as if to demonstrate that they, too, saw no connection, the Soviet authorities arrested Yuri Orlov.

There followed a trial on charges of anti-Soviet agitation. It was a classic example of Soviet jurisprudence.ires the Un

Orlov was sentenced to seven years in a "strict regime" labor camp, plus five years of internal exile in a remote corner of the country.

Of the four years since, Orlov has spent two in punishment cells and special prisons, often on a diet of 1,700 calories a day (about half what a man of 57, like Orlov, ought to have). He has been punished for continuing to protest, mostly against prison conditions. In camp and prison Orlov has had one medical problem after another. Doctors have told him he should not expect to live out his sentence, once even telling him, wrongly, that he had cancer. He has had kidney and prostate problems, bad teeth, low blood pressure, rheumatism, cystitis, chronic headaches from an old injury, and more. The news that he now has active tuberculosis reached Orlov's wife in Moscow from relatives of fellow prisoners who had recently visited the camp where he is currently being held.

Orlov has survived all this with his courage and spirit intact, as far as we know. His letters to his two sons and his wife (he is permitted very few, all of them censored) are full of enthusiasm for life, for Russian literature, for the struggle he continues to wage.

In one of those letters Orlov, a great nature-lover like so many Russians, described the barren surroundings. "Regretfully there are no trees here," he wrote."But I still walk a lot on the ridges, and in one corner (of the compound) there is a spot with pure water, and in the water there is beautiful green moss. I looked at it for long spells during the first, always dreary days. The Japanese watch their tiny gardens in the same way, which brings comfort to the spirit." That green moss may comfort Yuri Orlov's spirit, but it does little for those of us who knew him in a world where trees are plentiful, but men of Orlov's qualities are rare.