The Soviets have become more open about announcing their space failures, but failed to announce the destruction of a spy satellite last month and gave out sparse details about a rocket failure, space-watcher Jim Oberg said Saturday. The official Tass news agency reported that the upper stage of the Proton rocket booster failed on Wednesday and that on Thursday ``the Sputniks entered dense layers of the atmosphere and ceased their existence.'' According to U.S. Space Command, the largest chunk of debris from the mission re-entered the earth's atmosphere Friday afternoon between Saudi Arabia and Turkey, and a smaller chunk fell earlier near Australia. Besides the failure of the Proton, with three satellites aboard, the Soviets lost another satellite, Cosmos 1,906, on Jan. 31. The imaging satellite was launched on Dec. 26 and was ``blown up to prevent the film and equipment from falling into the hands of western intelligence agencies,'' Oberg said. Since Soviet leader Mikhail S. Gorbachev came to power in March 1985, Oberg said, the Soviets ``have certainly released new material. But there remain severe limits. Military stuff is clearly beyond the limit.'' Still, Oberg said, Western technology can detect such events as the Proton failure, and Western news reports can force further disclosures from the Soviets. Penetrating the secretive Soviet space program is nothing new for Oberg, who has published his findings in a new book called ``Uncovering Soviet Disasters: Exploring the Limits of Glasnost.'' Long before Gorbachev's moderate reforms led to greater disclosure of problems in the Soviet Union, Oberg had pieced together hair-raising tales of disasters that for decades went unreported in the state-controlled media. Oberg has ``been working since childhood at this, watching their space program, looking for chinks in their secrecy, and driving through them.'' Soviet secrecy can be dangerous, Oberg wrote in his book. On Oct. 24, 1962, a Soviet space probe exploded into dozens of objects during the Cuban missile crisis, the confrontation that brought the superpowers their closest to nuclear war. Debris from the probe ``appeared without warning on American attack-warning radars in Alaska,'' Oberg wrote. ``The Cuban missile crisis was at its height, and for a few moments the unannounced and unpredicted Soviet space failure looked like the long-feared massive Soviet (Intercontinental Ballistic Missile) attack.'' The debris burned up as it entered the atmosphere. But, Oberg said, the Soviets have never publicly acknowledged the event. Soviet media also have not reported on the most spectacular ``and probably the greatest disaster of the space age,'' the ``Nedelin catastrophe,'' which on about Oct. 24, 1960, killed scores of Soviets including Marshal Mitrofan Nedelin, the commander in chief of the Soviet Strategic Rocket Forces. The accident came three years after the Soviets launched the first satellite, ``Sputnik.'' Operating in the strictest secrecy, the Soviets launched two unmanned spacecraft on a probe to Mars, but both fell back into the atmosphere and burned up because their upper stages failed. A third booster was loaded with fuel, and the order was given to launch. But the main rocket engine did not ignite. ``It just stood there on the launch pad, bathed in searchlights and fuming with clouds of supercold liquid oxygen,'' Oberg wrote. ``Nedelin made a fatal error and committed a gross violation of elementary rocket safety standards,'' Oberg wrote. ``From the launch bunker, where he had prepared to watch the expected success, he ordered a team of engineers to inspect the rocket booster immediately. ...'' ``Since he was an experienced combat commander, he would not send men into peril he himself avoided, so he walked out to the base of the rocket while the inspection was being made.'' Although the main rocket failed to ignite, the uppermost stage continued to operate as though it were en route to Mars, and at the time when it would have separated from the booster, fired its own rockets. ``A million pounds of kerosene and liquid oxygen flared up in a pyre which must have been visible for hundreds of miles,'' Oberg wrote. The Soviet press carried an official obituary of Nedelin several days later, saying that he had ``died tragically in the line of duty'' in a plane crash. Not a word has appeared since then in the official press, although writings smuggled out of Russia or published by emgres have described the incident, and Oberg pieced together the evidence.