Compton's Deorbit Puts Jets and Ships at Risk By Mary Motta Senior Business Correspondent posted: 11:02 am ET 02 June 2000 Scientists Prepare to Deorbit Compton Satellite WASHINGTON – If all goes well when NASA deep-sixes its ailing astronomical satellite next week, the bus-size spacecraft will fall harmlessly into the eastern Pacific Ocean. But just in case the 17-ton (15,422-kilogram) Compton Gamma Ray Observatory (CGRO) careens out of control, those vulnerable to its scorching bits of debris -- mariners and pilots -- will have been warned. NASA's Goddard Space Flight Center in Greenbelt, Maryland, has started a plan to inform commercial airlines, the Coast Guard and other federal agencies when and where to expect CRGO to reenter Earth’s atmosphere. "We began dialogue about two months ago," said Preston Burch, deputy associate director for space science operations at Goddard. Because of a failure of one of its guidance systems, NASA has decided to "deorbit" CGRO in an effort to avoid having it fall onto a populated area. The $557 million spacecraft was launched in 1991. Goddard began warning the Air Force, the National Imagery and Mapping Agency’s World Wide Navigation Warning Services, the Federal Aviation Administration (FAA) and the U.S. Coast Guard in April that CGRO was expected to come in over the east central part of the Pacific Ocean. The agencies received a three-page letter that outlined NASA's plans for nudging the spacecraft out of orbit. "It is of paramount importance to protect life and property from the hazard of CGRO reentry debris. The CGRO debris is a significant potential threat to the safety of any aircraft or surface vessels in the debris impact area," the letter said. The impact zone for the so-called "controlled reentry" of the observatory covers a rectangular area 16.1 miles (26 kilometers) wide and 963.7 miles (1,552 kilometers) long. That area is about 1,100 miles (1,770 kilometers) from any land area. These "hot and fast chunks" will range from paper-thin debris to 15- to 20-pound (7- to 10-kilogram) chunks that will be falling several hundred miles (kilometers) per hour, Burch said. That could cause potentially devastating damage to a jet flying en route in the Pacific. The debris could slice off a wing or drill a hole through an airliner's cabin causing the plane to explode. Big chunks could also put a hole large enough in the hull of a ship to sink it. But the FAA said that the chances of any of that happening are slim. "Over the Pacific there is so much airspace and so few aircraft that the chances of the debris causing harm is narrow," said the FAA's Bill Shuman. The number of flights in the Pacific over an 8-hour period is about 200. That compares to about 1,000 flights over the North Atlantic in the same period. And there are even less commercial flights for the area pinpointed for the Compton deorbit, Shuman said. Still, the agency plans to warn airlines through a "Notice to Airmen," or NOTAM. This message is delivered via satellite, through e-mail and via fax to carriers around the world who will be flying in that area from June 4-6. Each day, Goddard will send out a notice describing the location of the hazard area "to minimize loss of usable airspace and ocean area to aircraft and surface vessels," the warning notice said. There will be a total of eight debris-hazard areas that Goddard will target. These areas will be off limits for about 90 minutes each day, Burch said. The reentry business is an imprecise one at best because objects can survive and make it all the way to the ground, said Bill Ailor, director for the Center for Orbital and Reentry Debris Studies at The Aerospace Corporation in Los Angeles. "Generally speaking, it is not so easy to predict where they are going to come down," Ailor said. Objects typically enter the atmosphere at a blazing 6 miles (9.7 kilometers) per second and are often incinerated by friction with Earth's atmosphere. But materials designed to be heat-resistant often can survive the plunge all the way to the ground. "Typically what we look for are titanium spheres and objects made of stainless steel (to survive)," Ailor said. Glass also can survive. The bus-sized CGRO is made mostly of aluminum, titanium and stainless steel. But there is a positive side to this undertaking. Several U.S. agencies are interested in documenting the fall of the CGRO to better understand such issues in the face of an increasing number of commercial satellite launches. And if the 110-ton (111,760 kilogram) Mir space station doesn’t survive commercially and the Russians decide to take it out of orbit, such information will be critical to ground controllers plotting its reentry zone. "Mir has so much stuff on it that the debris field will be so much larger and more dangerous," Ailor said. <A HREF="http://www.ctrl.org/">www.ctrl.org</A> DECLARATION & DISCLAIMER ========== CTRL is a discussion & informational exchange list. Proselytizing propagandic screeds are unwelcomed. Substance—not soap-boxing—please! These are sordid matters and 'conspiracy theory'—with its many half-truths, misdirections and outright frauds—is used politically by different groups with major and minor effects spread throughout the spectrum of time and thought. That being said, CTRL gives no endorsement to the validity of posts, and always suggests to readers; be wary of what you read. CTRL gives no credence to Holocaust denial and nazi's need not apply. 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