BeppoSAX takes the plunge
BY STEPHEN CLARK
Updated: April 30, 2003
A defunct Italian research satellite fell from orbit Tuesday and spread debris across the Pacific Ocean, ending a potential scare to more than 30 nations along the equator that were under the craft's orbital flight path before re-entry.
"Based on the American Space Surveillance Network assessment, the estimated ground impact time for the BeppoSAX main debris was April 29, 22:06 UTC, with an uncertainty window of plus or minus 7 minutes," Italian space officials announced early Wednesday.
Wire reports indicate most of the surviving debris landed in the Pacific Ocean about 200 miles northwest of the Galapagos Islands.
"No visual report concerning the satellite reentry time and area is at present available," the Italian statement went on to say.
Shut down one year ago Wednesday due to several spacecraft system failures and a rapidly decaying orbit, the BeppoSAX satellite's orbit hugging the equator was gradually lowered naturally by minuscule amounts of atmospheric drag present at orbital altitudes.
In the final weeks before taking its uncontrolled dive into Earth's atmosphere, the Italian Space Agency issued warnings to a number of countries near the equator that could have been the landing point as BeppoSAX plunged back to Earth. Officials were able to pin down a narrow impact zone about 4.36 degrees north and south of the equator because BeppoSAX's orbit had a low inclination that never ventured far from the equatorial belt.
In all, 39 countries initially received notice of the possibility of BeppoSAX debris landing on their soil. Nations in South America, Africa, Asia, and the Pacific Oceania made the list, which was refined shortly before the re-entry to include only 30 countries. Just hours before the event, another announcement again narrowed the list to 17 countries, discounting others as it became more clear where pieces of the beleaguered craft would end up.
Approximately 10 to 40 percent of most re-entering spacecraft survive to reach the ground, said Dr. William Ailor, the Director of the Center for Orbital and Re-entry Debris Studies at The Aerospace Corporation. Italian engineers said they expected about 47 percent of BeppoSAX to impact the ground or ocean, mainly due to several components made of stainless steel and titanium, which hold together better against the intense high-speed entry into the atmosphere.
By comparison, less than 40 percent of space shuttle Columbia's dry weight has been recovered as the organized search effort for debris winds down in Texas.
Officials said the surviving fragments would be in the form of about 42 pieces, the heaviest being about 265 pounds in weight. The remains of BeppoSAX were predicted to fall within a "footprint", or box, that stretched about 320 kilometers long and about 84 kilometers wide. They also estimated there was a one-in-five thousand chance of injury because of the uncontrolled fashion of the re-entry.
Also in their extensive studies of the BeppoSAX re-entry, Italian experts calculated that pieces left over would impact Earth at velocities ranging from 60 kilometers per hour to about 460 kilometers per hour.
In terms of weight, about 1,400 pounds of BeppoSAX was expected to survive intact. About 57 pounds of toxic hydrazine propellant is reported to be still aboard, which prompted the project office to warn the population of potential hazards with any debris that fell on ground.
BeppoSAX was launched seven years ago Wednesday from Cape Canaveral, Florida, aboard an Atlas 1 rocket.
Since then, the 3,100-pound satellite has monitored X-ray radiation from cosmic sources both inside and outside our galaxy by way of conducting almost 1,500 varied observations and finding over 50 gamma ray bursts, believed to be the most powerful explosions in the universe.
Its work received accolades from scientists around the world, including an award from the American Astronomical Society in 1998.
The highly successful mission was ultimately ended April 30, 2002, because of battery degradation and an orbit that was quickly becoming lower due to the effect of atmospheric drag.
The BeppoSAX observatory operated for six years from 1996 to 2002.
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