Early warnings of falling Skylab

Press, 16 June 1979, Page 6

Early warnings of falling Skylab

By LBS BLOXHAM. travel editor Aircraft flying over NewZealand will receive ample warning of the possibility of! being nit by falling debris, from the doomed 85-tonne! Skylab space laboratory nextmonth. New Zealand and other countries in the re-entry path of the runaway craft have been warned by the National Aeronautics and Space Administration at Houston, Texas, to be prepared to alert aircraft if the areas under their control are in danger. Skylab is expected to plunge into the Earth’s atmosphere some time between July 4 and July 28, but scientists will not know exactly when and where the debris will fall until about 24 hours before. Captain M. E. McGreal, assistant director of flight operations with the Civil Aviation Division of the Ministry of Transport in Web lington, ha said that the N.A.S.A. warning had been received. N.A.S.A. will issue three

warnings 24 hours, 12 hours, and six hours before Sky lab hits the Earth. Captain McGreal said aircraft would have plenty of time to clear the danger zone. For New Zealand, this will extend along a 2000 km by 200 km strip which, at the most, would need to be doged for only 20 minutes. Jet aircraft could divert to the safety of one side or the other in about 12 minutes. Official notices to pilots would be issued by the Ministry, said Captain McGreal. ‘Some aircraft might also have to stay on the ground for a little longer than! planned if this space vehicle does decay over New Zealand,” he said.

According to an NZPAReuter report from Jerusalem, Israel has decided to close its air space entirely if there is an indication from N.A.S.A. that the wreckage i$ likely to fall in its area. Meanwhile, in Houston, scientists hope to alter Skylab’s rate of descent if the wreckage appears to be headed for a populated area. Controllers plan to shift Skylab on Monday to a posi-

tion where it can be controlled a short time before impact, said a space centre spokesman, Mr Charles Redmon.

“Twelve hours before impact, we can predict eight orbits forward as to where the debris will fall,” he said. “If it is going to fall over a populated area, we can change the drag (by shifting its position relative to its line of flight) and keep it up for several more orbits.”

Scientists have determined that pieces of Skylab will fall over a track 4000 miles (6400 km) long, 100 miles (160 km |wide, with a possible 50deg error both north and south. Some pieces could weigh several thousand kilograms, scientists say. Skylab was put into a 273mile (427 km high orbit after its launch in 1973. The latest Norad calculations last Thursday put the craft about 178 miles (285 km high.

The spacecraft, about the size of a three-bedroom house, would begin disintegrating wheri it hit the I Earth’s atmosphere, about 20 minutes before impact, Mr 'Redmon said.