WASHINGTON -- Just a month after the government stored an extra weather satellite in space, the spare is being called on to replace an orbiting observatory that is failing.
"It's the first time we had ever had a backup satellite in place," said Gerald Dittberner of the National Oceanic and Atmospheric Administration.
"Without such a satellite, we would have had to wait as much as 12 to 15 months to get a launch time slot," said the program manager for stationary weather satellites.
Normally there are two stationary satellites collecting detailed weather data as well as the popular satellite weather pictures seen on television. One covers the West and the Pacific Ocean out to Hawaii; the other sees the East and Atlantic Ocean. Their views overlap in the nation's center.
When one of the two stationary weather satellites failed in 1989, the agency was forced to move the remaining one back and forth depending on the season -- west in winter to watch for storms from the Pacific, east in summer to seek out hurricanes. Eventually, the United States borrowed a European weather satellite to help.
The GOES-10 satellite, placed in storage in orbit in mid-June, was being activated Thursday. Launched last year, it underwent lengthy tests before being placed in storage. GOES stands for geostationary operational environmental satellite.
"Now we can have GOES-10 transmitting data within 72 hours after activation, meeting our program needs without any loss in data continuity," Dittberner said.
GOES-9, the western satellite, is showing signs of impending failure of the control system that keeps it stable.
"Both momentum wheels on GOES-9 have exhibited problems," said Kathleen Kelly, director of NOAA's Satellite Operations Control Center. Momentum wheels are like gyroscopes, helping to keep the satellite stable.
"We need at least one wheel in operation to maintain pointing accuracy," she said. "Though we expect it to fail at any time, we are doing our best to keep GOES-9 transmitting until GOES-10 becomes fully operational within the next week."
GOES-10 was parked over the center of the country and moving it to the West Coast location will take about 30 days, Ms. Kelly said. But it will be observing the weather and taking measurements during that gradual shift, moving about 1 degree of longitude per day.
The current GOES satellites, GOES-8 and GOES-9, were the first in a new series that had projected lifetimes of three years. GOES-8, launched four years and two months ago, continues to function. GOES-9 was launched in May 95. The planned life of GOES-10 is five years.
The next satellite in the series, GOES-L, is scheduled for launch in May 1999 and will be stored in orbit.
These satellites orbit about 22,300 miles above the Earth, moving at a speed that keeps them in place over the same spot on the surface at all times.