* Spare satellite activated, but not moved
* Troubleshooting efforts under way for GOES-13
* Satellite helps track weather off U.S. Atlantic Coast
By Irene Klotz
CAPE CANAVERAL, Fla., May 24 (Reuters) - A key satellite positioned to track severe weather in the eastern United States has failed, just as the 2013 Atlantic hurricane season is about to start.
The U.S. National Oceanic and Atmospheric Administration (NOAA) has activated a spare satellite, which will provide coverage of the East Coast, while tries to fix the failed one, the agency said in a status report on its website on Friday.
"There is no estimate on return to operations at this time," NOAA said.
The Atlantic-Caribbean hurricane season starts on June 1 and lasts six months. NOAA warned on Thursday that this year's season may be "extremely active," with 13 to 20 tropical storms and seven to 11 of those strengthening into hurricanes.
The agency's three current Geostationary Operational Environmental Satellites, known as GOES, were built by Boeing and designed to last 10 years. The failed spacecraft, GOES-13, was launched in 2006.
The same satellite was sidelined for about three weeks last year by another problem.
"At this time, it's too early to tell if it's related - it doesn't appear to be related," Tom Renkevens, a NOAA deputy division chief, told Reuters.
NOAA typically operates two GOES spacecraft over the United States, overlooking the East and West coasts, plus one on-orbit spare. The satellites are outfitted with imagers to watch for clouds and developing storms, atmospheric sounders to measure temperatures and humidity, and other instruments.
The first sign of trouble with GOES-13, the primary East Coast satellite, surfaced late on Wednesday when it failed to relay expected images, NOAA status reports show.
GOES-13 is located over 75 degrees west longitude. Though activated, the spare remains in its storage orbit at 105 degrees west. Data received from that spare and a European satellite, means that weather forecasters still have a full view of the Atlantic Ocean.
"We're not blind in any areas," Renkevens said.
If a second GOES should fail, NOAA would operate its remaining satellite in a different mode to get a full view of the United States every half-hour. The agency would also depend more on supplemental information relayed by polar orbiting weather satellites.
"That's never happened, but if something should happen we have plans," Renkevens said.
Efforts to troubleshoot the failed satellite are continuing and for now NOAA does not plan to drift its spare GOES east. Relocating the satellite takes about a month because it has to be moved very slowly so it can maintain a steady gaze on Earth, Renkevens said.
NOAA also has an older GOES-12 satellite, launched in 2001, parked at 60 degrees west that provides coverage of South America.
The first of the agency's next-generation GOES spacecraft is due to launch in October 2015.