WASHINGTON — The first of four next-generation U.S. civilian geostationary weather satellites will now launch in October 2016, about six months later than planned, a spokesman for the National Oceanic and Atmospheric Administration said Oct. 15.

The delay means NOAA will have to depend in some capacity on the aging GOES-13 for at least a year beyond its 10-year design life.

The latest launch delay stems from unspecified issues with the Geostationary Operational Environmental Satellite (GOES)-R spacecraft itself, NOAA spokesman John Leslie wrote in an Oct. 15 email. This is the second slip for the satellite since its launch contract was inked in 2012, at which time GOES-R was scheduled to lift off this month.

Lockheed Martin Space Systems of Denver is building four GOES satellites for NOAA under a $1.4 billion NASA contract signed in 2008. NASA is NOAA’s procurement agent for spacecraft and launches. The Lockheed-built GOES satellites will keep watch on U.S. coastlines through 2036 at a cost of about $11 billion to NOAA.

Following its first launch slip, which in late 2014 NOAA blamed on difficulties with the satellite’s software and communications equipment, GOES-R was supposed to lift off no later than March 31, 2016. Then, earlier this month, Lockheed, NOAA and NASA realized they could not finish building and testing the satellite in time, Leslie wrote.

“NOAA, NASA and Lockheed Martin identified schedule risks,” wrote Leslie, without identifying the specific issues behind the risks. He did say, “NOAA decided it could best mitigate the impact of these risks by moving the launch date from March 2016.”

United Launch Alliance of Denver has a $446 million contract to launch both GOES-R and GOES-S, which is slated to lift off by June 30, 2017. Both satellites will launch on Atlas 5 rockets from Cape Canaveral Air Force Station, Florida. GOES-T and GOES-U, the final two satellites on Lockheed’s $1.4 billion GOES prime contract, will respectively launch in 2019 and 2024, according to a notional flyout schedule NOAA posted online in April. NASA has not yet awarded launch contracts for GOES-T or GOES-U.

NOAA operates three GOES satellites: one over the U.S. East Coast, one over the West Coast, and one that idles in a storage orbit as a backup in case something goes wrong with the other two.

A launch delay for GOES-R, therefore, would not immediately result in a loss of U.S. weather coverage. However, the longer NOAA waits to launch GOES-R, the longer the agency will have to rely on the aging GOES-13, which has already suffered some loss of instrument sensitivity from solar flares, according to NOAA’s website.

When GOES-R was still on target for an October 2015 launch, NOAA had planned to retire GOES-13 in April, according to a U.S. Government Accountability Office report published in February.

But after the GOES-R launch slipped for the first time, the agency decided to keep the 9-year-old GOES-13 in service as GOES East until mid-2016, according to an official GOES program schedule NOAA posted online. The document, dated April 21, is signed by Steve Volz, NOAA assistant administrator for satellite services.

GOES-13 launched in March 2006 and would be about six months past its 10-year design life by October 2016. Even if GOES-R does launch in October 2016, it will take NOAA another six months after launch to verify GOES-R is healthy on orbit, Volz said in an April presentation at the annual NOAA Satellite Conference.

All three GOES satellites now on orbit, which were built by Boeing, have a 10-year design life, plus fuel for about another five years. GOES-15, which launched in 2010, is the newest and currently operates as GOES West. GOES-13, the oldest, is GOES East. GOES-14, which launched in 2009, backs up the other two.

Backups have come in handy for NOAA, as in 2013, when a tiny meteorite struck GOES-13 and tilted it out of alignment. GOES-14 took over watch of the U.S. East Coast from its storage perch while NOAA steadied GOES-13, which returned to operational duty about three weeks after the strike.

When GOES-13 was out of service, it stayed in its East Coast orbit to conserve fuel. Once GOES-13 is out of fuel, it will not be able to maintain its weather-watching orbit, even if its attitude control system remains healthy and allows the spacecraft to point its instruments at the correct angle.