NewsSeptember 24, 2012

Key Weather Satellite Goes Offline, May Affect Forecasts

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Andrew Freedman

By Andrew Freedman

In the midst of the very active North Atlantic hurricane season, the main weather satellite scientists use for keeping tabs on the weather across eastern North America and the Atlantic Ocean has gone offline. The outage began late on Sept. 23, after a period when the satellite, known as GOES-13, had been experience increasing vibrations, or “noise,” in particular instruments that was degrading its performance. According to the Capital Weather Gang blog, the satellite was put in stand-by mode while engineers work to fix the problem from the ground. 

Illustration of a GOES Satellite.
Credit: NOAA.

In the meantime, NOAA has taken action to maneuver a spare satellite into service. According to a message on NOAA's website, there is no estimated time that the malfunctioning satellite will resume service. 

The outage of this geostationary satellite — so named because the satellite stays in a fixed orbit above the equator — does not mean that forecasters are flying blind, and have lost all of their imagery sources for the Atlantic and East Coast, however.

At first, NOAA placed a satellite that covers the West Coast — known as GOES-15, into “Full Disk Scan” mode, which will allow it to take pictures of eastern areas once every half hour. According to a post on the University of Wisconsin’s satellite blog, polar-orbiting satellites can also make up for some of the lost imaging capability, but they cannot take images of the North Atlantic and eastern U.S. as frequently as the GOES-13 satellite did. 

In a move indicative of the potential for the GOES-13 outage to continue, NOAA has now placed its backup GOES satellite, known as GOES-14, into service to take over for the troubled GOES-13. However, GOES-14 is not yet providing all of the data that the malfunctioning satellite was contributing.

“GOES-14 will remain the primary GOES satellite over the Atlantic basin and Continental U.S. until the imager and sounder data issues on GOES-13 can be fully diagnosed and hopefully fixed,” NOAA said in an online statement. “NOAA maintains backup GOES satellites in case unforeseen events occur, providing full redundancy for monitoring severe weather over the U.S. and its territories.”

Launched in 2006 but not put into service until 2010, GOES-13 should have several more years in service before it reaches the end of its design lifespan. 

One of the biggest impacts from the brief degradation in satellite coverage could be felt in the area of computer modeling, since satellites are one of the main data sources for weather models. This could have an impact on the reliability of hurricane forecasts in particular. As of Monday, there was one tropical system in the Atlantic, Tropical Storm Nadine, located in the eastern Atlantic, well away from land, and within GOES-13's coverage area.

A satellite image taken by GOES-13 before it was placed in standby mode, showing some of the interference, or “noise,” that was affecting its imagery. Click on the image for a larger version.
Credit: CIMSS Satellite Blog.

NOAA spokesman John Leslie said that the absence of certain types of data typically provided by GOES-13 could degrade the accuracy of some computer model projections by a small amount. “The loss of temperature and moisture data used in numerical weather prediction models and guidance to forecast centers and offices is relatively small because this information also comes from polar satellites and radiosondes [weather balloons],” Leslie said in an email to Climate Central. “The loss of image-tracked wind data over the ocean might cause a slight degradation in the models because there are no other sources of the data. Wind data derived from GOES 14 will need to be tested before being substituted on an operational basis.” 

The loss of GOES-13, even if it is temporary, may give forecasters a preview of what lies ahead due to delays in the development of the next generation of polar-orbiting satellites. The delays mean that the polar satellite program won't have the redundancy that is present in the GOES program.

Polar-orbiting satellites continuously scan the planet from north to south, and instruments aboard these satellites are used for many applications in addition to weather forecasting, such as monitoring volcanic eruptions, gathering sea surface temperature data, and locating emergency beacons from aviators or mariners in distress.

NOAA has warned that, starting in 2017, there will be at least a year long gap between the newest polar orbiting satellite’s design lifetime and the scheduled launch date of its replacement.

That would mean the U.S. would be reliant on just one polar-orbiting satellite, rather than the two that have long been in service. NOAA ran up billions in cost overruns for the next generation of polar-orbiting weather satellites, and delays and a lack of funding from Congress have put that program, known as the Joint Polar Satellite System (JPSS), years behind schedule.

NOAA has warned that such a data gap could significantly erode the agency’s ability to provide advanced notice of significant weather events, such as the “Snowmageddon” blizzard of 2010. The GOES-13 outage also comes soon after an independent NOAA review team criticized the agency’s oversight of its weather satellite programs, according to an article in Aviation Week and Space Technology.

NOAA's Leslie downplayed the significance of the GOES-13 malfunction. “To put it into perspective, this is a technical anomaly, which is not unusual during the life of any satellite mission. NOAA continues to work with its partner, NASA, on the development and launch of the next-generation JPSS and GOES-R satellites,” he said.