Saturday, June 6, 2009

Space Weather: What it is and why it matters

Communications Technology

The National Oceanic and Atmospheric Administration (NOAA) is predicting a mild solar storm season for the next 11-year solar cycle. (For the initial announcement, click here.) But what does that mean, and why do we care?

What it is

To simplify, space weather is electromagnetic stuff happening in space - usually involving the sun - that can affect us here on Earth. That can include such things as solar flares, solar storms, coronal mass ejections and solar wind. These can affect satellites, power grids and radio propagation.

"This whole concept of space weather is kind of an interesting one," said Ron Hranac, a technical leader at Cisco and CT's senior technology editor. "The sun can do a lot of good stuff for us ... but it can also do some interesting and some nasty things, like spit out huge storms that can have a pretty severe impact on things here on Earth, including the climate and technology."

As an aside, sun transit outages, sometimes mistakenly called "sunspot outages," are not space weather and have nothing to do with sunspots. Sun transit outages interfere with signals from geostationary satellites around the spring and fall equinoxes because of geometry. During the equinoxes, the orbits of the sun, Earth and geostationary satellites align such that a receive antenna on the Earth can't "see" the satellite because the sun is directly behind it.
What it can do

Of primary interest in telecommunications is space weather's effect on satellites and power grids.

"What happens in a space weather storm is, yes, there's a risk to satellites; yes, there can be interference at discrete frequencies; and there can be problems induced in the (power) transmission lines, which saturates the core of the transformers at the power stations, which then can make its way to the distribution network," said Doug Biesecker, a scientist with the NOAA's Space Weather Prediction Center.

Biesecker said geostationary satellites, via which many cable operators receive programming, are subject to RFI from the sun and that severe space weather can take out a transponder or entire satellite. He cites the following example.

"Telstar 401 in 1997, space weather, it was gone for good," he said. "Yeah, there are instances of satellites completely killed by space weather."

Losing the bird leads to a scramble to re-establish the programming it formerly carried, Hranac said.

"If a satellite gets damaged - permanently damaged - by a solar event," he said, "then the cable companies that are carrying those program services they are receiving by satellite would then have to point the satellite dish to another satellite that is operating in a backup capacity."

Power grids and railroad tracks, both essentially being very long conductors, are also at risk. A big solar flare in 1989 caused power outages in Canada that affected about 6 million people.

"There are surge currents, if you will, induced in those long conductors - railroad tracks, cross-country high-voltage transmission lines, and things like that," Hranac said. "These surges can, if they're severe enough, damage electrical equipment - transformers, substations, and other things. It essentially overloads this stuff, and it gets some pretty substantial surge damage."

What to do

Luckily, space weather events affecting satellites and power grids are rare. Because the sun is a sphere, relatively few solar events face the Earth, so most dissipate out into space. Still, it's wise to be prepared, Hranac said. Know the backup transponders and satellites for your programming and whether your dishes have a clear line of sight to them.

"There probably should be some kind of Plan B in place at the system level, or certainly at the corporate level of a cable operator," he said. "What are you going to tell your systems to do if the satellite carrying HBO goes out because of a solar flare? It may be one of those low priority things, but discuss it. Put together a Plan B; just be aware of it. Say, 'This happens, and this is what you do. This is who you call, here are the numbers, this is the information.'"

To learn more about space weather, check out the Web sites for the Space Weather Center and the National Weather Service Space Weather Prediction Center. *

- Ron Hendrickson
*Don't forget!