Communications Daily October 30, 2003
Satellite Operators Expect Minimal Impact From Solar Flares
By Jeanene Timberlake
Satellite operators said they had taken precautions against the solar flares expected to affect satellites and communications systems on Earth this week, but most said the best precautions were taken when the satellites were manufactured. Solar flares are highly energetic eruptions on the surface of the sun that explode in all wavelengths of energy, from Gamma rays to simple heat, said Kelly Doser, space weather forecaster at the NOAA Space Environment Center (SEC).
Solar flares can have a number of effects and take place all the time, Doser said, although not at the current level. "The satellite and technology industries continue to be impacted by these things," he said: "But the user and the consumer on the ground is not seeing them as much any more due to engineers and technological developments [creating] ways to mitigate problems."
Charles Vick, senior fellow and contract consultant at Globalsecurity.org, said the worst problem solar flares could cause would be a complete shutdown of a satellite: "It could totally disrupt the... electronics themselves... creating a short circuit overload."
Satellite operators we talked with said there had been no reported problems with the satellites, but they would continue to monitor them. "We take these phenomena into account when we design and test the satellites. They're built to withstand the effects," an Intelsat spokeswoman said. She said the company used computers to filter out interference during communications with the satellites: "We also don't issue any kind of extraneous instructions to the satellites at this time. We figure out any housekeeping issues and do it ahead of time or do it later." A Loral spokeswoman also said the company kept its satellites at a minimum number of maneuvers.
DirecTV said it never had experienced an interruption of any kind due to solar flares or other electromagnetic activity. A spokesman said the company would continue monitoring the health of the satellites but it would be nothing out of the ordinary: "Our satellites were designed and built to withstand just about anything that deep space can dish out."
A spokeswoman for the Air Force Space Command (AFSC) in Colo. said the GPS satellites also were protected. Aluminum shields protect their electronics from radiation, she said, in addition to primary redundancies that kick in if a component fails: "This is something satellite operators deal with all the time, but not of this magnitude." While there could be interference with the signals, she said, AFSC is "expecting minimal impact because of the radiation shielding. If something did happen, other satellites can be moved into place." GPS uses a 24-satellite constellation, but has 28 in orbit.
Vick said the Dept. of Defense required its satellites, including GPS, to have radiation protection shielding, encasing electronic components with materials that would deflect a load. He said some satellites also were programmed to rotate their positions to defend against the flares. Vick said the military must have alternatives at all times: "If they don't have the hardware to do the job, they have a problem."
Flares are identified as 3 types -- radio waves, solar radiation and geomagnetic storms -- and they appear in that order, he said. Of the 3, radio waves have the least effect on satellites because the birds have to "see" the sun, he said: "If the sun's not there, [radio waves] generally won't have an impact." He said the impact of radio waves during this particular solar flare took place Tues. and lasted 12-15 min.
Solar radiation and geomagnetic storms are potentially the most damaging to satellites because of the energy of the particles, Doser said. Solar radiation particles can arrive min. or hours after an event, traveling at 93 million miles per hour, he said. At that speed, the particles can penetrate metal and insulated material and even get into circuitry, causing a single event upset, Doser said, making the satellite think it's supposed to do something.
For example, certain satellites track stars to determine whether their location is correct. "These particles can look like a star, and they don't come one at a time. So all of a sudden, this star tracker will try to adjust its orbit" based on the electronic particles, Doser said. The worst case scenario is that a satellite can get lost. Solar panels and energy collection systems also can be affected, Doser said, by degrading the solar collection cells, reducing the efficiency of the panels and decreasing the lifetime of the satellite.
The geomagnetic storms take the form of a lower energy plasma that can build up on the surface of a satellite, Doser said. If there's enough of a buildup, a trigger -- such as sudden changes in the amount of energy hitting certain parts of the spacecraft -- can cause a discharge and problems with orientation, he said. Geomagnetic storms also can alter the magnetic field that surrounds the earth, pushing the field closer to the surface and exposing satellites that might otherwise be protected, Doser said: "If the field is compressed at all, the satellites go outside the magnetic field and it can cause the discharge."
Each satellite has a different response time to the different parts of the flare, Doser said, depending not only on manufacturing, but also on how the satellite is positioned: "It depends on how it is flying and the affected crosssectional area. If something is flying in the wind, it will collect a lot of wind, but it can cut through if flying at an angle." Doser said the flares could take up to 3 or 4 days to have an effect on different systems.
© Copyright 2003, Warren Publishing, Inc.
