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Hurricane Dennis might have steered clear of the launching pad of space shuttle Discovery. But, as this ScienCentral News video reports, the astronauts leaving earth have a different kind of weather to worry about after liftoff — space weather.
Here Comes the Sun
On earth we worry about hurricanes, blizzards, tornadoes, and so on. But in space astronauts have other concerns: solar flares, radiation storms, geomagnetic storms and energetic electron charges. A great deal of this kind of nasty weather is caused by the sun, which blasts billions of tons of electrically charged particles throughout the solar system on a regular basis.
"So we actually go to work like a regular weather person, except we look at the sun, and the 93 million miles between the sun and the earth," says Bill Murtagh, space weather forecaster for the National Oceanic and Atmospheric Administration (NOAA). "We have several satellites out in the near earth environment measuring the weather, if you will. We actually look at the surface of the sun to see sunspots. Sometimes they're large complex sunspot groups that may produce eruptions. When these eruptions occur they have a significant effect on the near-earth environment, on space based technologies, such as satellites, GPS operations, deep space NASA missions."
When it comes to the astronauts undertaking Wednesday's mission STS-114 on space shuttle Discovery, conventional wisdom tells us they have little to worry about since we're in what's called "solar minimum" — the quiet period of the sun's 11-year cycle. But Murtagh says there's no guarantee.
"It's kind of a misnomer and misunderstanding out there in the community... this period that they call 'solar maximum' and 'solar minimum'. Solar maximum is typically that two to three year period where we see the most sunspots on the sun and consequently the most solar flares, solar eruptions, and the most space weather storms. Well that is true. But during the waning stages during the solar cycle — that three, four, even five year period past the sunspot maximum — we continue to see sunspot groups, just not as many."
He says that while there may be fewer sunspots during solar minimum, those that do emerge can be quite potent. He recalls the unexpected and surprisingly powerful "Halloween storms" of late October and early November of 2003.
"Typically we're used to — in regular weather — we've got blizzards, we've got hurricanes, and we've got tornadoes," he says. "Well, imagine them happening all at the same time. That's kind of what we were seeing at this particular period."
image: NASA
The radiation from those storms was high enough to send astronauts onboard the International Space Station into extended hiding in a specially hardened area of the space station that's most protected from radiation.
He also mentions a solar storm that emerged in January of 2005 and produced one of the most intense proton storms in decades that, according to a NASA statement, shook the foundations of space weather theory.
"So yes, we see less sunspots in the waning stage of the cycle," Murtagh says. "However, every so often we get these rogue, if you will, spot groups, large sunspot clusters that will form late in the solar cycle and produce very significant activity."
But even if the astronauts aren't put in harm's way themselves, their communications systems might. That's because while we're in solar minimum, we're also in what's called the energetic electron maximum.
"One of the things we've worried about in the past has mostly been electromagnetic radiation and high energy protons, but what we've come to discover is that energetic electrons are also a danger [because they] pose a danger to the operation of satellites," says Alex Young, a solar scientist at NASA. "And what happens is these energetic electrons exist in space coming from the sun and they charge up satellites just like you would rub your foot across the carpet and charge up static electricity. Well eventually this will cause a discharge within the satellite."
When this discharge happens, the satellite shorts out and loses communication. Young thinks the astronauts should have enough back-up satellites to withstand charges like this without losing communication completely, but he says it's possible. "We really don't have any understanding yet of the details of when this discharge will occur, how long it takes for it to build up in a satellite. So these cause anomalies which we don't have a lot of ability to predict."
As someone who watches the sun on a daily basis, he says there's heightened urgency during a shuttle mission: "We certainly don't want satellites to malfunction, we don't want communications systems to go down that would jeopardize the launch, and we also don't want the astronauts to be in a position where they're exposed to high energy radiation while they're traveling to the International Space Station."
But at this point, both he and Murtagh agree that predicting space weather isn't any easier than watching the shores of Cape Canaveral Florida, home of the space shuttle, where forecasters can never be sure when a tropical depression in the ocean will turn into a full blown hurricane that will hit land.
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