Sun-Earth Connection Education Forum Podcasts
Transcript of STEREO: introduction to the mission
The sun is anything but a stable yellow ball in the sky. Every day storms and explosions rage in the solar atmosphere and these enormous bursts of hot plasma are hurled out into space. Sometimes Earth gets in the way.
That's where NASA's new STEREO mission comes in. The Solar Terrestrial Relations Observatory is designed to observe these blasts, also known as coronal mass ejections or CMEs, from the sun in three dimensions.
Terry Kucera, STEREO Deputy Project Scientist: "Right now we can only see the sun, essentially, in just two dimensions. And with that there's really a lot we can't tell about coronal mass ejections. It's really basic: we can't tell for sure in some cases whether coronal mass ejections are moving towards us or away from us and that's really pretty fundamental. With 3-D, we'll really be able to understand what the trajectory of a coronal mass ejection is and with that we'll be able to tell just basic things like how fast is it going - is it speeding up or slowing down, and these are important things that we need to know if we're going to be able to predict what the impact of a particular event are going to be."
The effects of these solar storms on astronauts as well as Earth and its technologies is staggering.
Mike Kaiser, STEREO Project Scientist: "CMEs can cause a big electrical disturbance. They have associated with them some very high-energy particles. They could conceivably cause very big problems for astronauts, especially an astronaut that's outside the Earth's magnetic field - let's say on his way to Mars. The big CME with some of these associated particles comes along - he really needs to be inside that spacecraft and protected from this radiation. More generally CMEs affect everything that depends on microelectronics that's up in orbit like our GPS spacecraft that tell us positions on Earth, our cell phone communication, and other spacecraft that have microcircuits. If you know one is coming you can take preventative actions like put them in safe mode or something like that, and nothing bad will happen, but it can conceivably knock out the spacecraft."
STEREO consists of two nearly identical spacecraft. One flies ahead of the Earth, one behind.
They were built by the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, and tested at the NASA Goddard Space Flight Center in Greenbelt, Maryland.
Nick Chrissotimos, STEREO Project Manager: "Trying to integrate all of that on one spacecraft is usually difficult, but with two spacecraft it's even more difficult, more challenging, and in fact more fun from a standpoint of an engineer because we always want to do something different than we did previous times. This was quite exciting for a lot of us ..."
The spacecraft launch stacked on top of each other. Once in space they separate and use the moon's gravity to get into their respective orbits. They consist of a billion tons of matter traveling at a million miles an hour and are associated with solar flares. They usually take two to four days to reach Earth-useful time to heed warnings from solar observers.
But solar energetic particles, which are probably caused by CMEs, move much faster than the solar wind or the CMEs that generate them. These particles can reach Earth as soon as 20 minutes after the start of the storm, making them harder to forecast. Among other things including damage to satellites, high-speed solar particles pose a significant threat to astronauts.
Mike Kaiser, STEREO Project Scientist: "STEREO helps here because the astronauts really need to know and need to have warning of when one of these big storms is going to happen so they can be in one of the deepest parts of with the most shielding around them because you don't want to be out doing an extra vehicular activity when one of these storms hits. We had a storm in January 2005 that was very, very intense and I think if the astronauts had been out doing some extra vehicular activity on their way to Mars, they could have gotten a year's worth of radiation dose in just a few minutes. So STEREO and missions like that that are going to predict solar storms are extremely important."
When STEREO launches in Summer 2006, it will join a host of other missions that monitor the Sun-Earth interactions. These include the now legendary SOHO, which tracks overall solar activity, and Polar, which studies the behavior and nature of auroras-the so-called northern and southern lights-created as high speed particles interact with Earth's magnetic field.
Produced by Rachel Weintraub/NASA
