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NASA is about to get a 'double dose' of the sun with a new space science mission called STEREO or, Solar Terrestrial Relations Observatory.

With the twin spacecraft observatories, scientists will soon get a never-before seen 3-D view of Coronal Mass Ejections which are explosions in our solar system. Here with some inside information about STEREO are Project Scientist Michael Kaiser, and Deputy Project Manager Jim Adams.

Gentlemen, thank you for joining us on NASA Direct.

Well, thank you very much for having us. It's a great opportunity to answer questions from people that have sent in on the Internet.

It's my pleasure to be here.

What is the main objective of the STEREO mission?

Well, the main objective is to try to make better progress on predicting when space weather events will reach Earth. The sun gives off these tremendous storms called coronal mass ejections, or CMEs, and the ones that we're most interested in are the ones that are coming right at us. And with the SOHO spacecraft and others sitting at Earth, it's particularly hard to measure those, 'cause you're looking right at them. And so what we're going to do with STEREO is place some spacecraft off to the side and basically triangulate these, so we'll get a much better handle on their speed and exactly when they will hit Earth. So we will be able to predict much better.

What is the difference between the SOHO and STEREO missions?

I guess I'll start and then Mike will pick up. I think the primary difference between STEREO and SOHO is that STEREO is two satellites looking at the Earth-sun connection from the side, whereas SOHO is a single spacecraft looking straight on between the sun and the Earth.

That’s true. SOHO is a, is a considerably bigger spacecraft than STEREO. It's probably bigger than both STEREOs put together, and has a much larger complement of instruments, but basically measures the same type of, type of things. SOHO has been up, they just had their 10th anniversary a few months ago. So it's been out there for a long time, and we hope it'll continue for a long time, because we will make use of it with STEREO.

Can the STEREO mission predict and let the crew on board the ISS know of CMEs to keep them from being exposed to harmful X-rays, gamma rays and so on?

Well, I think that the answer to that question is that NASA and NOAA are partners in doing space weather predictions, making space weather predictions. STEREO sees the, the large Earth-bound events and broadcasts them immediately to NOAA, where they're processed and distributed for everybody who's interested in space weather. At that point in time, ISS could pick up on a, an alert put out by NOAA in the event of a large CME.

Right. ISS, though, is probably not so particularly susceptible to these types of storms because it's, it's relatively close to Earth and deep inside Earth's protective magnetic field. So a lot of the space weather events literally don't get to it.

What kind of damage do CMEs cause? Are we able to predict CMEs getting to Earth?

It's mostly electrical damage these days. All of our spacecraft that are up there all have micro-electronics parts, and they're very susceptible to small, small voltage and current changes, and these, these storms have a, can induce a lot of, lot of that sort of thing and actually can cause spacecraft to shut down. So if you know one's coming ahead of time, you can take some preventive action. They've also been known on very big storms to actually trigger power outages on the Earth. There was a famous one in the late '80s in Canada that shut down the entire power grid; I think it was in Ontario, due to a solar storm. So there's been, this whole business of trying to predict when CMEs will arrive at Earth has, has been going on for a number of years. And as I said earlier, from a single spacecraft looking right at the sun, the ones that are coming at you are particularly difficult to measure. And so with STEREO, we're hoping to cut the error bar on our predicts, so to speak. Right now, we can probably only predict to plus or minus 12 hours. We're hoping to cut into that and do a much better job by triangulating from the sides.

Why is the temperature of coronal mass ejections so high -- several million Kelvins -- while on the other hand, the temperature of the sun is only 6,000 Kelvins?

One of the big enigmas of our time. In fact, surprisingly, one of the coolest places on the sun is the visible surface, the so-called photosphere, which is, indeed, about only 6,000 degrees, which sounds like a lot. If you barrel into the sun and go down into the center, it's about 35 million degrees. That's where the nuclear furnace really happens. But also, if you go up into the sun's atmosphere, into the corona, surprisingly, the temperature goes up to a couple of million degrees, and there's been a lot of argument on how this happens. And the current thinking is that all the magnetic field of the sun, all the little bubbling, magnetic bubbles on the sun, all propagate upwards into the solar atmosphere and carry heat with them, and heat, heat up the sun. So the coronal mass ejections, indeed, when they're near the sun are a few million degrees. Now by the time they get to Earth, they've cooled off considerably. So we don't have to worry about burning up, but it's, it's one of the ongoing problems in solar physics right now.

How will the two STEREO spacecraft be protected from exposures to harmful CMEs?

Well, the satellites have been carefully analyzed for their, for the impact of radiation on all of our sensitive electronics, as well as all of the surfaces have been coated with conductive coating that allows the satellite to not charge up differentially. So, if you think about the fact that coronal mass ejections, the solar wind and the photo-electric effect could cause the satellites to charge in one spot to kilovolts relative to another spot, then you could, just like you get electrostatic discharges at home when you walk across the carpet, you could get a discharge on the satellite, and that could cause an eruption in our activity. So we've taken great pains to engineer that out, by creating conductive surfaces all over the satellite that will equalize the, the voltages that build up. And just having the electronic boxes physically inside the spacecraft helps a lot, because you've got protective covering of all that metal on the outside.

Project Scientist Michael Kaiser and Deputy Project Manager Jim Adams, thanks for joining us on NASA Direct. (response)

Thank you very much and pay attention to the website, stereo.gsfc.nasa.gov, and look for our launch coming up later this summer. And the data that will ensue and change the way we look at the sun.

From the Kennedy Space Center in Florida, I'm George Diller.

This podcast was presented by NASA Direct.

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