WEBVTT FILE

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tone

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Hi, folks, I'm Joe Gurman, the STEREO project scientist

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at NASA's Goddard Space Flight in Greenbelt, MD.

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STEREO, or the Solar Terrestrial Relations Observatory,

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is a NASA mission consisting of 2 spacecraft, orbiting the sun in orbits just

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inside and outside the Earth, with the objective of learning more

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about solar activity and how it propagates through the heliosphere.

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Today, we are talking about what is going with the STEREO mission.

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over the next year and a half or so, that includes both a period of superior

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conjunction, when the spacecraft on the other side of the sun from the Earth,

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and also a longer period on the other side of that, when the Earth

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the high gain antennae will have to off-pointed for once

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opting toward the Earth because of a thermal problem.

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During those weeks of superior conjunction for each spacecraft, the noise level

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of getting their signals back will be too high, simply because

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the antennae here on Earth will be looking at the sun as well as the spacecraft.

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During that period, we won't be able to communicate with the spacecraft,

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and after about 3 days, there's a timer on the spacecraft that will go off

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and put it in safe mode. It will also turn off the power

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to the instruments. And that's a period of about 15 weeks on the ahead spacecraft

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and 9 weeks on the behind spacecraft. Fortunately,

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those periods don't overlap. In August 2014,

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we will reach a situation where the high gain antennae on the STEREO spacecraft

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will be pointing back toward Earth, but seeing too much of the sun.

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That means that the feed of the focus of that antennae will be getting too

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hot, and we will have to start off-pointing the antennae, and using the weaker

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so-called side lobes to communicate with the Earth. That means we can't

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get back as much data in the given amount of time as we could before.

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We are going to be carefully cherry-picking the which data we send back

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during that period. That's a period of about 16 months on the ahead spacecraft

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and 14 months on the behind spacecraft, and it will take us

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to approximately the beginning of 2016 when we can resume

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normal operations on the main lobe of the antennae. During those periods of

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time, we will be down to about 7.4 kilobits a second

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and 1.7 kilobits a second science telemetry.

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It's worth noting that even the smaller of the 2 numbers is a

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factor of 10 greater than the rate we currently get back from Voyager 2,

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which is at the outer limits of the solar system. Those data are certainly

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worth taking, and we believe the data from STEREO are worth taking too

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as STEREO gives us the only view of what's going at the far side of the sun

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and in the heliosphere on that side as well.

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beeping

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beeping