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in 2006 nasa launched the solar

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terrestrial relations observatory or

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stereo spacecraft

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over the last four years the two

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spacecraft have slowly made their way

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along earth's orbit with stereo a

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advancing ahead and stereo b falling

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behind

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as they've separated our view of the sun

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has increased

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other satellites near earth such as soho

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and now sdo continue to watch the sun

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from earth's perspective while the

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stereo spacecraft see increasingly

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different views

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now stereo a and b are almost exactly

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opposite each other and for the first

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time in human history we have a view of

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the sun has a huge influence on everyday

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life and with our increased reliance on

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technology this influence just keeps

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getting stronger

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coronal mass ejections and solar flares

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are the hurricanes of space weather and

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they have the power to disrupt our

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navigation systems communications and

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even electrical grids so it's vital we

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know when they are coming

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just as protecting our homes requires

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the best possible weather forecast

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protecting these systems requires the

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best possible space weather forecast

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sunspots and other active regions on the

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sun can help predict a new round of such

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space weather but before stereo we were

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able to see only one side of the sun at

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a time

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we couldn't tell what was starting to

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form on the far side

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since the sun takes about 27 days to

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rotate once solar activity had plenty of

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time to build unnoticed

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scientists first began to get a sense of

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the far side with soho's michelson

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doppler imager which worked almost like

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an ultrasound to give a view of the

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sun's back based on observations of the

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ripples on its front

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now stereo can make direct observations

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and eliminate any uncertainty about

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activity on the far side of the sun

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this unprecedented view will last for at

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least another eight years as the

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spacecraft slowly continue their journey

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they will cross behind the sun and then

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once again continue to opposite sides of

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the sun this time with their positions

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reversed

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during that time astronomers will be

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able to see magnetic active regions

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wherever they form on the sun so we will

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know about regions on the far side well

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before any earth-based observatory can

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the full view of the sun from stereo and

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sdo coupled with the other spacecraft in

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nasa's heliophysics fleet will help

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scientists understand our dynamic star