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(music throughout)

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So to steer a spacecraft from

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millions of miles away,
we have to first track its trajectory.

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So we have to determine where
in the Solar System the spacecraft is,

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predict where it's heading, and compare
that to where we want it to go.

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So the navigation team ensures
Lucy's on the right trajectory by tracking

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Lucy's position and velocity in the solar
system, predicting where it's headed

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and adjusting its course
so that it aces the flyby.

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So once Lucy starts approaching
one of its asteroid targets,

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the navigation team utilizes
the instruments, the cameras on board

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to take pictures of the asteroid
and background stars.

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And that helps us hone in on targeting
this close flyby.

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So commands travel at the speed of light.

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And over the course of Lucy's

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trajectory, its position
from Earth is varying substantially.

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When Lucy is near
Earth, during our earth, gravity assists.

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It takes a mere seconds for the data
or commands to be received

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by the spacecraft and for the spacecraft
to send data back to us.

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But at the farthest
extent of Lucy's trajectory

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and the farthest distance from Earth,
it can take up to an hour for our commands

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to be received traveling
at the speed of light.

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It's not only the data

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encoded in the signals, but
it's the properties of the signal itself.

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We know what time the spacecraft

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sent the data and we know what time
it was received on Earth.

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So we can calculate how long it took the
signal to travel at the speed of light.

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And that gives us information
about how far Lucy is from Earth.

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And then we also can get velocity
information because the spacecraft

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is moving away from the Earth
as it's sending those signals.

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And so there's a change in the frequency
of this radio signal.

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And that gives us
information about velocity.

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So like all NASA missions,
Lucy is designed to be robust to anomalies

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or surprises. But in the event
that something unexpected happens,

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there's either a contingency
plan on the shelf or a group of relevant

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mission experts are brought in to come up
with the best solution

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to solve the problem.