(music throughout)
So to steer a spacecraft from
millions of miles away, we have to first track its trajectory.
So we have to determine where in the Solar System the spacecraft is,
predict where it's heading, and compare that to where we want it to go.
So the navigation team ensures Lucy's on the right trajectory by tracking
Lucy's position and velocity in the solar system, predicting where it's headed
and adjusting its course so that it aces the flyby.
So once Lucy starts approaching one of its asteroid targets,
the navigation team utilizes the instruments, the cameras on board
to take pictures of the asteroid and background stars.
And that helps us hone in on targeting this close flyby.
So commands travel at the speed of light.
And over the course of Lucy's
trajectory, its position from Earth is varying substantially.
When Lucy is near Earth, during our earth, gravity assists.
It takes a mere seconds for the data or commands to be received
by the spacecraft and for the spacecraft to send data back to us.
But at the farthest extent of Lucy's trajectory
and the farthest distance from Earth, it can take up to an hour for our commands
to be received traveling at the speed of light.
It's not only the data
encoded in the signals, but it's the properties of the signal itself.
We know what time the spacecraft
sent the data and we know what time it was received on Earth.
So we can calculate how long it took the signal to travel at the speed of light.
And that gives us information about how far Lucy is from Earth.
And then we also can get velocity information because the spacecraft
is moving away from the Earth as it's sending those signals.
And so there's a change in the frequency of this radio signal.
And that gives us information about velocity.
So like all NASA missions, Lucy is designed to be robust to anomalies
or surprises. But in the event that something unexpected happens,
there's either a contingency plan on the shelf or a group of relevant
mission experts are brought in to come up with the best solution
to solve the problem.