Recently, after over 9 years of travel through the Solar System, New Horizons arrived at Pluto and flew through the system. I've talked about the probe before and you can click the link above to see my previous post. New Horizons has already taken some amazing images of the system, and we will be getting more images as time goes on.
However, the amazing feat is not that we are taking images of Pluto and its moons, but that New Horizons actually made it to Pluto. Many things could have gone wrong: it could have been hit by an unknown asteroid or comet, it could have inexplicitly lost power, or a biggie: the trajectory could have been miscalculated.
When we go to any body in the solar system, we cannot aim directly for it. Much like a quarterback leads his receiver in American football, the probe must be aimed ahead of the planet or body and must arrive at the same place and time as the planet or body.
In the image down below, if we were to aim a spacecraft at Mars where it is now located, by the time we reached it, Mars would be farther ahead in its orbit. To reach Mars, we must aim to where Mars will be in about six months (the minimum time it takes to reach Mars from Earth). For longer travel times, we must aim farther ahead in the Martian orbit.
To reach Pluto took a little more doing. We had to know how long it would
take to reach Pluto, and aim New Horizons to where it will be then. Knowing
that New Horizons will reach the Pluto system in nine years and how fast Pluto
is moving on its orbit, engineers and scientists were able to determine where
New Horizons should be aimed towards in nine years. They also had to worry
about avoiding the other planets and moons, and had to hope that New Horizons
wouldn't encounter any stray asteroids or comets that we did not know about.
The Earth is in relatively the same
location on its orbit as it was nine years ago.
