Some of them just head out and will forever roam away from their planet of birth, like Voyagers 1 and 2 and Pioneer 10. Some stay a little closer but also travel unspeakable distances. Lots of them pass Earth more than one time again to gain speed to catapult themselves into another orbit or trajectory to a planet, comet or some other celestial body.
Special ones are designated to spend their working life at the poetically named Lagrange points. These specific spots in the neighbourhood of a planet or moon are exactly where the gravitational pull is more or less cancelled. An object placed at such a point will travel around the sun with the same speed as the Earth and moon and will look stationary from the viewpoint of as well the Earth as the moon. Such points are ideal for stationing or observation.
|Lagrange points around the Earth and its Moon.|
Planck is such a space telescope. It was built by the European Space Agency to be placed there and survey the galaxy around us.
In 2009 Planck was launched, together with its brother telescope, Herschel, on top of an Ariane 5 from Kourou. Planck was placed at the L2 point and there observed the phenomenons of the universe, mainly things like the cosmic background noise which is used to determine the age of the universe. Planck was operational until august 2013. After that, it had run out of cooling fluid for its telescope parts and it could no longer function. It then was put into a parking orbit around the sun, to keep the L2 point free for successors and was powered down.
Well, that's just a little tip of the iceberg. Lots more to tell about Planck. But I started with a model of the telescope. And that is what this blog is about. Paper models.
Here's where it started, more after the jump.
*"practically always in the shadow of the moon": of course this is only partially true. In reality, the probe orbits in a special "wobbly orbit" around the imaginary Lagrange point, so it also can catch some sunlight to power its equipment.