The arrival marks the end of a bizarre 1.5 million kilometer journey across the universe and the beginning of a beautiful mission in search of the origin of the universe.

Just a little while and then the long-awaited James Webb telescope can really get to work. The space telescope will arrive at its final destination later today: a place about 1.5 million kilometers from Earth.

Lagrangian point 2

James Webb will settle in a spot near the so-called second Lagrange point. Draw an imaginary line from the sun to the earth, extend the line just 1.5 million kilometers longer and you are at L2: the point from which the telescope must unravel the secrets of the cosmos.

Reasons

The telescope will operate from a loose orbit – many hundreds of thousands of kilometers in diameter – around L2. It is no coincidence that this place was chosen. The great advantage of this position is that an object in L2 always maintains the same position relative to the sun and the earth. This makes communication and calibration with the space telescope easier. For example, continuous contact with the Deep Space Network – a collection of powerful radio antennas mainly used to communicate with spacecraft operating beyond the moon – will be possible continuously.

The second Lagrange point. Image: NASA

In addition, James Webb is bathed in constant sunlight near L2, which allows him to generate enough power through his solar panels. Moreover, as seen from the sun, this place is directly ‘behind’ the earth. The telescope’s orbit ensures that it stays out of the shadows of both the Earth and the Moon and has a virtually unobstructed view of the night sky. Observations can therefore continue around the clock. L2 is thus an ideal location for astronomical observations for several reasons. Several missions have already observed the universe from this location, including the satellite Wilkinson Microwave Anisotropy Probe (WMAP), radio telescope Planck Observatory and space telescope Herschel.

course corrections

To get to this spot, the James Webb telescope has already made two crucial course corrections. The first — and the most important — the James Webb telescope was running quite shortly, about 12 hours after its launch. Sixty hours after launch, maneuver number two followed. This course correction lasted only 9 minutes and 27 seconds, but thanks to this brief maneuver, the telescope refined its path to L2. As James Webb nears his final destination, the final course correction follows. James Webb will turn on his thrusters again momentarily. This third ‘burn’ is needed to place the telescope in L2.

Bizarre trip

When James Webb arrives at his destination today, he will have a bizarre and exciting journey. When the space telescope was launched on Christmas Day, it folded like an origami to fit inside an Ariane-5 rocket. And as it hurtled through the vast universe, it unfolded more and more parts effortlessly. A great achievement. As many as 344 things could go wrong from launch to end of the mission, the James Webb mission team said before the mission. But James Webb has unfolded all his parts neatly and according to plan.

First images
The first images of James Webb are still a while yet. After James Webb arrives at the destination, it takes engineers about five months to calibrate the instruments and align the mirror segments so that they function together as one large mirror. That time is also necessary to allow the telescope to cool down further; the telescope must be very cold to observe the infrared light from faint, distant objects. The first observations are therefore not expected until the end of June.

But from then on, Webb will explore every phase of cosmic history—from within the solar system to the most distant observable galaxies in the early universe, and everything in between. Webb will reveal new and unexpected discoveries and help humanity understand the origin of the universe and our place in it.