Thread by @NASAWebb

So…you’ve heard that the Webb telescope will be orbiting Lagrange point 2. But what even is that, anyway? And how do you orbit something that isn’t an object?

We’ve got you! Here’s a thread ⬇️
#UnfoldTheUniverse

First, the basics. Lagrange points refer to locations where the gravitational forces of 2 massive objects — such as the Sun and Earth — are in equilibrium. Webb will be located more specifically at Sun-Earth Lagrange point 2, or L2 for short.

Why send Webb to orbit L2?

😎 Shade: The Sun, Earth (and Moon) are always on one side. At L2, Webb’s sunshield can always face all of these heat & light sources to protect Webb’s optics & instruments, which have to stay super cold to detect faint heat signals in the universe.

👀 Views: Webb can access nearly half the sky at any given moment, and the entire sky over the course of 6 months.

Watch this video to learn more:

⛽️ Efficiency: Many of you have asked: Why doesn’t Webb just sit at L2? It’s actually simpler & more efficient for Webb to orbit L2!

⚡️ Power: This orbit also ensures that Webb will never have the Sun eclipsed by Earth — necessary for Webb’s thermal stability & power generation.

📞 Communication: L2 is convenient for always maintaining contact with our Mission Operations Center at @SpaceTelescope through the Deep Space Network. Webb isn’t the first spacecraft to orbit L2, either! Other observatories like WMAP & Herschel also orbit L2 for these reasons.

As Webb approaches L2, you may have noticed on webb.nasa.gov/whereiswebb that we're slowing down. Here's why:

Think about throwing a ball straight up in the air. It starts out very fast, but slows down as gravity pulls it down...

Similarly, Webb’s @Ariane5 rocket gave it energy to go a great distance, but not enough to escape Earth’s gravity. Just like the ball, Webb slows down & would eventually fall back towards Earth if we let it.

If the @Arianespace rocket had given Webb more energy than it had, Webb would have been going too fast when it got to L2, and we would overshoot our desired orbit. Webb can’t brake or turn back, as it would both cost a lot of fuel and require Webb to expose its optics to the Sun.

🚀 Webb's rocket gave it juuuust enough energy to be placed into its orbit — with a few course-correction burns along the way to make up the difference. Rocket engines aboard Webb will use thrust about every 3 weeks to keep it looping around L2 in a halo orbit every 6 months.

💫 Want to know even more about our orbit? Read our latest blog post: blogs.nasa.gov/webb/2022/01/2…

Or check out our orbit webpage: jwst.nasa.gov/content/about/…
#UnfoldTheUniverse