James webb space telescope is very well known for its capabilities and at the same time it is also very well known for its delays. People have been waiting for its launch for nearly a decade now.
It's become something of a myth. It's been coming any-day-now for as long as anyone can remember.
It's certainly needed, since Hubble is ancient, sputtering and running on fumes. I just saw reports that it's shut down again due to some kind of computer problems. (Shut it off and turn it back on again, that's how I fix electronics.)
Finally it is on its way to get launched. It has now reached French Guiana.
It is to be launched by a French Ariane rocket. These have been experiencing problems of their own (with payload fairing deploy I believe), although the problems are said to have been rectified. They just launched two large communications satellites on the first Ariane after a lengthy standdown a couple of days ago and the launch was very successful. (I watched the Arianespace live-stream.)
We can be certain that the JWST people were watching that launch very closely.
I'm a little concerned about the JWST because it just looks fragile to me, the way that it unfolds itself like origami. And being a very large (6.5 meter) reflecting telescope, all of its parts have to end up very precisely aligned and situated. JWST costs billions and there's only one, so if it's lost or it fails, the whole project is done. The anxiety as it launches and deploys will be through the roof.
Now it is a good time to recall about its capabilities and the gains that NASA is going to make after it will be launched.
I believe that apart from improved optical resolution, it will have improved infrared performance, compared to Hubble. Astronomers are very interested in exploiting that. The infrared wavelengths that JWST will concentrate on are blocked by the Earth's atmosphere and Hubble isn't optimized to view them. But there are lots of interesting infrared objects out there, from accretion disks, to distant red stars (dwarves and giants), to distant high-redshift objects. Infrared might possibly make brown dwarves more visible. (I wonder if there are lots of these failed not-quite-stars out there between the stars whose luminosity we can see.
JWST will end up situated in an interesting spot as well, the Earth's L2 Lagrange point. JWST will be much further from the Earth than the Moon (about 930,000 miles from Earth) at a point in the opposite direction from the Sun on a straight line between the Earth and the Sun. Generally speaking, an object a million miles further from the Sun than the Earth will orbit the Sun more slowly than the Earth. But at the L2 point, the additional gravity of the Earth pulls the L2 object faster so that the point represents a stable station-keeping spot relative to the Earth and the Sun.
Why place the JWST way out there? Because the Earth and the Sun both occupy a fixed position in the sky relative to the telescope which can put out a parasol-like shield to block out both and not have to worry about constantly moving it. An infrared telescope is very sensitive to heat and both Earth and especially the Sun radiate heat. But at L2 the Sun is always on the opposite side of the Earth, so the Earth blocks the Sun and the parasol blocks the Earth and whatever solar infrared gets past Earth. It's a good spot for space telescopes that want to escape solar interference.
Here's an
11 year old page that explains the orbital mechanics stuff very well. (The age of the page indicates how long the JWST project has been brewing.)
https://www.nasa.gov/topics/universe/features/webb-l2.html
James Webb Space Telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency.
