# James Webb Space Telescope

Yes, it will be orbiting around L2. I don't think the orbit is perpendicular to the ecliptic, though. (I wonder if it's at the Earth's tilt angle...)

Hmm...

What's the Rotating Libration Point frame?

I thought it had to be perpendicular to take advantage of the gravity well around L2. As I understand it, any motion along the radius of the earth's orbit, i.e. along the extension of the line joining the sun and earth, will be unstable and cause it to move even further in that direction.
That makes sense. The effective gravitational potential around L2 is sort of saddle-shaped, as I understand it. So maybe the orbit is perpendicular to the ecliptic after all. I may well have misinterpreted a 2D projection of the 3D orbit in a video.

That makes sense. The effective gravitational potential around L2 is sort of saddle-shaped, as I understand it. So maybe the orbit is perpendicular to the ecliptic after all. I may well have misinterpreted a 2D projection of the 3D orbit in a video.
That's what I thought at first too.

However, the saddle is indeed a 2D representation, in the plane of the ecliptic. If you think in 3D, it seems to me the saddle becomes a 2D section through a doughnut-shaped ring of lower gravity. So the object tends to fall into the gravity well in the middle but also to slide out radially, down the flank of the doughnut, either in toward the earth or away from it. Hence the need for correction burns to the telescope from to time, once it is orbiting L2.

But I may still have got it a bit wrong.........

Hmm...

What's the Rotating Libration Point frame?
Objectively, the Earth/L system rotates 360 degrees around the sun over a year. As if we are standing on a record player, with the sun at the centre and we're standing on the surface of the rotating LP.

All this is saying is that - for clarity - the diagram's frame is within that rotation.

Nearly 2am 16th January 2022 Australia and I have nothing to better to do (like sleep) than the check on progress of James Webb telescope

Looks like about 85% there. Yah

Let's try sleep

However, the saddle is indeed a 2D representation, in the plane of the ecliptic. If you think in 3D, it seems to me the saddle becomes a 2D section through a doughnut-shaped ring of lower gravity. So the object tends to fall into the gravity well in the middle but also to slide out radially, down the flank of the doughnut, either in toward the earth or away from it. Hence the need for correction burns to the telescope from to time, once it is orbiting L2.
Useful information. That makes a lot of sense. Thanks.

Useful information. That makes a lot of sense. Thanks.
I've found a bit more on this. The orbit of the Webb telescope is evidently what is known as a "halo orbit": https://en.wikipedia.org/wiki/Halo_orbit. The diagrams shown in this article seem to be the same as those Dave posted in post 41.

This really is interesting stuff

I'm awe of the people who worked to put this sort of stuff together

I see the cruising speed is unchanged from yesterday at 0.1517ml/s.

Thought it might be slowing down
...

This really is interesting stuff

View attachment 4580

I'm awe of the people who worked to put this sort of stuff together

Think Lady Luck might have had a hand in it as well.

I see the cruising speed is unchanged from yesterday at 0.1517ml/s.

Thought it might be slowing down
...
Didn't notice that

Few distractions around

Update - just looked at couple of seconds ago now 1515 ya still slowing

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95% distance covered now.

Slowing down ,about 600 mph (.1477 ms/s) now I think I calculated.

95% distance covered now.

Slowing down ,about 600 mph (.1477 ms/s) now I think I calculated.
I made it 562 miles per hour, still a fair click

About 37 thousand miles to L2.

That is about the same as going around the equator and half the way around again.

They can almost see L2 now

Spinoff
The work performed on the telescope optics resulted in a NASA tech spinoff for diagnosing eye conditions and accurate mapping of the eye. This spinoff supports research in cataracts, keratoconus (an eye condition that causes reduced vision), and eye movement - and improvements in the LASIK procedure

From one of the James Webb Telescope articles about spin offs from the research which went into building the telescope

From research into building a artificial retina we get a spin-off to help diagnose problems in real retinas. NEAT

I made it 562 miles per hour, still a fair click
Down to 500, slower than your typical jet airliner at altitude.

Is the trajectory to L2 a bit complicated ?

I can see from the website that the distance to L2 has been actually be increasing over the past while.

Just over 34,000 miles now.

Is there something of a moving target here?

Unless the website is incorrect why has the distance to L2 been actually increasing over the past while?

Unless the website is incorrect why has the distance to L2 been actually increasing over the past while?
I don't know. I imagine that since it is going to orbit L2, and not end up at L2, that it is now moving into position to intercept that orbit.

However I looked at the "where is Webb" site and the distance listed to L2 orbit is now 33,900 miles and decreasing.