James Webb goes into Orbit around L2

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Graeme
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James Webb goes into Orbit around L2

Post by Graeme »

It's there!

https://blogs.nasa.gov/webb/2022/01/24/ ... ves-at-l2/

Can't wait to see what it can do.

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HansV
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Re: James Webb goes into Orbit around L2

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Should be fascinating!
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Jay Freedman
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Re: James Webb goes into Orbit around L2

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I'm trying to imagine what it takes to calculate JWST's center of mass, with the mirror and sunshields fully deployed, in order to place the engine in line with it to avoid making the whole thing tumble. :flee:

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Rudi
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Re: James Webb goes into Orbit around L2

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It's certainly a milestone event!!!
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ChrisGreaves
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Re: James Webb goes into Orbit around L2

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Jay Freedman wrote:
25 Jan 2022, 01:57
I'm trying to imagine what it takes to calculate JWST's center of mass, with the mirror and sunshields fully deployed, in order to place the engine in line with it to avoid making the whole thing tumble. :flee:
I would imagine that it is an equation based on "moment" of inertia. Back in my high school days this would involve something like identifying every one of thousands of parts - beams, plates, nuts, washers, bolts and so on, and determining (a) its mass (good laboratory scales) and its distance from some established point (our mathematics teacher Brian Feld would have us summon up our knowledge of Trigonometry and Calculus), and then just "doing the sums".

An impossible task, even for brilliant high school students such as I.

BUT: I escaped both high school and university and got into Computer Programming, in FORTRAN, Fortuitously :evilgrin:

Nowadays the JWT will be CAD/CAM or whatever it is.
Every part will be recorded in a database, probably right down to the temperature at the time it was weighed.
A little arithmetic function to calculate the mass/moment of inertia (section 8.1 page 22 of this document)
A little subroutine to add up the thousands of results.
And there you are!

Hope this helps
Chris

P.S. Knowing NASA they probably cheated and installed tiny jets to adjust the telescopes orientation in Real Time.
Assuming, of course, that it can "see" the stars.
C
Last edited by ChrisGreaves on 25 Jan 2022, 20:32, edited 1 time in total.
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BobH
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Re: James Webb goes into Orbit around L2

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Mr. Greaves, how long does it take a signal from it's L2 orbit to reach Earth?
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Jay Freedman
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Re: James Webb goes into Orbit around L2

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BobH wrote:
25 Jan 2022, 17:34
Mr. Greaves, how long does it take a signal from it's L2 orbit to reach Earth?
I'm not Mr Greaves, but... The distances to the L1 and L2 Lagrange points are approximately 0.01 times the distance from Earth to the Sun, or 1 475 000 km (http://www.phy6.org/stargaze/Slagrang.htm). Light and other radiation (signals) travel at 300 000 km/s, so it takes about 4.9 seconds. (Light from the Sun takes about 490 seconds, or 8 minutes, to reach Earth.)

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ChrisGreaves
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Re: James Webb goes into Orbit around L2

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BobH wrote:
25 Jan 2022, 17:34
Mr. Greaves, how long does it take a signal from it's L2 orbit to reach Earth?
Just a minute Bob; I'll get one of my staff to answer that.
Be patient; this could take up to five seconds. :clapping:
Cheers
Chris
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C
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Jay Freedman
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Re: James Webb goes into Orbit around L2

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ChrisGreaves wrote:
25 Jan 2022, 20:29
@Jay: Take the rest of the day off; you've earned it.
C
Thanks. I'm considering taking a vacation cruise to L1. I should be back in a few months. :grin:

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Re: James Webb goes into Orbit around L2

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I hope you'll find equilibrium there...
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Hans

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Graeme
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Re: James Webb goes into Orbit around L2

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ChrisGreaves wrote:
25 Jan 2022, 11:35
P.S. Knowing NASA they probably cheated and installed tiny jets to adjust the telescopes orientation in Real Time.
Assuming, of course, that it can "see" the stars.
C

Hydrazine fueled thrusters for keeping it in orbit around L2, smaller thrusters and reaction wheels for attitude control.

This might help:

https://jwst.nasa.gov/content/observatory/bus.html

The other pair of SCAT thrusters is mounted on a boom on the side of the spacecraft opposite the solar array, oriented such that their thrust direction passes through the deployed observatory's center of mass.

Not sure about the maths, but I'm looking forward to the images! :smile:

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Re: James Webb goes into Orbit around L2

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Graeme wrote:
26 Jan 2022, 07:23
...Not sure about the maths...
My eldest son tells the story of how, during his lectures at uni on the mind bending maths involved in rocket engineering, the lecturer was fond of saying, "i know this is hard but it's not rocket science. Oh, wait..."

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HansV
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Re: James Webb goes into Orbit around L2

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:laugh:
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Hans

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Jay Freedman
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Re: James Webb goes into Orbit around L2

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I see that NASA has a backup plan in case JWST runs into problems.
JWST Lego Set.jpg
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BobH
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Re: James Webb goes into Orbit around L2

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One wonders if Lego has been working on their version as long as NASA has. :scratch:
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