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posted by CoolHand on Monday June 20 2016, @09:42PM   Printer-friendly
from the better-than-our-pocket-telescope dept.

The James Webb Space Telescope (what could maybe be called a 'better Hubble telescope') is due to be launched in 2018.

Its primary mirror spans 6.5 metres, compared to Hubble's 2.5, giving it seven times more light-gathering power. It will also gather from the infrared spectrum instead of gathering visible light: this will allow it to 'see' past clouds of dust, to gather more information about the beginning of the universe.

It will NOT be fixable like the Hubble, though. It is going to be sitting out at L2 (Lagrange point 2 of the Earth-Sun system) which is 1,500,000 kilometers (930,000 mi) from Earth, directly opposite to the Sun. At this point, with the Earth, moon and sun behind it, the spacecraft can get a clear view of deep space.

Where exactly is L2 for the Earth-Sun system? You can work it out for yourself (https://en.wikipedia.org/wiki/Lagrangian_point#L2)

or look at pretty pictures
1. http://webbtelescope.org/webb_telescope/technology_at_the_extremes/graphics/fig-4-webb-orbit-big.jpg
2. http://www.stsci.edu/jwst/overview/design/orbit1.jpg

Why do you have to state 'L2 for the Earth-Sun system'?

[Continues...]

In celestial mechanics, the Lagrangian points (/ləˈɡrɑːndʒiən/; also Lagrange points, L-points, or libration points) are positions in an orbital configuration of two large bodies where a small object affected only by gravity can maintain a stable position relative to the two large bodies. The Lagrange points mark positions where the combined gravitational pull of the two large masses provides precisely the centripetal force required to orbit with them. There are five such points, labeled L1 to L5, all in the orbital plane of the two large bodies. The first three are on the line connecting the two large bodies and the last two, L4 and L5, each form an equilateral triangle with the two large bodies. The two latter points are stable, which implies that objects can orbit around them in a rotating coordinate system tied to the two large bodies.

ANY 3 body system will have 5 Lagrange points! (I did not know that).

http://www.cbc.ca/news/technology/james-webb-space-telescope-hubble-1.3557887


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  • (Score: 0) by Anonymous Coward on Tuesday June 21 2016, @12:11AM

    by Anonymous Coward on Tuesday June 21 2016, @12:11AM (#363097)

    That's a funny looking probe. It looks like a raft with a satellite dish on it. It even surpasses the Apollo lander, which looked like 4 pins stuck into a wad of foil. What's your candidate for funniest-looking spacecraft?

    On a more serious note, it's scary that it's not designed to be repaired, like Hubble is. Then again, most spacecraft aren't. Hubble was lucky in that regard, especially since they fouled up the original optics. Cross your rafts, I mean fingers.

  • (Score: 0) by Anonymous Coward on Tuesday June 21 2016, @11:32PM

    by Anonymous Coward on Tuesday June 21 2016, @11:32PM (#363592)

    it was designed as such since it will be located at a distance too far for manned crews to reach

    unless we get our shit together and have manned capability beyond LEO then we'll have to settle with robust sattelites