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What is the furthest from the Earth that still offers a total eclipse of the Sun? Is L2 inside that distance? (I assume so due the the halo orbit that is planned but perhaps there are numerous other reasons to fly around the L2 Lagrange point)

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No.

The Earth's umbra extends 1.4 million km. The L2 point is at 1.5 million km. Even if perfectly aligned, the Earth will only show as an annular eclipse, shading about 70% of the sun's disk.

However, the halo orbit of JWST will never pass through this region, nor even near it. The operational requirements demand that the telescope never pass through any part of the Earth or Moon shadow.

Additionally, the rather large Halo orbit is chosen to maximize stability, specifically to minimize thruster fuel usage required to keep the probe in the orbit, as discussed here: https://space.stackexchange.com/questions/15167/are-large-halo-orbits-around-l₁s-and-l₂s-preferred-over-small-orbits-for-reaso.

JWST orbit illustrated, the circle is not the Earth, it is the Moon's orbit. enter image description here

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    $\begingroup$ 10355/what-does-the-sun-earth-moon-system-look-like-from-the-sun-earth-l-2-point?rq=1 Has some more graphics and calculations. $\endgroup$
    – user277093
    Dec 26, 2021 at 8:18
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    $\begingroup$ > The operational requirements demand that the telescope never pass through any part of the Earth or Moon shadow. why? Is this to guarantee the JWST solar power arrays are drawing full solar power? $\endgroup$
    – Sheldon
    Dec 26, 2021 at 13:41
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    $\begingroup$ @Sheldon space.stackexchange.com/questions/56047/… $\endgroup$ Dec 26, 2021 at 13:43

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