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This article says why the lifetime of the Webb telescope is limited by the fuel it carries. Why NASA’s James Webb Space Telescope Will Never Live As Long As Hubble

In short, Webb must stay near the Earth and Moon for radio contact, while pointing away from the Sun, Earth, and Moon to stay cool. It can do this near the L2 Lagrange point while using very little fuel.

When it runs out of fuel, it will drift away. There will no longer be a single direction to the Sun, Earth, and Moon. At some point, there is no direction where all three are out of Webb's field of view.

When it does run out of fuel, I can imagine simplistic ways to rescue it. Of course it is never as easy as it sounds. But I am wondering what is wrong with these thoughts.

  1. Build a spacecraft whose sole purpose is to hold onto Webb's hot side and use its engine to position the pair. Granted, Webb wasn't designed to be held, but how hard can it be?

  2. When Webb runs out of fuel, it will drift away from the L2 point. It will still be able to run its reaction wheels and cryocooler from its solar panels. Keep it pointed away from the Sun. At some point, Earth will drift into the field of view of its cold side.

Send out a large sunshade which will stay between it and Earth, keeping it cool.

  1. Let Earth drift into the field of view. Webb will warm up. It will become insensitive to longer wavelengths. Perhaps it will not be able to see any of its design wavelengths.

Earth will drift away and Webb will cool down again.

One might help this idea out by using the last of its fuel to launch it away from the L2 point. By the time Earth drifted into view, Webb would be far from Earth.

  1. If we can stay in radio contact with Voyager, we can stay in radio contact with Webb even if it was on the opposite side of the Sun.
David Hammen
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    Would [space.se] be a better home for this question? – Qmechanic May 03 '22 at 06:32
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    These are too many too different questions for a single Q&A. And all of them have already been answered individually. – asdfex May 03 '22 at 10:09
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    Radio contact with Voyager is done with a very low data rate. To use the images of Webb, we need a much higher data rate. The Sun is not transparent for radio waves. – Uwe May 03 '22 at 10:43
  • I provided one of many questions as a duplicate. The multiple questions raised here have been asked and answered many times, in many forms. – David Hammen May 03 '22 at 12:02
  • Regarding "Granted, Webb wasn't designed to be held, but how hard can it be?" The answer is very hard. – David Hammen May 03 '22 at 12:02
  • Regarding "It will still be able to run its reaction wheels and cryocooler from its solar panels." No, it won't. Reaction wheels occasionally need to be desaturated. The loss of the ability to do so is how various space agencies have lost control of satellites. – David Hammen May 03 '22 at 12:05
  • Regarding "If we can stay in radio contact with Voyager, we can stay in radio contact with Webb even if it was on the opposite side of the Sun." The Voyager 1 data rate currently is 160 bits per second. There is no imagery at that slow rate. (All of the Voyager cameras were shut down long ago.) The goal of the Webb is to downlink 57.2 gigabytes per day. That amount of planned daily data would take almost a century to transmit at 160 bits per second. – David Hammen May 03 '22 at 12:11
  • Specifically, it would take 90.63 years at 160 bits/second (continuous) to transmit 57.2 gigabytes, so not quite a century. – David Hammen May 03 '22 at 12:18
  • One of the first things one learns as a spacecraft engineer is that one has to work with last gen -6 technology. The JWST flight computer is a RAD750, which is essentially a toned-down version of a very early Macintosh. (I call it a computer from the previous millennium.) It has a whopping 58.8 gigabytes of storage. Given that the launch was so precise that the JWST probably has enough fuel to last for 20 years, it might well be better to plan on replacing it rather than refueling it. – David Hammen May 03 '22 at 12:38

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