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With the launch of the JWST nearing, what happens in the worst case? Let's say the rocket explodes and everything is 100% lost.

Are there back-up copies? Is everything on it one-of-a-kind? Is there a duplicate sister telescope and a time table for launch?

I did see that NASA built an identical copy a "twin" of the Perseverance Rover.

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I want to clarify something about that "twin" of the Perseverance rover that you've mentioned, something that won't easily fit in a comment.

NASA built a twin of the rover not to have one as a backup rover in case the original rover explodes in transit or fails to land. They built one because they need a way to plan out movements in advance. Mars is so far away that it is impossible to directly control any device on the planet through manual control. It takes radio signals between 6 and 20 minutes to get to Mars, and it takes the return signals just as long to get back. So at best you have a 12 minute gap and worst you have a 45 minute gap between you sending the signals and you knowing the outcome of the command. So you need to be REALLY damn sure that you're sending the right commands, because there is no roadside assistance that can help you if you accidentally hit a rock or get stuck in a sand dune.

To that end, NASA uses the rover's twin here on Earth to meticulously prepare every command they send by first testing it with the twin, without the delay, on a recreation of the Mars rover's immediate area, including the shape and texture of rocks and the layout of the mars dirt they're driving on. Every command, from driving forward to sampling a rock to moving the camera to take a close-up picture is first tested in that simulated environment before sending it to Mars, similar to how a competent software developer tests their newly written software on a separate testing environment BEFORE they push their new code to a production environment.

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  • $\begingroup$ Fun fact: There is not a complete copy of the JWST here on the ground. $\endgroup$
    – Freddo411
    Dec 30, 2021 at 21:02
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There is no backup telescope.

There’s no room for error with the Webb, no backup telescope in a warehouse, and no chance of repairing it once it launches.

https://www.inverse.com/science/james-webb-new-delay

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  • $\begingroup$ What is the possibility of "WFIRST or Nancy Grace Roman telescope" taking JWST's job? Is it possible to modify it and to use it as backup? $\endgroup$ Dec 24, 2021 at 14:09
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    $\begingroup$ @SwiftPushkar Maybe, but building a completely new spacecraft with a different design is not what is meant by a "duplicate sister telescope". $\endgroup$ Dec 24, 2021 at 14:10
  • $\begingroup$ There was no chance of repairing Hubble when it launched. Which was lucky, because I made a lot of money fixing the images, until someone, uh, repaired it. Damn. $\endgroup$
    – EML
    Dec 26, 2021 at 12:02

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