Here's documentation on independent backup efforts of various government websites: https://www.reddit.com/r/DataHoarder/comments/1ifalwe/us_gov...
Also here: https://www.reddit.com/r/DataHoarder/comments/1idj6dm/all_us...
Apparently, much of the data has been back up here: https://eotarchive.org/
Here's also a discussion on whether the Internet Archive is sufficiently backed up/decentralized (it is not): https://www.reddit.com/r/DataHoarder/comments/1if32iq/does_i...