Using skyfield I get the error :

OSError: cannot get ftp://cddis.nasa.gov/products/iers/deltat.data because <urlopen error ftp error: TimeoutError(10060, 'Ein Verbindungsversuch ist fehlgeschlagen, da die Gegenstelle nach einer bestimmten Zeitspanne nicht richtig reagiert hat, oder die hergestellte Verbindung war fehlerhaft, da der verbundene Host nicht reagiert hat', None, 10060, None)>

I found this message:

US Government security requirements no longer permit CDDIS to offer data via traditional unencrypted anonumous ftp; this service was discontinued on October 31, 2020. All data are still available, however access must be via HTTPS or ftp-ssl.

So how to use HTTPS instead of FTP?

Should I install PycURL – A Python Interface To The cURL library?

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    $\begingroup$ I’m voting to close this because it's a coding question, not space exploration. Stack Exchange itself would be a better place to ask this. $\endgroup$
    – GdD
    Nov 17, 2020 at 17:51
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    $\begingroup$ Surely this is a question about how to use an app, not how to code it. $\endgroup$ Nov 17, 2020 at 18:09
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    $\begingroup$ @OrganicMarble The issue seems to be that Skyfield uses an internal FTP connection to CDDIS to update it's internal Earth orientation data. That update method is no longer working due to US government mandated changes to improve server security (I suspect this is also what has lead to the extended downtime of the USNO servers and rewrite of several pieces of code that used to hit USNO for the info, to get the needed data from elsewhere) $\endgroup$ Nov 17, 2020 at 18:18
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    $\begingroup$ Agree that the question could have been borderline for this site but it seemed a simple fix and wanted to spare the OP from having to go to Stack Exchange - there be dragons... ;-) $\endgroup$ Nov 17, 2020 at 18:22
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    $\begingroup$ @JCRM For issues such as "I'm doing it like the documentation says but now I'm getting this strange error" Skyfield's Github Issues might be the first point of call. But this particular issue involving NASA servers it's fine here and in fact kind of interesting! 80 views in 21 hours, 9 total up votes... it's benefits the site to ask here. $\endgroup$
    – uhoh
    Nov 18, 2020 at 15:30

2 Answers 2


Looks like this was an issue that was fixed and closed recently so try updating your copy of Skyfield to at least version 1.31.

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    $\begingroup$ Yes, upgrading skyfield to 1.31 should help. I will try. $\endgroup$
    – Uwe
    Nov 17, 2020 at 18:16
  • $\begingroup$ After upgrading to 1.31 I had to add the line: conf.iers_auto_url = 'toshi.nofs.navy.mil/ser7/finals2000A.all' But this was not all, I had to download the file 'finals2000A.all' into the directory ...Documents/fishing/SkyData\\finals2000A.all' manually $\endgroup$
    – Uwe
    Nov 18, 2020 at 9:24
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    $\begingroup$ This seems to be a bug in skyfield and I suggest you file an issue there. According to the docs you should be able to do a from skyfield.api import load ; load.timescale(builtin=False) but this fails for me also. The code in iokit.py has the URL for the finals2000A.all but just tries to open a local copy and doesn't fetch it if missing. $\endgroup$ Nov 18, 2020 at 17:21
  • $\begingroup$ Yes, I think so, it seems to be a bug and I will file an issue. But I have to register first. I agree, if the local file is missing, it should be fetched anyway. $\endgroup$
    – Uwe
    Nov 18, 2020 at 17:59
  • $\begingroup$ I filed an issue and got help. I upgraded to 1.33 as recommended and renamed the local file finals2000A.all to another name. The file was loaded again without problems into the directory ..\Documents\fishing\SkyData Problem solved in version 1.33 $\endgroup$
    – Uwe
    Nov 18, 2020 at 21:57

For those who found this question because they wanted the IERS data, from one of the main sources of space data in the world, here are the lower-level details about how to get deltat.data etc. They are still updating the files, but now require a more modern file transfer protocol (e.g. https) and a login, which is free to anyone. The changes are explained here:

CDDIS | | Data and Derived Products | CDDIS Archive Access

That explains getting a login and configuring various tools like curl, wget, python etc. I found that I had to use the server name urs.earthdata.nasa.gov in the .netrc file to get curl to find my credentials and log me in automatically. Then I could just run e.g.

curl -c cookiefile -n -L "https://cddis.nasa.gov/archive/products/iers/deltat.data"

It was a bit confusing to finding the new URLs for the IERS files on the NASA servers. I found the data in the directory at


e.g. https://cddis.nasa.gov/archive/products/iers/deltat.data

In the readme they say that they update deltat.data every quarter or so, though it is now nearly a year out-of-date. But the finals.daily.extended file seems comprehensive and up-to-date.

Most of the same data (but not deltat.data) is also available without a login, via https or ftp, direct from IERS - Earth orientation data


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