IERS-A data emitted IERSDegradedAccuracyWarning in astropy 5.3.3 but throws ValueError in astropy 7 or later #19823

Activity

1. pllim

   added

   Bug

   utils.iers

   on May 28, 2026
2. RadeshL commented on May 31, 2026

   

   RadeshL

   on May 31, 2026

   More actions

   hey! I would love to contribute to this issue.

   going through the issue, at first I thought that, I might need to write a new test file to verify this issue. However on running the astropy/utils/iers/tests/test_iers.py file I got this output, which pinpoints to the issue currently being faced. Heres the screenshot of it:

   

   I ran it with this command :
   python -m pytest astropy/utils/iers/tests/test_iers.py -k test_iers_download_error_handling --remote-data -v

   this is the code in the test_iers.py file that handles the iers_degraded_accuracy:

   iers.conf.set_temp("iers_degraded_accuracy", "ignore"):
               (now + 400 * u.day).ut1

   So it is clear that, even after setting it to "ignore", the test throws out a value error.

   Here is what I did to solve this issue:

   in the astropy/utils/iers/iers.py file I've added code for configuration handling before raising an exception. Heres the code of the implemented block:

   if conf.iers_degraded_accuracy == "error":
                   raise ValueError(INTERPOLATE_ERROR.format(auto_max_age))
   elif conf.iers_degraded_accuracy == "ignore":
                   pass

   While looking through the file, I also noticed that there is another configuration supported named "warn" in the astropy/utils/iers/iers.py file :

   iers_degraded_accuracy = _config.ConfigItem(
           ["error", "warn", "ignore"],
           "IERS behavior if the range of available IERS data does not "
           "cover the times when converting time scales, potentially leading "
           "to degraded accuracy.  Applies also when using cached IERS-A data.",
       )

   I am not sure as to how do you want to display the warning message, is this the right way to do it:

         warn(
                       INTERPOLATE_ERROR.format(auto_max_age),
                       IERSDegradedAccuracyWarning,
                   )

   After the changes made in the code, there is no value error being thrown. This is the output of test:

   

   
   
   
   

   I also want to higligh that this failure was present both before and after my changes, so it seems unrelated to the iers_degraded_accuracy issue and may be outside the scope of this PR.

   

   
   
   
   Could you please confirm whether the proposed handling for the "warn" configuration is right?
3. mhvk

   added a commit that references this issue on Aug 23, 2026

   Apply iers_degraded_accuracy to stale IERS_Auto predictive values (#2…

   ...

   9f4de8d
4. mhvk

   closed this as completedin #20256on Aug 23, 2026