Convenience orekit-data switched back to tai-utc.dat

The convenience orekit-data repository that may be used to bootstrap an orekit-data folder provides some important data to users. This is only a convenience and not guaranteed to be either up-to-date or even maintained on the long time, but many people use it.

Some months ago (July 2021), we switched the leap second file provided in this repository from USNO tai-utc.dat to IERS UTC-TAI.history file as the USNO servers that were decommissioned.

However, according to IERS Message 450, the USNO maia server is back online. The tai-utc.dat file is therefore again available on a maintained server.

As the utc-tai.dat file is more user-friendly, and expected to be better maintained than UTC-TAI.history, we switched back the repository from UTC-TAI.history to utc-tai.dat. In past years, I had to ask at least on two different occasions to IERS to update the UTC-TAI.history file after some leap seconds were introduced.

This change should not affect most users. However, it is recommended to check your orekit-data folder and see if you have one or both files present. Only one file should be there, it is recommended to remove the other one, as otherwise you won’t know which file Orekit will parse (it knows how to parse both formats), and when the next leap second will be introduced, you may miss it if the file selected is not updated.