IGS is adopting a new coordinate frame (IGS20) and file naming scheme as seen in this announcement: https://igs.org/news/igs20/.
As part of this change they are modifying the file naming scheme used for the GPS SP3 files (http://acc.igs.org/repro3/Long_Product_Filenames_v1.0.pdf). The GPS week and day of week in the file name have been replaced by UTC year and day of year.
Example previous Rapid name:
Example new Rapid name:
Example previous Ultrarapid name:
Example new Ultrarapid name:
The project I am working on saw a negligible difference in the results with the change in the coordinate frame. For GPS weeks 2222-2237, you can use data in https://cddis.nasa.gov/archive/gnss/products/WWWW/igs20/ (where WWWW is the GPS week) to compare the IGS20 coordinate frame data with the previous system.
CDDIS might need to update this page to reflect the new naming scheme:
The IGS0OPSULT_20223310600_02D_15M_ORB.SP3.gz should actually translate to igu22381_06.sp3.Z. The reason for this is that the new file naming scheme includes a start date and the time span (two days). The old file naming scheme used the file center point in the filename instead of the start so the date in the old file names is one day after the new files.
I am unfamiliar with the GAMIT GLOBK software to be able to shosseini's question.