The geodetic information used by CASA is updated regularly using the TAI_UTC table in the CASA data repository, which is derived from measurements provided by the Earth Rotation and Reference Systems Service (IERS). A slightly outdated table is not likely to be a problem since most data is averaged over sufficiently long time intervals. However, it could be a problem for VLBI observations.The update can be run from the CASA command prompt using
$ casa-config --exec update-data
Attention: In late 2015, the CASA data repository moved to a new server. This resulted in an rsync error when updating the repository in CASA 4.4 or earlier. To fix this problem, a patch script can be run outside CASA.
$ update-data.patch <PATH-TO-CASA-DISTRIBUTION>
<PATH-TO-CASA-DISTRIBUTION> is the path to the top level of the unpacked CASA distribution.
More information is available in the Fixing out of date TAI UTC tables CASA Guide.