Change the Sts unpacker par to match the mcbm21 geometry

Change the Sts unpacker par to match the mcbm21 geometry

assigned to @p.-a.loizeau

requested review from @p.-a.loizeau

Dear @f.uhlig, @p.-a.loizeau,

you have been identified as code owner of at least one file which was changed with this merge request.

Please check the changes and approve them or request changes.

added CodeOwners label

merged