The default value for the Unit attribute for each system is shown in parentheses. Strictly, these systems should not allow changes to be made to the units. For instance, the usual definition of "MJD" and "JD" include the statement that the values will be in units of days. However, AST does allow the use of other units with all the above supported systems (except BEPOCH), on the understanding that conversion to the "correct" units involves nothing more than a simple scaling (1 yr = 365.25 d, 1 d = 24 h, 1 h = 60 min, 1 min = 60 s). Besselian epoch values are defined in terms of tropical years of 365.2422 days, rather than the usual Julian year of 365.25 days. Therefore, to avoid any confusion, the Unit attribute is automatically cleared to "yr" when a System value of BEPOCH System is selected, and an error is reported if any attempt is subsequently made to change the Unit attribute.
KAPPA --- Kernel Application Package