... SPICE Required Reading Documents . cells - Reference for the SPICE cell data structure, which is a vector of type double precision, integer or character type that carries with it its own dimension and knowledge of how many components have been used. ? ck - Reference for the SPICE orientation subsystem and C-Kernel (CK), used to provide the orientation (a.k.a. attitude) of a spacecraft or an articulating component of a spacecraft or instrument. ? ...