What is a SPICE-style Accumulating Data Set?

SPICE data sets are of the "accumulating" nature, meaning that after an initial delivery, as the mission progresses, NAIF adds to the data set at regular intervals, such as every three months or every six months, according to the mission's archive plan. In such cases the PDS data set ID, including the version number component, remains the same throughout the accumulation process; the data set simply contains more data with each increment.

Even after the mission is complete a SPICE data set retains its "accumulating" status. If additional or improved data are added months or years after the mission is over, the version number remains fixed at "v1.0." This is appropriate because kernel formats and labels are not changed, and superseded kernels are not removed. If meta-kernels (also known as "furnsh kernels") are included in the data set, as is the usual case, a new meta-kernel(s) that includes the new kernel(s) is added to the meta-kernel collection.

The time span currently covered by the archive is shown on the web page listing these data sets. The "stop time" is typically six or even many months earlier that today's date.