csspckgen

This program creates the latest PCK SPICE DB file for the Cassini missions. The Cassini mission continually refines its approximations of planetary constants, and so regularly releases their latest PCK with each SPK release. There are only two PCKs that need to be considered: a general Cassini PCK and a Jupiter PCK. Each file is versioned with a date string.

New version of Isis are capable of resolving this date string and grabbing the latest PCK from the data area. In an effort to support legacy versions of Isis 3, this program adds Selection groups for the direct paths to the latest PCK files, and is called by the makedb script within the Cassini PCK directory in order to always contain the latest PCKs.

When initializing a file, spiceinit will grab the last PCK in the DB file that it can use for the given coverage period. With this in mind, the date-versioned filenames should be placed below the direct filenames such that new versions of Isis will resolve the latest PCK at runtime. This way, in case a user is missing the directly specified PCK, they could fall back to whatever happens to be the latest PCK in their data area. Unfortunately, in legacy versions of Isis 3, spiceinit only looks at the coverage time, and does not consider whether a file exists when determining if it is usable, thus the date-versioned filenames must be placed above the direct filenames, and will thus not be used until legacy support is dropped.

Once all supported versions of Isis contain the date-versioning logic, these direct filenames should no longer be added by this program, and removed from all future DB files.