rms-textkernel 1.0.1

Routines for parsing SPICE text kernels

PyPI Release	Test Status	Code Coverage

rms-textkernel

Supported versions: Python >= 3.8

PDS Ring-Moon Systems Node, SETI Institute

TextKernel Library

This is a set of routines for parsing SPICE text kernels. The simplest use case is as follows:

        import textkernel
        tkdict = textkernel.from_file('path/to/kernel/file')

The returned dictionary is keyed by all the parameter names (on the left side of an equal sign) in the text kernel, and each associated dictionary value is that found on the right side. Values are Python ints, floats, strings, datetime objects, or lists of one or more of these.

This module implements the complete syntax specification as discussed in the SPICE Kernel Required Reading document, "kernel.req": https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/kernel.html

For convenience, the returned dictionary adds additional, "hierarchical" keys that provide alternative access to the same values. Hierarchical keys are substrings from the original parameter name, which return a sub-dictionary keyed by part or all of the remainder of that parameter name.

Parameter names with a slash are split apart as if they represented components of a file directory tree, so these are equivalent:

        tkdict["DELTET/EB"] == tkdict["DELTET"]["EB"]

When a body or frame ID is embedded inside a parameter name, it is extracted, converted to integer, and used as a piece of the hierarchy, making these equivalent:

        tkdict["BODY399_POLE_RA"] == tkdict["BODY"][399]["POLE_RA"]
        tkdict["SCLK01_MODULI_32"] == tkdict["SCLK"][-32]["01_MODULI"]

Leading and trailing underscores before and after the embedded numeric ID are stripped from the hierarchical keys, as you can see in the examples above. Note also that the components of the parameter name are re-ordered in the second example, so that the second key is always the numeric ID.

When the name associated with a body or frame ID is known, that name can be used in the place of the integer ID:

        tkdict["BODY"][399] == tkdict["BODY"]["EARTH"]
        tkdict["FRAME"][10013] == tkdict["FRAME"]["IAU_EARTH"]
        tkdict["SCLK"][-32] == tkdict["SCLK"]["VOYAGER 2"]

If a frame is uniquely or primarily associated with a particular central body, that body's ID can also be used in place of the frame's ID:

        tkdict["FRAME"][399] == tkdict["FRAME"]["IAU_EARTH"]

Note that the "BODY" and "FRAME" dictionaries also have an additional entry keyed by "ID", which returns the associated integer ID:

        tkdict["FRAME"][623]["ID"] = 623
        tkdict["FRAME"]["IAU_SUTTUNGR"]["ID"] = 623

This ensures that you can look up a body or frame by name and readily obtain its ID.