| Edition | Keyword Add-on | Best For | | :--- | :--- | :--- | | | "Explanatory Supplement 1961 archive" | Historical research, understanding old ephemerides, pre-space-age astronomy. | | 1992 | "Explanatory Supplement 1992 P. Kenneth Seidelmann" | The standard for 90s astrometry; still used in legacy aerospace code (but obsolete for precession). | | 2013 | "Explanatory Supplement 2013 Sean Urban PDF" | Modern professional work. Required for JWST, Gaia DR3, and modern asteroid tracking. |
Most are either the out-of-copyright 1961 edition mislabeled as 1992, or they contain malware. The 1992 edition is worth supporting – nothing else explains the leap second, TT vs TDB, and the ICRS so clearly. the explanatory supplement to the astronomical almanac pdf
How do we know where Jupiter will be in 2060? The supplement explains planetary perturbation theory, the use of Chebyshev polynomials in the DE (Development Ephemeris) series from JPL, and how to interpolate these tables. | Edition | Keyword Add-on | Best For