NASA's spice system models the solar system

The Navigation Ancillary Information Facility (NAIF) at Caltech's Jet Propulsion Laboratory acting under the directions of NASA's Office of Space Science, has built a data system-named SPICE-to assist scientists in planning and interpreting scientific observations. SPICE provides geometric and some other ancillary information needed to recover the full value of science instrument data, including correlation of individual instrument data sets with data from other instruments on the same or other spacecraft. The primary SPICE data sets are called ''kernels.'' One of these kernel types provides ready access to ephemerides of spacecraft, planets, satellites, comets and asteroids. A second kernel type provides a set of data specifying target body size, shape and orientation. These data are currently based primarily on IAU/IAG/COSPAR models. The SPICE system includes FORTRAN subroutines needed to read the kernel files and to calculate many common observation geometry parameters. Users integrate these SPICE ''Toolkit'' subroutines into their own application programs to compute needed information.