Jet Propulsion Laboratory, California Institute of Technology
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 (Davies et al).
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 observation geometry parameters and related information as needed.
NAIF has designed the kernel file and software Toolkit architectures with flexibility as a principal goal. As an example, the SPICE ephemeris subsystem handles over a dozen different common representations of ephemeris data, such as Chebyshev, Lagrange and Hermite polynomials and classical conic elements. The addition of new data types is easily accomplished and will not impact the commitment to backwards compatibility.
Portability of software and kernel files is also a key requirement. SPICE Toolkit software and kernel files may be used on any platform that supports ANSI FORTRAN 77, and C language interfaces to the most used Toolkit subroutines are now being added.
A core set of SPICE components is in place and is available to the space science community, subject to NASA and JPL/Caltech licensing and distribution requirements. While the principle use is in the planetary science discipline, astrophysics, space physics and Earth science projects are also using this technology. SPICE-format ephemerides--called SPK files--for the natural bodies of our solar system are produced at JPL using the best available data from JPL's Solar System Dynamics Group (Yeomans, Standish, Jacobson et al). SPK files are also available from JPL for most NASA planetary missions, and for a small number of additional flight projects--both U.S. and international. However, any user can easily make SPICE kernel files.
Extension and adaptation of this core system to encompass broader functionality and to meet specific needs of new customers is an ongoing endeavor. The NAIF Group solicits suggestions for improvements from the astronomical community.
Acknowledgement:
Development of the SPICE system was carried out by the Jet Propulsion Laboratory,
California Institute of Technology, under contract with the National Aeronautics and
Space Administration.