## The Galileo Energetic Particles Detector

## Galileo EPD Handbook

### Chapter 2. EPD Software

**LGA Processing Software for
the Energetic Particles Detector ***(continued)*

*Source: C. Brull and S. Stone,
December 19, 1998*

**Appendix B. Coordinate Systems
***(continued)*

B.2 SPICE

All of the necessary physical data and ephemeris information necessary to compute the coordinate transformations described above is contained in the SPICE kernel files. Subroutines in the SPICE Toolkit provide access to the data contained in the kernel files. The SPICE Toolkit also contains subroutines to do vector and matrix operations.

B.2.1 Required Kernels

Three kernels are necessary to complete the coordinate transformations described in the previous section.

*-** **Leapseconds
Kernel*

The kernel contains information necessary to convert time
strings into ephemeris seconds past epoch J2000.

*-** **Planetary
Constants Kernel*

The kernel contains information regarding constants
associated with various planets. The orientationof Jupiter's
rotation axis along with the system III rotational rate are
contained in this kernel. The routine BODMAT uses this
information to create the conversion between inertial and
body-fixed coordinates.

*-** **Spacecraft
and Planetary Kernel*

The SP kernel contains position and velocity information for
given planets, moons, and spacecraft for a range of time.
The SPKEZ routine reads these kernels to determine the state
of a target body.

B.2.2 Toolkit Routines

The following list describes the toolkit routines used in the above code segments. The descriptions are extracted from the subroutine library.

**BODMAT** Return
the J2000 to body equator and prime meridian coordinate
transformation matrix for a specified body.

**GSETRN_G** Return
the matrix that transforms coordinates from a specified
inertial reference frame to planetocentric solar ecliptic
coordinates.

**LATREC** Convert
from latitudinal coordinates to rectangular coordinates.

**MXM** Multiply
two 3x3 matrices.

**MXV** Multiply
a 3x3 double precision matrix with a 3-dimensional double
precision vector.

**ROTATE** Calculate
the 3x3 rotation matrix generated by a rotation of a
specified angle about a specified axis. This rotation is
thought of as rotating the coordinate system.

**RPD** Return
the number of radians per degree.

**SPKEZ** Return
the apparent state (position and velocity) of a target body
relative to an observing body, optionally corrected for
planetary (light time) and stellar aberrations.

Next: B.3 Verification of Results

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Updated 8/23/19, Cameron Crane

## QUICK FACTS

**Manufacturer:**The Galileo Spacecraft was manufactured by the Jet Propulsion Laboratory, Messerschmitt-BĂ¶lkow-Blohm, General Electric, and the Hughes Aircraft Company.

**Mission Duration:**Galileo was planned to have a mission duration of around 8 years, but was kept in operation for 13 years, 11 months, and 3 days, until it was destroyed in a controlled impact with Jupiter on September 21, 2003.

**Destination:**Galileo's destination was Jupiter and its moons, which it orbitted for 7 years, 9 months, and 13 days.