Coordinate Systems for ACE

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The ISTP Project provides a Fortran library for conversion between these
coordinate systems.

A good description of how to make transformations between the different
coordinate systems can be found in a paper by M. A. Hapgood, "Space physics
coordinate transformations: A user guide", in Planetary and Space Science,
Vol. 40, No. 5, pp. 711-717, 1992.

J2000 GCI

     Geocentric inertial reference frame using the Julian Epoch of Jan. 1,
     2000.
     At the Julian Epoch,
          X = Earth's mean vernal equinox
          Z = Earth's mean spin axis

RTN - Radial Tangential Normal

     Spacecraft centered coordinate system.
     R = Sun to Spacecraft unit vector
     T = (Omega x R) / | (Omega x R) |
          where Omega is Sun's spin axis (in J2000 GCI)
     N completes the right-handed triad

GSE - Geocentric Solar Ecliptic

     X = Earth-Sun Line
     Z = Ecliptic North Pole

GSM - Geocentric Solar Magnetospheric

     X = Earth-Sun Line
     Z = Projection of dipole axis on GSE YZ plane

HSEa - Heliocentric Solar Ecliptic (Inertial)

     X = First Point of Aries
     Z = Ecliptic North Pole

HSEb - Heliocentric Solar Ecliptic (Earth Oriented)

     X = Sun-Earth Line
     Z = Ecliptic North Pole

HS - Heliocentric Solar

     X = Intersection between solar equator and solar central meridian as
     seen from Earth
     Z = North Pole of solar rotation axis

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Last Updated: Sep 15, 1998
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