| Term: | HGI |
| Definition: |
Heliographic Inertial - A heliocentriccoordinate system where the Z axis is normal to the solar equatorial plane,positive northward. X axis is along the intersection line between solarequatorial and ecliptic planes. The X axis was positive at SE longitude of74.367 deg on Jan 1, 1900. (See SE below.) Seehttp://nssdc.gsfc.nasa.gov/space/helios/coor_des.html |