Package org.orekit.frames

This package provides classes to handle frames and transforms between them.

The Transform class represents a full transform: combined rotation and translation, and their first time derivatives to handle kinematics.

Each Frame is defined by a transform linking it to another one, called its parent frame. The only exception is the root frame which has no parent. This implies that all frames are naturally organized as a tree with a single root. The predefined GCRF inertial frame was arbitrary chosen as the root for every tree.

The FramesFactory class implements several predefined reference frames. One set correspond to the frames from the various IERS conventions (ITRF and others). Other frames not belonging to the previous set are the EME2000 frame that was used prior to GCRF and which is linked to GCRF by a simple bias rotation, the MOD (Mean Of Date) frame which involves the IAU 1976 precession model, the TOD (True Of Date) frame which involves the IAU 1980 nutation model, the GTOD (Greenwich True Of Date) which involves the IAU 1982 Greenwich sidereal time model and the Veis 1950 frame which involves a Veis modified sidereal time model.

Some other frames are predefined outside of this package, in the CelestialBodies class. They correspond to the Sun, Moon, planets, solar system barycenter and Earth-Moon barycenter. For convenience, the very important solar system barycenter frame, which is the ICRF, can also be retrieved from the factory in this package even if it is really implemented in the bodies package.

The frames can be time dependent (for example the ITRF frame depends on time due to precession/nutation, Earth rotation and pole motion). In order to get a transform from one frame to another one, the date must be specified, and TransformProvider.getTransform(AbsoluteDate) is called under the hood. If a user wants to implement his own date synchronized frame, he has to implement his own TransformProvider class and provide it to the frame constructor.

Luc Maisonobe, Fabien Maussion, VĂ©ronique Pommier-Maurussane, Pascal Parraud