A method for spherical harmonic analysis of Compton - Getting corrected 3-D energetic particle distributions

A method is described whereby a particle distribution measured by a number of telescopes (four in this application), observing the whole sky, mounted upon a spinning spacecraft, can be resolved into a set of spherical harmonics. The coefficients of the expansion are used to estimate the anisotropy of the particles and components of the anisotropy in different frames of reference (e.g., solar wind frame, RTN frame, spacecraft frame, etc.) for specific energy channels. For the transformation of the distribution function between frames of reference moving each other, the respective Compton-Getting correction is performed by a new geometrical approach. The respective energy change is also evaluated.