<h2>AAS 97-106</h2>
<h2> LISSAJOUS ORBITS AROUND HALO ORBITS                                                                                                             </h2>
<h4> G. Gmez and C. Sim, Universitat de Barcelona, Spain;  J. Masdemont, Universitat Politcnica de Catalunya, Spain                                                           </h4>
<h2> Abstract </h2>
 Apart from a general description of the libration orbits around a collinear  equilibrium point, the communication focuses in a semianalytical method, based on a  Lindstedt-Poincar procedure, to compute Lissajous orbits around a halo orbit.  The  series obtained for any of the RTBP coordinates x(t), y(t) and z(t), depend on two  frequencies and three amplitudes.  Two amplitudes (which are not independent) and  one frequency are related to a halo orbit.  The remaining amplitude is related to  the size of the Lissajous orbits around the halo orbit.