pitch however in response to instructions from processor 167 which in turn receives u201c terrain just ahead u201d data 184 and other position and mapping information from the terrain analysis computer 185 boom 192 can also move from side to side to replicate roll u2014 the sideways tilt of the place where the proxy robot will be walking some ten minutes in the future together these boom movements account for both pitch and roll two of the three movements possible in three dimensional space the third element is yaw u2014 in this case the direction the handler is facing or moving on a 360 degree plane this element is determined by the handler and is translated into heading signals 171 which together with step distance 172 and step moment 173 data are packaged and translated by handler step motion data electronics 166 into u201c follow me u201d proxy robot language 169 to guide the proxy 39 s every move the u201c follow me u201d data that travels over an uplink path to mars or whatever remote mission location arriving at the exact moment anticipated by terrain analysis computer 185 fig5 a illustrates a scene on the moon rendered pictorially while fig5 b depicts the same scene in 3d bar chart form in the photographic version of the scene 200 top we see two hills with summits 201 and 205 with a saddle 203 between them in front of.