Contents

16 February 1990
Vol 247, Issue 4944

About The Cover

Graphical representation of the motion of satellite orbits in phase space (the space whose dimensions are position and momentum). Each point fixes the orbital eccentricity and argument of perigee; color bands correspond to constant energy levels. Rendered by contour “painting” on a massively parallel processor, the plot reveals a startling configuration of equilibria spawned by pitchfork and saddle node bifurcations. See page 833. [Computer graphics generated on a Thinking Machines Corporation CM-2 by Etienne Deprit and Liam Healy, Naval Research Laboratory, Washington, DC; photographic image by Mark Stucky]