Around the World in a Hundred Minutes

Abstract

Even though the first man-made spacecraft was only launched in 1957, satellite orbits had already been studied two centuries before this. Starting from Newton’s formulation of the law of gravity, scientists sought continuously to develop and refine analytical theories describing the motion of the Earth’s only natural satellite, the Moon. Today, several thousand man-made satellites orbit the Earth, together with countless pieces of space debris (Fig. 1.1).Much as celestialmechanics studied the laws ofmotion of solar system bodies, the branch of astrodynamics is concerned with the mathematical and physical description of artificial satellite orbits, as well as their control. Here, the term orbit refers to a trajectory that is essentially periodic in nature, and does not consider the special case of objects leaving the realm of the Earth towards interplanetary space.