ARTICLE DE DÉMONSTRATION — synthèse pédagogique, et non rapport de mission RECA.
An orbit is a continuous fall. A spacecraft moves sideways fast enough that the Earth bends under it at the same rate as gravity pulls it. Altitude matters, but it's speed that creates the orbit.
Changing an orbit requires changing the energy. A brief push can raise or lower the opposite side of the orbit, or tilt its plane. Engineers choose the time when each manoeuvre produces the most effect with the available energy.
The real missions rarely follow a perfect ellipse. Launch, waiting orbit, transfer, correction and arrival make up a carefully designed sequence. Each stage balances energy, navigational uncertainty, communications and the limitations of the craft.
References and further reading
