SMART-1 and the Moon

The solar electric primary propulsion on-board SMART-1 is a Stationary Plasma Hall-effect thruster, the PPS-1350 developed by SNECMA, France. Using Xenon gas as propellant and the power from the spacecraft's solar arrays, the thruster is capable of providing a thrust of something like 70 milliNewtons. Using the thrust of the electric propulsion system, SMART-1 progressively expanded its orbit, spiralling out from Earth and was caught by the Moon's gravitational field on 15 November 2004, nearly 14 months after launch. In order to enhance the capture opportunities and to save precious fuel, SMART-1 also made use of celestial mechanics, including Moon resonances and swing-bys. The spacecraft exploited the unstable regions of space where the gravity field of Earth and Moon compete and which are normally avoided by conventional trajectories. It passed through the L1 point of the Earth-Moon System which allowed for the spacecraft to be caught by the Moon's gravity.