ESA Science & Technology - Reboost Strategy: Reaction Wheel Offloading

The perilune raising manoeuvre strategy consists of a series of reaction wheel off-loadings combined with intermittent thrust centred around apolune during 74 orbits.  The assymetric firing of the attitude thrusters will produce a small Δv in the direction of flight (to the right in this illustration).  The reaction wheel offloadings transfer spacecraft angular momentum between the spacecraft +Y and -Y axis, also generating a small Δv in the direction of flight.  The accumulative Δv of the 74 orbits will result in the raising of SMART-1's perilune altitude by ~90 km.