Propulsion

The 24 multipurpose liquid-propellant ( hydrazine) thrusters provided several functions: spacecraft attitude control, trajectory/orbit correction, and reaction-wheel desaturations. Positioned in the middle of the 10-sided equipment bus was the single propellant tank that, at launch, contained monopropellant hydrazine. A helium tank was attached to the struts of the propulsion-module structure and was used, if necessary, to offset a drop in the pressure of the hydrazine system, a drop that would reduce thruster output level.