English: STEREO mission designers determined that the most efficient and cost-effective way to get the twin obser­vatories into space was to launch them aboard a single rocket and use lunar swingbys to place them into their respective orbits. This is the first time lunar swingbys have been used to manipulate orbits of more than one spacecraft. Mission designers will use the moon's gravity to redirect the observatories to their ap­propriate orbits - something the launch vehicle alone can't do.