Complex sentence: MGS used the data gathered from the Magellan mission to Venus to plan its aerobraking technique, using its solar panels as "wings" to control its passage through the tenuous upper atmosphere of Mars to lower the apoapsis of its orbit over the course of many months.
Split into simpler sentences: MGS used the data gathered from the Magellan mission to Venus to plan its aerobraking technique. The spacecraft used its solar panels as "wings" to control its passage through the tenuous upper atmosphere of Mars to lower the apoapsis of its orbit over the course of many months.