OSIRIS-REx Mission Gravity Assist
After a year orbiting the sun, OSIRIS-REx will make a flyby of Earth. Earth's gravitational field will pull the spacecraft towards the planet where it can "borrow" a small amount of Earth's orbital energy. This additional energy is used to increase OSIRIS-REx's orbital inclination and sling it back into space for a rendezvous with Bennu.
For more information, visit the OSIRIS-REx webpage at http://www.asteroidmission.org/mission/