On Sept. 22, NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security – Regolith Explorer) spacecraft will make a close approach to Earth, using the planet’s gravity to slingshot itself toward the asteroid Bennu. Over the course of several days, observatories and amateur astronomers with specialized equipment will be able to see OSIRIS-REx as the spacecraft approaches and retreats from its closest position over Earth, approximately 11,000 miles (17,000 km) above the planet’s surface.