The Goddard Space Flight Center's main campus is located within Greenbelt, Maryland, about 6.5 miles northeast of Washington, D.C. The center is a major U.S. laboratory for developing and operating unmanned scientific spacecraft. Goddard manages many of NASA's Earth observation, astronomy and space physics missions. The campus encompasses 1,270 acres, part of which is loaned by the nearby U.S. Department of Agriculture. These grounds include more than 34 buildings that provide more than 3 million square feet of research, development and office space. Goddard also maintains the adjacent Magnetic Test Facility, Propulsion Research site, the Antenna Performance Measuring Range, and the Optical Tracking and Ground Plane Facilities. NASA has ownership of 1,121 acres of land in Greenbelt. The remaining 149 acres are the outlying sites and are held by revocable lease from the U.S. Department of Agriculture.