|4||4||The ORBIT laboratory is comprised of several different test '''[wiki:Hardware/bDomains domains]''' in which experimenters can use the hardware provided by WINLAB for use in wireless experimentation. The Orbit grid as illustrated in Figure 1 consists of a multiply interconnected, 20-by-20 grid of '''[wiki:Hardware/hNodes ORBIT radio nodes]''', some non-grid nodes to control R/F spectrum measurements and interference sources, and front-end, application and back-end servers. These servers support various ORBIT services. In addition to the main grid, there are also 9 additional smaller //test grids//(a.k.a. sandboxes). All this is supported by the back end '''[wiki:Hardware/dInfrastructure orbit infrastructure]''' which provides services and control to the test facility.