Satellites in low Earth orbit (LEO, below 2000 km or 1243 miles) and medium Earth orbit (MEO, between 2000 and 35,786 km or 1,243 and 22,236 miles) are less common, operate at lower altitudes, and are not fixed in their position above the Earth. Lower altitudes allow lower latencies and make real-time interactive Internet applications more feasible. LEO systems include Globalstar and Iridium. The O3b MEO constellation is a medium Earth orbit system with a latency of 125 ms. COMMStellation™ is a LEO system, scheduled for launch in 2015, that is expected to have a latency of just 7 ms.