Advanced Extremely High Frequency (AEHF) is a series of communications satellites operated by the United States Air Force Space Command. They will be used to relay secure communications for the Armed Forces of the United States, the British Armed Forces, the Canadian Forces and the Royal Netherlands Armed Forces. The system will consist of six satellites in geostationary orbits, three of which have been launched. AEHF will replace the older Milstar system and will operate at 44 GHz Uplink (EHF band) and 20 GHz Downlink (SHF band).