Advanced EHF (AEHF)
The Advanced EHF (AEHF) constellation comprises six GEO satellites providing advanced encryption, anti-jam (frequency hopping and steerable nulls), low probability of detection (LPD), low probability of intercept (LPI) communications at data rates from 75 bps to 8 Mbps. As the successor to the US MILSTAR program, the constellation was designed to support the President, the National Security Council and high-level military leaders to control strategic and tactical forces, even in the event of a nuclear war.
The AEHF constellation provides coverage between latitudes of 65°N and 65°S. For northern polar regions, the Enhanced Polar System acts as an adjunct to AEHF to provide EHF coverage. Uplinks and crosslinks operate at EHF and downlinks operate at SHF. AEHF provide backwards compatibility to the LDR (75–2,400 bps) and MDR (4.8 kbps to 1.544 Mbps) provided by MILSTAR and adds extended data rates (XDR) of up to 8.192 Mbps.
Each AEHF satellite has a 44-GHz EHF receive phased array and two SHF 20-GHz transmit arrays; two satellite crosslinks; two uplink/downlink nulling antennas; one uplink/downlink Earth coverage horns; and six uplink/downlink gimbaled dish antennas. AEHF satellites use SSPA rather than TWTA.
The first satellite, AEHF-1 (USA-214), was successfully launched on 14 August 2010, but had difficulties in the transfer orbit, which delayed the program. AEHF-2 (USA-235) was launched on 4 May 2012. AEHF-3 (USA-246) was launched on 18 September 2013. AEHF-4 (USA-288) was launched on 17 October 2018. AEHF-5 (USA-292) was launched on 8 August 2019. AEHF-6 (USA-298) was launched on 26 March 2020.
AEHF satellites are used by the United States Armed Forces, the British Armed Forces, the Canadian Armed Forces, the Netherlands Armed Forces and the Australian Defence Force.
Supported user terminals include: Secure Mobile Anti-jam Reliable Tactical–Terminal (SMART-T), Single Channel Anti-jam Man Portable (SCAMP), Family of Advanced Beyond Line-of-sight Terminals (FAB-T), Submarine High Data Rate system, and Navy Multiband Terminals (NMT).