The Advanced Extremely High Frequency (AEHF) satellite network has entered its initial operational phase, after completing a series of tests simulating battlefield and cyber-attack situations. Built by Lockheed Martin Space Systems, with Northrop Grumman supplying the antenna payloads, the AEHF network was designed to support protected two-way communications for tactical military forces. With initial tests completed, the system’s international partners—the United States, Canada, the Netherlands, and United Kingdom—will have access to the satellites for military and government operations.
Three nuclear-hardened AEHF satellites are currently in operational orbit. The network was designed with security and signal integrity in mind, insulating communications against jammers, cyber-attacks, and interference. The high data rates and network capacity provide a wide range of services to soldiers and government agents in compatible aircraft, naval vessels, and vehicle. These include data networking, video broadcasting, targeting data, voice conferencing, and strategic report back, among others.
Advantages over Legacy Systems
The AEHF system has significant advantages over its predecessor, the legacy Milstar satellite network. Mark C. Calassa, vice president of protected communications systems at Lockheed Martin, says that the AEHF network transmits data five times faster than legacy satellites and has almost 10 times the capacity. The satellites are designed with an extended data rate (XDR) waveform that pulls transmission speeds up to 8.192 Mbit/s. At the same time, the payloads are backwards-compatible with the Milstar’s low data rate (LDR)—75 to 2400 bit/s—and medium data rate (MDR)—4.8 Kbit/s to 1.544 Mbit/s—waveforms.
The satellites are connected by a series of bidirectional crosslinks, creating an “on-board switchboard in the sky,” as Northrop Grumman phrased it in an article about the AEHF payloads. Exchanging information at 60 Mbit/s, these crosslinks allow the satellite network to process and relay signals directly instead of using vulnerable ground stations. The uplinks and crosslinks operate at 44 GHz in the EHF range, while downlinks operate at 20 GHz in the super-high frequency (SHF) range.
Anti-Jamming and Security Elements
The satellites are equipped with low-noise phased-array antennas, built from more than 10,000 MMICs based on indium-phosphate (InP). Along with flexible channel-to-beam mapping, the antennas direct the signal beams electronically, resulting in high-gain spot beams for unscheduled access for small portable terminals. In addition, two high-resolution antennas support tactical and strategic operations in the presence of in-beam jamming.
