The AMISR concept entails the use of a large number of identical
electronic subsystems, which yields a high degree of redundancy and a
robust response to hardware failures. The systems as a whole have proven
to be exceptionally reliable, as evidenced by the nearly continuous
PFISR coverage since it began normal operations in 2007. The high-level
of redundancy in an AMISR system is in so small part responsible for
AMISR’s amenability to largely unattended remote operations. AMISR is the only system in the world with similar capabilities that can be operated with so little on-site staffing.
The AMISR systems are highly modular. The various subsystems operate synchronously via a combination of Ethernet/software constructs and specialized hardware signaling. The figure above shows the components that go into an AMISR system.
- The basic element of an AMISR system is the radar front-end Tx/Rx module, called an Antenna Element Unit (AEU). The AEU includees a 500-Watt solid state power amplifier (SSPA), designed and manufactured by SRI International, as well as a cross dipole antenna. The design of the AEU is conducive to plug-and-play upgrades. Each AEU consists of low-level RF circuitry for phase control on
transmit and receive, a low noise amplifier that sets the overall system
receive sensitivity, a Solid State Power Amplifier (SSPA) to generate
the transmitter RF, a power supply, and digital control and
- 32 AEUs are arranged on an AMISR panel that contains a Panel Control Unit (PCU) for AEU control and monitoring. The PCUs each include a fully programmable computer running Linux so
that the functionality of the array can be adjusted and upgraded over
time. On a standard AMISR face, 128 identical AMISR panels are
nominally arranged in a densely-packed and roughly square configuration.
- The prime power for the radar, on the other hand, is routed through two Utility Distribution Unit (UDU)
vans. The radar runs off of aircraft-standard 400 Hz power, which is
generated by eight JetPower units with four in each UDU van. Each JetPower unit powers 16 panels.
- The overall control of the system is driven from an Operation and Control Center (OCC) that houses general-purpose computers as well as low-level RF signal conditioning modules. Physically, the OCC is an environmentally controlled shelter or building available for operator interaction with the system, though most interactions in fact occur over the internet whether the operator is in the OCC or not. The OCC also houses all of the data acquisition channels, and contains the source for the transmitted waveforms and (at PFISR) RF receive signals from 16 equally sized portions of the array (representing a 4x4 grid).