FPGA Cluster Computing in the ETA Radio Telescope

Array-based, direct-sampling radio telescopes have computational and communication requirements unsuited to conventional computer and cluster architectures. Synchronization must be strictly maintained across a large number of parallel data streams, from A/D conversion, through operations such as beamforming, to dataset recording. FPGAs supporting multi-gigabit serial I/O are ideally suited to this application. We describe a recently-constructed radio telescope called ETA having all-sky observing capability for detecting low frequency pulses from transient events such as gamma ray bursts and exploding primordial black holes. Signals from 24 dipole antennas are processed by a tiered arrangement of 28 commercial FPGA boards and 4 PCs with FPGA-based data acquisition cards, connected with custom I/O adapter boards supporting InfiniBand and LVDS physical links. ETA is designed for unattended operation, allowing configuration and recording to be controlled remotely.