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Signal processing is an integral part of the radio astronomy process. It is used for pre-processing the data for specific science requirements in preparation for image formation and for beamforming, which enables the radio signals to initially be received from across the sky.
Optical cross connects, similar to the technology pictured, channel data from the receivers to the correlator and are one of a variety of possible solutions for the SKA.
A ribbon of optical fibres from each phased array feed (PAF) contains a set of frequency channels from every element in the PAF. The cross-connect allows the re-grouping of fibres such that a subset of frequency channels for all receivers can be mapped to a new ribbon and sent to down-stream processing nodes. This is a cost and power efficient way of providing what is commonly referred to as a “corner-turn” on the data needed for processes such as beam-forming and correlation.
The SKA will use signal processing to automatically detect the repetitive pulsed signal of a pulsar (the collapsed spinning core of a dead star) in the data. In addition to pulsars, the SKA will automatically detect transient events. These unexpected and unpredictable astronomical events include supernovae, gamma‐ray bursts and micro‐lensing. Both methods of auto-detection are time‐frequency based observations and require high time resolution data.
The SKA will stretch signal processing algorithm development in two vital areas. Faster and better ways will be developed to make the high dynamic range (106:1) images required for SKA science. Effective radio interference (RFI) mitigation algorithms will also be needed to enable observations across wide segments of the radio spectrum.
SKA signal processing has considerable processing and signal transport requirements due to its sheer scale whilst being constrained by cost and thermal dissipation. Four processing technologies are currently being developed and tested by the astronomy engineering community, as potential solutions:
- General Purpose Processor
- Graphics Processing Unit (GPU)
- Field Programmable Gate Arrays (FPGA)
- Application Specific Integrated Circuit (ASIC)
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