Signal processing is an integral part of the radio astronomy process. It is used for pre-processing data for specific science requirements in preparation for making the stunning high-resolution radio images that the SKA will eventually produce.
Signal processing also handles the complex operation of beam-forming, which enables the radio signals to initially be received from across the sky from any direction, and with the SKA, in multiple directions at the same time.
Optical cross connects, similar to the technology shown in the first image on this page, channel data from the receivers to the correlator and are one of a variety of possible solutions for the SKA currently being tested.
The cross-connect allows high speed switching of optical fibre signals. This is a cost and power efficient way of providing what is commonly referred to as a “corner-turn” on the data which will be needed for processes such as beam-forming and correlation.
The SKA will use signal processing to automatically detect the repetitive pulsed signal of objects such as pulsars (the collapsed spinning core of a dead star first discovered by Jocelyn Bell and Anthony Hewish) 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 events, which can temporarily brighten objects in the far reaches of the Universe, due to the gravity of a foreground object acting as a lens.
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 (A ratio of 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. The algorithms used will need to be as efficient as possible, to process the huge amounts of data coming through the system.
SKA signal processing has considerable processing and signal transport requirements due to its sheer scale of the array. Thousands of telescopes providing data simultaneously across two continents.
The signal processing will require exceptionally high-speed computer systems, that must meet budget, processing and thermal requirements.
Four signal processing technologies are currently being developed and tested by the astronomy engineering community, as potential solutions:
- General Purpose Processors
- Graphics Processing Unit (GPU)
- Field Programmable Gate Arrays (FPGA)
- Application Specific Integrated Circuit (ASIC)