Indian array proves a valuable test-bed for SKA transient survey
Using the Giant Metre-wave Radio Telescope (GMRT) in India and Graphics Processing Unit powered supercomputing at Swinburne University in Melbourne, the research team around our Curtin Associate Investigator Dr Ramesh Bhat was able to develop a transient detection pipeline. In their recent paper, they defined optimal observing strategies at frequencies of 325 and 610 MHz, where the GMRT offers highest sensitivity, processing 151 Terabytes of data from a 360 square degree patch of the sky.
The GMRT comprises 30 telescopes distributed over many square kilometres, so it constitutes a very good test-bed for operations with the Square Kilometre Array (SKA) – but the GMRT is located in an environment that is much more prone to radio frequency interference (RFI) than the SKA sites. The team exploited the GMRT’s software backend option of recording raw voltage data (in two polarisations) from the individual array elements; they then de-dispersed the data and searched for transient events by imaging known sources such as the Crab Pulsar.
In evaluating differences in the detection sensitivity of telescope elements, the researchers found that grouping the full telescope array into coherently summed sub-arrays and comparing the radio signals arriving at each sub-array greatly aided RFI identification and removal. A grouping into four sub-arrays delivered the best results by filtering out RFI and false alarms (due to receiver noise) but preserved the full imaging capability and sensitivity of the full telescope. The pipeline is intended to become part of a commensal program to run on the GMRT.