AARTFAAC takes another step towards real-time deployment

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Clik here to view.© AARTFAAC group

The AARTFAAC project piggybacks on the LOFAR superterp stations in order to implement a commensal, near real-time All-sky monitor for transient sources. This is achieved by additional hardware in the stations which tap the station RSP ring network and reformat the data, before routing them to Groningen for correlation with a GPU based system.

Needless to say, the 288 dual-pol inputs passing through multiple hardware, and arriving at ~30 Gbps on the GPU machine provides ample scope for generating formatting and other issues.

Recently, we were able to verify the correctness of the data chain from the stations, through the AARTFAAC station hardware, and upto the output of the correlator.

Now, the calibration and imaging component of the pipeline has also been verified. This block carries out per-dipole calibration, including compensation for ionospheric refraction, and subtracts the A-team to generate images with a dynamic range of ~2000:1. The above gif shows such a sequence all-sky images in the XX polarization, over a timespan of a minute during the night of 08Nov14. Each image has an integration time of 1 second, and a bandwidth of 1 subband (~200 kHz) around 57 MHz. The LBA_OUTER array configuration was used. In the image, sources from the 3C catalog with a flux above 50 Jy are indicated by their 3C numbers, while the flux colorbar is in arbit. units.

The correlator latency is about 0.45 sec, with the calibration and imaging taking about 0.25 second per frequency channel. The next step for AARTFAAC is interfacing to the transients pipeline (TraP), which will do the actual job of transient detection via image plane lightcurve extraction and analysis.

Stay tuned for more exciting news!