The Amsterdam-ASTRON Radio Transients Facility And Analysis Center (AARTFAAC)
all sky monitor is a sensitive, real time transient detector based on the Low
Frequency Array (LOFAR). It generates images of the low frequency radio sky
with spatial resolution of 10s of arcmin, MHz bandwidths, and a time cadence of
a few seconds, while simultaneously but independently observing with LOFAR. The
image timeseries is then monitored for short and bright radio transients. On
detection of a transient, a low latency trigger will be generated for LOFAR,
which can interrupt its schedule to carry out follow-up observations of the
trigger location at high sensitivity and resolutions. In this paper, we
describe our heterogeneous, hierarchical design to manage the 240 Gbps raw data
rate, and large scale computing to produce real-time images with minimum
latency. We discuss the implementation of the instrumentation, its performance,
and scalability.Comment: Submitted to Journal of Astronomical Instrumentation, Special issue
on 'Digital Signal Processing (DSP) in Radio Astronomy