The COSMIC system is a cluster of FPGA, CPU, and GPU hardware, which at all times receives a copy of digitized data streams from each of the VLA’s antennas. The data received by COSMIC necessarily reflects antenna-pointing, LO-tuning and digitization settings commanded by VLA observers, but otherwise operates completely independently. In particular, COSMIC is unaffected by any of the interferometric phasing, channelization, or correlation processes of the VLA’s facility instrument: WIDAR.
COSMIC comprises three main components:
A fiber optic splitter, which duplicates digitized data streams from the VLA antennas and delivers these to COSMIC digital instrumentation.
A small FPGA Cluster, which receives VLA antenna digitized data streams, channelizes these to 1 MHz frequency resolution, and transmits these data streams over multiple industry-standard 100 Gb/s Ethernet links.
A CPU/GPU Cluster which receives 1 MHz resolution data over Ethernet and performs a variety of digital signal processing operations, ultimately outputting SETI signals of interest (often referred to as "hits") into a database for further analysis.
And the CPU/GPU cluster in particular is extremely interesting:
The COSMIC CPU/GPU pipeline implements a beamformer, high-resolution channelizer, doppler-drift search, and calibration correlator. The configuration parameters of these algorithms may be varied in order to best leverage the array’s behaviour as dictated by the Primary Observer.
The COSMIC CPU/GPU processing pipeline is still under development, but will have the following capabilities:
Buffering of ∼ 5 minutes voltage data for all antennas in the VLA;
Beamforming of up to 32 coherent tied-array beams;
Incoherent beamforming;
Configurable frequency resolution between 1 MHz and 1 Hz;
Inter-antenna correlation (used for gain calibration observations) with millisecond time resolution; and
Doppler drift searching for narrow band signals (in antenna or beam data) with linear drift rates between -50 Hz/s and +50 Hz/s.
In normal operation, the COSMIC system will search for candidate signals with non-zero linear drift rates, and will permanently archive small data snippets (< 100 kHz bandwidth and < 5 minutes duration) around these events.
