Dan Werthimer

A GPU-Based Wide-Band Radio Spectrometer

The Graphics Processing Unit (GPU) has become an integral part of astronomical instrumentation, enabling high-performance online data reduction and accelerated online signal processing. In this paper, we describe a wide-band reconfigurable spectrometer built using an off-the-shelf GPU card. This spectrometer, when configured as a polyphase filter bank (PFB), supports a dual-polarization bandwidth of up to 1.1 GHz (or a single-polarization bandwidth of up to 2.2 GHz) on the latest generation of GPUs. On the other hand, when configured as a direct FFT, the spectrometer supports a dual-polarization bandwidth of up to 1.4 GHz (or a single-polarization bandwidth of up to 2.8 GHz).

The Serendip II Design

Serendip II is an automated system designed to perform a real time search for narrow band radio signals in the spectra of sources in a regularly scheduled, non-Seti, astronomical observing program. Because we expect Serendip II to run continuously without requiring dedicated observing time, we hope to survey a large portion of the sky at high sensitivity and low cost. Serendip II will compute the power spectrum using a 65,536 channel fast Fourier transform processor with a real time bandwidth of 128 KHz and 2 Hz per channel resolution. After searching for peaks in a 100 KHz portion of the radio telescope’s IF band, Serendip II will move to the next 100 KHz portion using a programmable frequency synthesizer; when the whole IF band has been scanned, the process will start again. Unidentified peaks in the power spectra are candidates for further study and their celestial coordinates will be recorded along with the time and power, IF and RF frequency, and bandwidth of the peak.

Latest Results of the Sethi Survey at Arecibo

SETHi is a survey of the distribution of galactic neutral hydrogen being performed comensally at the NAIC Arecibo Observatory. At the same time that observers use receivers in the Gregorian dome, SETHi is recording a 2.5MHz band centered at 1420 MHz from a flat feed on Carriage House 1. During normal astronomical observations, the SETHi feed scans across the sky at twice the sidereal rate. During 4 years of observations, we have accumulated over 15,000 hours of data covering most of the sky accessible to Arecibo. This survey has higher angular resolution than existing single dish surveys and higher sensitivity than existing or planned interferometric surveys.