Mode 1 First Light (March 2012)
Development of the new VEGAS spectrometer continues rapidly. During March 2012, the VEGAS team, including local NRAO staff and members from UC Berkeley and West Virginia University, met in Green Bank to test an expanded prototype of the system. Eight ROACH FPGA boards and eight host computers were assembled to perform extensive system integration tests as well as to test and characterize the wide bandwidth capabilities that the spectrometer will provide. Test observations were performed to demonstrate the ability to process the entire 8 GHz band (spanning 18 to 26 GHz) provided by the central beam of the K-band Focal Plane Array (KFPA). In the present configuration, each ROACH board produces a 1024-channel, full Stokes spectrum with 1300 MHz of usable bandwidth. Thus the whole system can provide an aggregate bandwidth greater than 10 GHz. The spectrometers support integration times as short as 500 microseconds. Test observations were made on the bright pulsars B0355+54 and B0329+54 (see figure) to demonstrate the utility of the system for high frequency, wide bandwidth pulsar observations. This high frequency pulsar capability will be used to perform the most sensitive search yet for pulsars near the galactic center. The sensitivity of the KFPA and the spectrometers was also measured on the continuum calibrator source DR21. Development of the high resolution spectral line modes will continue through the summer.