The National Radio Astronomy Observatory's 27 antenna Karl G. Jansky Very Large Array (NRAO VLA) is host to a commensal low frequency system called the VLA Low-band Ionosphere and Transient Experiment (VLITE). This system currently records data from 16 of the primary focus 330 MHz feeds during nearly all observing programs that use one of the eight Cassegrain receivers. This type of commensal (or piggy-back) system provides a powerful opportunity to increase the scientific capabilities of an instrument, yet it is accompanied by numerous complexities resulting from lack of control over the observational setup. In this paper we specifically investigate the stability of the instrumental bandpass response as recorded by VLITE. We demonstrate that the bandpass for each antenna is stable for long periods of time. This allows the use of a global bandpass derived from high signal-to-noise ratio observations of reliable calibrators, which may be applied to any dataset. This method avoids the loss of data when a bandpass cannot be calculated because the appropriate calibrators are not observed, not observed for long enough, or when the observations are severely impacted by radio frequency interference. We also demonstrate that monitoring the behavior of the bandpass solutions over time can be a powerful tool to determine intermittent equipment issues, as well as long term changes to the system.
Tracy E. Clarke, Henrique Schmitt, Simona Giacintucci, and Wendy Peters, "Investigating global instrumental response for the JVLA low band ionosphere and transient experiment (VLITE)," Proc. SPIE 10704, Observatory Operations: Strategies, Processes, and Systems VII, 107040I (Presented at SPIE Astronomical Telescopes + Instrumentation: June 12, 2018; Published: 10 July 2018); https://doi.org/10.1117/12.2312383.
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