The Long Wavelength Array and Its Potential for Ionospheric Measurement and Specification

摘要

The Long Wavelength Array (LWA) is a very large radio-telescope currently under construction in the state of New Mexico in the southwestern United States. The LWA will consist of 53 stations with electronic phased-array capability operating in the 20-80 MHz frequency range. Ionospheric effects at these frequencies can be problematic and will make absolute measurements of source fluxes and high quality astrophysical imaging difficult to accomplish. We describe a method for ionospheric monitoring and correction that may form the basis for LWA ionospheric correction. The method is the rapid all-sky calibration (RASCAL) technique that will be used to measure and characterize differential total electron content between the LWA and all visible astronomical radio sources above a certain cut-off flux. We also assess the application of the RASCAL measurements for volumetric tomographic reconstruction of the electron density distribution over the volume covered by the measurements.