Wide Field of View Imaging with a VHF Phased Array

摘要

The Long Wavelength Array (LWA; http://lwa.unm.edu/) is an ONR- funded project to design and construct a large, next-generation facility focusing on both ionospheric and astronomical research and operating in the high frequency (HF) and very high frequency (VHF) bands (20-80 MHz). The baseline design for the LWA consists of approximately 50 dipole-based phased- array stations, with each station consisting of 256 dual-polarization dipoles, distributed over approximately 400 km in the state of New Mexico. In operation, the stations themselves would be phased together to form a radio interferometer. The Long Wavelength Demonstrator Array (LWDA) was funded by NRL and developed jointly by NRL and the Applied Research Laboratories of the University of Texas at Austin (ARL:UT), with assistance from the University of New Mexico. The LWDA serves as a technology and scientific testbed for the LWA project by fielding prototype hardware and by providing experience with site preparation, radio frequency interference monitoring and mitigation, software development, environmental concerns, and initial science capability. The LWDA consists of 16 dual linear polarization dipoles, tunable in the frequency range of 60 to 80 MHz with an instantaneous received bandwidth of 1.6 MHz. The dipoles have an intrinsically large field of view (field of regard) and images of the entire sky are now being produced routinely. As part of the scientific prototyping work with the LWDA, these images are being used to search for transient celestial radio emitters at higher sensitivity levels than previously accessible. The LWDA also has obtained data, currently under study, containing passive radar observations of meteor scatter, anomalous propagation phenomena, and aircraft.