Radio array of portable interferometric detectors (RAPID)

The Radio Array of Portable Interferometric Detectors (RAPID) is a new radio array with a flexible architecture. The instrument uses per element software defined radios and a software signal processing architecture to enable the flexible study of a wide range of natural phenomena using radio imaging techniques. The array will be used for investigations of ionospheric phenomena, solar radio emission, the Galactic synchrotron background, and ultra-high energy cosmic rays via air-shower emission. The array will consist of ~100 small, low gain antennas operating over a frequency range of 48 to 450 MHz. RAPID is designed to make flexible and coherent radio observations, capturing the amplitude and phase of the electric field across a user-defined aperture with easily reconfigurable spatial sampling. Key technical elements include a novel absolute broadband antenna calibration method, elimination of a clock distribution network with a compact, low power chip scale atomic clock in each unit, state-of-the-art high performance voltage data recording, and low power consumption, via use of the latest low-power A/D converters and digital processing chips. By minimizing the power per element the RAPID system will be able to use compact, portable solar panels and batteries. Unlike existing arrays, RAPID will be operated without any cabling between the antennas and a central location, and can be shipped, deployed and physically reconfigured quickly and easily with zero site infrastructure. This creates a unique capability to locate and configure an imaging radio interferometer array, highly customized to the specific science goal of any given field campaign, thereby supporting science investigations that have not before been feasible. When used in conjunction with existing incoherent scatter radar transmitters or other transmitters of opportunity the array will provide a flexible capability for radar imaging of coherent and enhanced backscatter (e.g. E and F-region irregularities; naturally or artificially enhanced ion acoustic lines). The RAPID system architecture is based on voltage data capture with all processing performed in software, simplifying field operations and reducing equipment complexity. Data and work-flow management for the system will exploit distributed messaging, cloud technologies for scalable processing, and be implemented using open source Object Oriented Data Technology (OODT) software.