The Status of the ACRF Millimeter Wave Cloud Radars (MMCRs), the Path Forward for Future MMCR Upgrades, the Concept of 3D Volume Imaging Radar and the UAV Radar

Abstract

Executive SummaryThe United States (U.S.) Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) operates millimeter wavelength cloud radars (MMCRs) in several climatological regimes. The MMCRs, are the primary observing tool for quantifying the properties of nearly all radiatively important clouds over the ACRF sites. The first MMCR was installed at the ACRF Southern Great Plains (SGP) site nine years ago and its original design can be traced to the early 90s. Since then, several MMCRs have been deployed at the ACRF sites, while no significant hardware upgrades have been performed. Recently, a two-stage upgrade (first C-40 Digital Signal Processors [DSP]-based, and later the PC-Integrated Radar AcQuisition System [PIRAQ-III] digital receiver) of the MMCR signal-processing units was completed.Our future MMCR related goals are: 1) to have a cloud radar system that continues to have high reliability and uptime and 2) to suggest potential improvements that will address increased sensitivity needs, superior sampling and low cost maintenance of the MMCRs. The Traveling Wave Tube (TWT) technology, the frequency (35-GHz), the radio frequency (RF) layout, antenna, the calibration and radar control procedure and the environmental enclosure of the MMCR remain assets for our ability to detect the profile of hydrometeors at all heights in the troposphere at the ACRF sites.In the near-term (0-2 years), the ACRF should proceed with the upgrade of the remaining MMCR with the PIRAQ-III digital receiver. The upgrade (completed in early 2007) will bring commonality among the 5 operational MMCR at the ACRF sites, reduce the maintenance costs, and provide uniform temporal resolution and radar operational modes in all the ACRF sites. Each signal processing unit upgrade is estimated to ~$30K per MMCR.In the long term (2-5 years) the ACRF should pursue the development of a high-performance digital data processor and timing controller implemented in field-programmable gate arrays (FPGA) that will replace the existing intermediate frequency (IF) hardware/software and timing MMCR components. The digital radar transceiver will replace the analog radar waveform generator that generates the pulse compression (frequency modulation of the transmitted waveform technique that results to higher sensitivity) with a direct digital synthesis (DDS) PC-based card. Furthermore, the current IF section of the MMCR will be replaced with an FPGA-based digital receiver that will offer higher flexibility, direct control of the radar waveform through the DDS, and higher overall MMCR performance. This development can be the focus of DOE's Small Business Innovation Research (SBIR) (proposed in 2006, completed in 2008), with an objective to develop a digital radar transceiver and timing unit suitable for ground-based cloud and precipitation profiling radars that utilizes chirp pulse waveforms and fast Fourier transform (FFT) processing for superior performance and multi-functionality. This development should be the ...