The OLYMPEX field campaign took place over the Olympic Peninsula of Washington during winter 2015-2016. During the intensive observing period, several aircraft flights obtained multi-frequency airborne radar measurements at X-, Ku-, Ka, and W-band from radars aboard the ER-2 and DC-8 aircraft. In addition, ground radars at S- and X-band performed RHI scans under the aircraft ground tracks. These coincident datasets provide a wealth of complementary information about the hydrometeor particle sizes, shapes, and orientations.In order to synthesize these measurements and test the robustness of scattering models, an optimal estimation retrieval based upon a Hitschfeld-Bordan profiling algorithm has been developed. This algorithm retrieves profiles of the particle size distribution parameters Nw and Dm, and, in the ice phase, relative proportions of aggregate, pristine, and rimed particles, using scattering models with different size-density and size-aspect ratio relationships. Under this formulation, only the pristine particles are horizontally aligned and capable of producing non-zero ZDR and KDP.From the nadir-looking airborne multifrequency radars, we find that aggregates may be readily distinguished from rimed and pristine particles owing to their uniqueness in triple-frequency space. However, rimed and pristine particles occupy a similar region in this space and thus polarimetric measurements greatly enhance their identification in our retrieval framework. With these capabilities we will present analyses of three-dimensional hydrometeor mapping obtained during various OLYMPEX cases. Some features retrieved in these cases include a layer of enhanced aggregation about 2km above the melting layer, hypothesized to be maintained by orographic uplift. This layer is often situated above a layer of denser, aligned particles. Regions of riming and supercooled liquid water beneath generating cells are also identified by our retrieval algorithm. Comparisons to in-situ observations and evaluation of scattering models will be presented.
A critical component of the Global Precipitation Measurement (GPM) Mission validation strategy involves use of dual-polarimetric (DP) ground-based radar (GR) products. Both operational and research DP radars across the U.S. and several international locations are used with coincident GPM dual-frequency precipitation radar (DPR) data in a significant expansion of the original TRMM-based “validation network architecture” (VN; Schwaller and Morris, 2011, J.Tech.). The VN radar databases consist of millions of geometrically matched DPR and GR precipitation volumes. Not only does it serve as a tool for validation of satellite-based precipitation retrieval algorithms and GR calibration but also a valuable resource for precipitation science and for complimenting future convective precipitation-related satellite missions.
We have designed and tested a digital receiver suitable for the reception of 6 GHz instantaneous baseband signals. It is based on a Tektronix TADC-1000 12.5-GS/s 8-bit digitiser module, a Tektronix TIPA-3100 HAPS Interposer board and a Synopsys HAPS62-Virtex6 Prototyping Motherboard. This motherboard is also employed for filtering and signal processing. The ADC module uses an external clock from the interposer board and can accept a range of input clock frequencies between 1.6 and 3.125 GHz, resulting in sample rates of between 8 and 12.5 GS/s in single-channel mode. The external clock and digital data are supplied to and processed via the HAPS62 board. A 2048-channel weighted overlap-add (WOLA) and FFT structure separate the input signal into approximately 5-MHz sub-bands to allow subsequent high-resolution processing to obtain continuous spectral information over the input bandwidth. This system meets present-day demands on high-resolution wideband digital back-ends for RF spectrum monitoring. This technology could be part of the next generation wideband signal intercept systems for the future detection, classification and location of modern complex RF signals.
One of the major issues in testing Automatic Target Recognition (ATR) systems lies in having a sufficient amount of trusted data to be able to estimate efficiency and reliability of the developed algorithms. Generally synthetic data is used because real world data is not easy to obtain or too expensive for academic research. This paper describes an original low-cost automatic acquisition system designed to build a database of RCS acquired with real planes (airliners), in bistatic configuration, at low frequency (VHF). The described system uses ADS-B for target position and a network connected set of Software Defined Radio (SDR) receivers for RF processing. This setup was used to build a RCS database of 1300 commercial airliners in less than two weeks close to Paris-Orly international airport. The webbased graphical user interface was used over this time to remotely monitor the system and make demonstrations.
Radar and electronic warfare (EW) systems operate in an increasingly cluttered electro-magnetic (EM) environment. Evaluating system hardware with a variety of spectral and emitter scenarios helps characterize system performance in the presence of multiple emitters of interest and potential interferers that can be either non-intentional or intentional. DAC technology has evolved to the point where wide instantaneous bandwidths and high resolution is available with the current generation of arbitrary waveform generators (AWG). The true power of an AWG is in its ability to generate virtually any waveform downloaded into its memory making it easy to create radar and communications emitters scattered across a synthetic test range that simulates thousands of cubic miles of airspace. This paper will propose new approaches to spectrum and emitter simulation using high precision AWGs and investigate their use in applications which in the past have required a much more complicated, costly and multi-instrument solution. It will explore unique methods for baseband waveform creation, extending scenario length through the efficient use of memory, and upconversion of wideband composite signals to RF and microwave frequencies.
