Aeronautical Engineering: A special bibliography with indexes, supplement 91, January 1978

This bibliography lists 359 reports, articles, and other documents introduced into the NASA scientific and technical information system in December 1977

Radar Technology

In this book “Radar Technology”, the chapters are divided into four main topic areas: Topic area 1: “Radar Systems” consists of chapters which treat whole radar systems, environment and target functional chain. Topic area 2: “Radar Applications” shows various applications of radar systems, including meteorological radars, ground penetrating radars and glaciology. Topic area 3: “Radar Functional Chain and Signal Processing” describes several aspects of the radar signal processing. From parameter extraction, target detection over tracking and classification technologies. Topic area 4: “Radar Subsystems and Components” consists of design technology of radar subsystem components like antenna design or waveform design

Applied Radar Meteorology

This is a textbook focused on operational and other aspects of applied radar meteorology. Its primary purpose is to serve as a text for upper-level undergraduates and graduate students studying meteorology, who wish to work as professional operational meteorologists in the U.S. National Weather Service or the Air Force Weather Agency. In addition to a detailed description of operational weather radar systems operating in the United States, this text also provides a brief historical overview of the subject as well as a basic review of the physics of electromagnetic radiation and other theoretical aspects of weather radar. The last two chapters discuss a sample of other radar systems (such as the Doppler on Wheels and the Canadian and European operational networks), and future directions of weather radar, including its use as an input for high-resolution, rapid refresh computer models

Analytical evaluation of ILM sensors, volume 1

The functional requirements and operating environment constraints are defined for an independent landing monitor ILM which provides the flight crew with an independent assessment of the operation of the primary automatic landing system. The capabilities of radars, TV, forward looking infrared radiometers, multilateration, microwave radiometers, interferometers, and nuclear sensing concepts to meet the ILM conditions are analyzed. The most critical need for the ILM appears in the landing sequence from 1000 to 2000 meters from threshold through rollout. Of the sensing concepts analyzed, the following show potential of becoming feasible ILM's: redundant microwave landings systems, precision approach radar, airborne triangulation radar, multilateration with radar altimetry, and nuclear sensing

Ultra-low cross polarization antenna architectures for multi-function planar phased arrays

For over thirty years, single-beam mechanically steered radars have dominated the field of atmospheric observations, and since then, newer improved technologies have emerged that could provide a replacement for aging radars. Phased array radar technology offers meteorologists and scientists a unique opportunity to enhance weather forecasting through rapid electronic adaptive scans. Multiple array geometries exist for phased array radars (i.e., spherical, cylindrical, and planar); however, this work concentrates on enhancing the performance of planar antenna architectures. Planar phased array radar antennas have been under scrutiny due to the challenges posed when trying to satisfy all polarimetric weather requirements met by conventional parabolic dish reflectors (e.g., co-polarized beam mismatch under 0.1 dB, input isolation higher than 40 dB, cross-polarized radiation under -40 dB). This dissertation takes a fresh look into the electromagnetic characteristics of traditional antennas used in planar phased array geometries and provides mathematical insight to prove their performance, limitations, and advantages. The metrics used to evaluate essential performance characteristics were bandwidth, scanning range, polarization, co-polarized beam match, cross-polarization, isolation, and intrinsic cross-polarization (IXR). The antennas presented in this work (i.e., Horus, Polarimetric Atmospheric Imaging Radar (PAIR), and Horus-ONR) were validated by comparing the results of predictive simulating tools against physical antenna measurements. The Horus antenna was made using aperture coupling feeding technique with stacked microstrip patches. It achieved a fractional bandwidth of 15.4%, a co-polarized beam mismatch of 0.08 dB, and scanned cross-polarization levels of -29 dB, based on Ludwig’s third definition of polarization for θ = ± 45°. The PAIR antenna was made using balanced probe-fed stacked microstrip patches and it totaled fractional bandwidths of 7.7%, co-polarized beam mismatch of 0.21 dB, and -40 dB cross-polarization within the required imaging field of view. Lastly, the Horus-ONR antenna. Its design follows Horus guidelines for manufacturing but improves bandwidths up to 24.8% by trading the scanned co-polarized beam mismatch and cross-polarization required for weather missions. Other antenna architectures proposed for future phased array radar developments are the ultra-low cross-polarization microstrip patch (ULCP-MPA) and a dielectric covered slot antenna (ULCP-DCSA). The ULCP-MPA and the ULCP-DCSA can achieve cross-polarization levels of -40 dB for θ = ± 45°. The antenna designs presented in this dissertation show the lowest scanned cross-polarizations with highly calibratable polarization and might be the best planar radiating elements present in literature so far, despite not achieving all polarimetric weather requirements for multi-function phased array radars. Microstrip patch antennas offer a scalable, low profile solution with excellent polarization diversity and reasonable scanned bandwidths for multi-function, planar phased array radar platforms of the future

Signal Processing Techniques and Concept of Operations for Polarimetric Rotating Phased Array Radar

The Weather Surveillance Radar 1988 Doppler (WSR-88D) network has been operational for over 30 years and is still the primary observational instrument employed by the National Weather Service (NWS) forecasters to support their critical mission of issuing severe weather warnings and forecasts in the United States. Nevertheless, the WSR-88Ds have exceeded their engineering design lifespan and are projected to reach the end of operational lifetime by 2040. Technological limitations may prevent the WSR-88D to meet demanding functional requirements for future observational needs. The National Oceanic and Atmospheric Administration (NOAA) has started considering radar systems with advanced capabilities for the eventual replacement of the WSR-88D. Unique and flexible capabilities offered by Phased Array Radar (PAR) technology support the required enhanced weather surveillance strategies that are envisioned to improve the weather radar products, making PAR technology an attractive candidate for the next generation of weather radars. If PAR technology is to replace the operational WSR-88D, important decisions must be made regarding the architecture that will be needed to meet the functional requirements. A four-faced planar PAR (4F-PAR) is expected to achieve the requirements set forth by NOAA and the NWS, but deploying and maintaining an operational network of these radars across the U.S. will likely be unaffordable. A more affordable alternative radar system is based on a single-face Rotating PAR (RPAR) architecture, which is capable of exceeding the functionality provided by the WSR-88D network. This dissertation is focused on exploring advanced RPAR scanning techniques in support of meeting future radar functional requirements. A survey of unique RPAR capabilities is conducted to determine which ones could be exploited under an RPAR Concept of Operations (CONOPS). Three capabilities are selected for further investigation: beam agility, digital beamforming, and dwell flexibility. The RPARs beam agility is exploited to minimize the beam smearing that results from the rotation of the antenna system over the collection of samples in the coherent processing interval. The use of digital beamforming is investigated as a possible way to reduce the scan time and/or the variance of estimates. The RPAR's dwell flexibility capability is explored as a possible way to tailor the scan to meteorological observations with the goal of improving data quality. Three advanced RPAR scanning techniques are developed exploiting these capabilities, and their performance in support of meeting the radar functional requirements is quantified. The proposed techniques are implemented on the Advanced Technology Demonstrator (ATD), a dual-polarization RPAR system at the National Severe Storms Laboratory (NSSL) in Norman, OK. Data collection experiments are conducted with the ATD to demonstrate the performance of the proposed techniques for dual-polarization observations. Results are verified by quantitatively comparing fields of radar-variable estimates produced using the proposed RPAR techniques with those produced by a well-known collocated WSR-88D radar simultaneously collecting data following an operational Volume Coverage Pattern (VCP). The techniques introduced are integrated to operate simultaneously, and used to design an RPAR CONOPS that can complete a full volume scan in about one minute, while achieving other demanding functional requirements. It is expected that the findings in this dissertation will provide valuable information that can support the design of the future U.S. weather surveillance radar network

UAV-Based In Situ Antenna Characterization: Analysis and Design Requirements

This thesis proposes to characterize antennas in situ with Unmanned Aerial Vehicles (UAVs), especially within the framework of weather radar and 5th generation wireless systems (5G) antennas. Specifically, it is concerned with devising the requirements and tradeoffs of such a system. Characterizing an antenna in its operational environment is important to ensure that it meets its performance requirements, once it is installed in a larger system. Several techniques exist to carry out this task. Balloon-tethered dipoles at different heights were used to measure antennas radiation patterns in elevation as early as 1965. In 1988, helicopters replaced balloons and permitted the measurement of any antenna radiation pattern cut. In 2014, UAVs emerged to carry out this task for VHF and UHF antennas only, pointing at zenith, and with low directivity. However, measuring high-gain antennas pointing at low elevation angles presents more challenges, which this thesis takes into account. First, requirements for weather radar systems as well as 5G base station antennas are listed, as well as general measurement requirements, including phase, amplitude, ground reflection, and link budget requirements. Then, the requirements and tradeoffs for characterizing antennas using UAVs are presented. The different scanning strategies are exposed, as well as the necessary distance for measuring antenna pattern cuts. The effect of ground reflections on the measurements is set forth. The positioning accuracy of a UAV platform, specifically of its Global Positioning System (GPS), Inertial Measurement Units (IMUs), and gimbal, is presented, with a focus on the in-house Advanced Radar Research Center (ARRC) hexacopter. The effects of the UAV position and gimbal drifts on the measurements are formulated theoretically, and illustrated. Two radiating structures to be mounted on the UAV are studied---a 3x3 and a 2x2 dual-polarized patch antenna arrays, with different UAV platforms---the in-house ARRC hexacopter and octocopter as well as the DJI Phantom 3. Following is a presentation of the design process of a UAV platform, with an emphasis on the required performance factors pertaining to in situ antenna characterization. Finally, a proof of concept of this system is shown, using a commercially available UAV---DJI Phantom 3---equipped with a quarter wavelength monopole antenna that measures a custom traveling wave antenna

The design of an experiment to determine the limitations imposed on a multiple-aperture antenna system by propagation phenomena final report

Design of experiments to determine effects of propagation phenomena on operation of multiaperture antenna arra

Marshall Space Flight Center Research and Technology Report 2018

Many of NASAs missions would not be possible if it were not for the investments made in research advancements and technology development efforts. The technologies developed at Marshall Space Flight Center contribute to NASAs strategic array of missions through technology development and accomplishments. The scientists, researchers, and technologists of Marshall Space Flight Center who are working these enabling technology efforts are facilitating NASAs ability to fulfill the ambitious goals of innovation, exploration, and discovery

Aeronautical engineering: A continuing bibliography with indexes (supplement 295)

This bibliography lists 581 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in Sep. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics