Summaries of the Third Annual JPL Airborne Geoscience Workshop. Volume 2: TIMS Workshop

This publication contains the preliminary agenda and summaries for the Third Annual JPL Airborne Geoscience Workshop, held at the Jet Propulsion Laboratory, Pasadena, California, on 1-5 June 1992. This main workshop is divided into three smaller workshops as follows: (1) the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) workshop, on June 1 and 2; the summaries for this workshop appear in Volume 1; (2) the Thermal Infrared Multispectral Scanner (TIMS) workshop, on June 3; the summaries for this workshop appear in Volume 2; and (3) the Airborne Synthetic Aperture Radar (AIRSAR) workshop, on June 4 and 5; the summaries for this workshop appear in Volume 3

Summaries of the Third Annual JPL Airborne Geoscience Workshop. Volume 1: AVIRIS Workshop

This publication contains the preliminary agenda and summaries for the Third Annual JPL Airborne Geoscience Workshop, held at the Jet Propulsion Laboratory, Pasadena, California, on 1-5 June 1992. This main workshop is divided into three smaller workshops as follows: (1) the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) workshop, on June 1 and 2; (2) the Thermal Infrared Multispectral Scanner (TIMS) workshop, on June 3; and (3) the Airborne Synthetic Aperture Radar (AIRSAR) workshop, on June 4 and 5. The summaries are contained in Volumes 1, 2, and 3, respectively

Spaceborne sensors (1983-2000 AD): A forecast of technology

A technical review and forecast of space technology as it applies to spaceborne sensors for future NASA missions is presented. A format for categorization of sensor systems covering the entire electromagnetic spectrum, including particles and fields is developed. Major generic sensor systems are related to their subsystems, components, and to basic research and development. General supporting technologies such as cryogenics, optical design, and data processing electronics are addressed where appropriate. The dependence of many classes of instruments on common components, basic R&D and support technologies is also illustrated. A forecast of important system designs and instrument and component performance parameters is provided for the 1983-2000 AD time frame. Some insight into the scientific and applications capabilities and goals of the sensor systems is also given

Radar Testbed Characterization for Evaluation of Modulated Scatterer Concepts

The following research explores the concepts of communication-embedded radar with an emphasis on radar operation and modulated scatterer concepts. Once firmly established the concept of communication via radar backscatter could be used in a variety of fields including, mass data collection, SAR calibration, and military communication. A radar testbed was developed and charactersized to enable experimental evaluation of communication via modulated scatterer concepts. The radar operates with a 1.84-GHz center frequency and 75-MHz bandwidth (later upgraded to a 235-MHz bandwidth). A dual-channel arbitrary waveform generator is loaded with used-defined complex baseband signals for frequency upconversion for transmission via a 22 dBi parabolic reflector antenna. Backscattered signals are received and frequency downconverted on four identical channels, each fed by a dipole antenna. A 4-channel data acquisition system digitizes and records the output video signal at 1-GSa/s per channel for signal analysis. The primary means of evaluating the radar testbed were loopback and freespace setups. The loopback setup consisted of a cabled inserted between transmitter and receiver to provide a controlled propagation environment. In this setup results were shown to be desirable, and easily explained by theory. Linear FM (chirp) waveforms were used which enabled pulse compression to reduce the peak signal power while preserving range resolution. After pulse compression via matched filter routines, amplitude, phase, and resolution were characterized and found to agree with theory. In extending the tests to freespace, it was seen that near targets could be seen and resolved coherently across the 4 channels. A prototype modulated scatterer constructed by a senior design group was further tested to evaluate the prototype's viability. This scatterer impresses a bit sequency on the radar wavefrom by modulating the scatterer's termination impedance between an open and short circuit at a rate determined by the bit sequence to be communicated (similar to frequency-shift keying). Connected via a cabled-loopback configuration, the prototype was shown to impress a bit sequence onto the backscatter of the transmit chirp and, through processing, the bit stream associated with the modulated scatterer was decoded successfully. Followon testing will evaluate freespace operation and techniques for decoding information from multiple devices in the field of view. This radar testbed will be used to experiementally evaluate various modulated scatterer concepts as well as other radar-related waveform and signal processing concepts in the future

Publications of the Jet Propulsion Laboratory: 1990 and 1991

JPL Bibliography 39-32 describes and indexes by primary author the externally distributed technical reporting, released during calendar years 1990 and 1991, that resulted from scientific and engineering work performed or managed by the Jet Propulsion Laboratory (JPL). Three classes of publications are included: (1) JPL publications (90- and 91-series) in which the information is complete for a specific accomplishment; (2) articles from the quarterly Telecommunications and Data Acquisition (TDA) Progress Report (42-series); and (3) articles published in the open literature

Multifunctional metamaterial designs for antenna applications

Over the last decades, Metamaterials (MTMs) have caught the attention of the scientific community. Metamaterials are basically artificially engineered materials which can provide unusual electromagnetic properties not present in nature. Among other novel and special EM applications, such as the negative refraction index (NRI) application, Metamaterials allow the realisation of perfect magnetic conductors (PMCs), which are of interest in the development of smaller and more compact antenna systems composed of one or more antennas. In this context, this thesis is focused on investigating the feasibility of using metamaterial structures to improve the performance of antennas operating at the microwave frequencies. The metamaterial design process is challenging because metamaterials are primarily composed of resonant particles, and hence, their response is frequency dependent due to the dispersive behaviour of their effective medium properties. However, one can take advantage of this situation by exploiting those strange properties while finding other antenna applications for such metamaterial designs. For the case of the PMC applications, the relative magnetic permeability values are negative, because they are found just above the resonance of the metamaterial. This thesis investigates several antenna applications of artificial magnetic materials (AMMs). The initial work is devoted to the design of a spiral resonator (SR) AMM slab to realise a low profile reflector dipole antenna by taking advantage of its PMC response. The spiral resonator has been used due to its reduced unit cell size when compared to other metamaterial resonators, leading to a more homogeneous metamaterial structure. In addition, a bidirectional PMC spacer has been applied to produce a small and compact antenna system composed of two monopole antennas, although the concept may be applied to other antenna types. A third application as an AMC reflector are the transpolarising surfaces, where the incident electric field plane wave is reflected at a polarisation rotation angle of 90 degrees. Such surfaces may be of interest to produce high cross-polar response reflecting devices, like the modified trihedral corner reflector that has been tested for polarimetric synthetic aperture radar (PolSAR) purposes. Another application of the SR AMM metamaterial is the patch antenna with a magneto-dielectric loading. The relative magnetic permeability of the AMM metamaterial has values over the unity in the frequency band below the resonance. As a consequence, the patch antenna can be miniaturised without reducing its bandwidth of operation, in contrast to a typical high dielectric permittivity substrate. Finally, the SR AMM metamaterial also presents values of relative magnetic permeability between zero and the unity (MNZ). In such a case, the SR AMM metamaterial has been applied as an MNZ cover of a slot antenna, devoted to increasing the broadside radiated power and directivity of the antenna.En las últimas décadas, los Metamateriales (MTMs) han captado la atención de la comunidad científica internacional. Los metamateriales son básicamente materiales artificiales diseñados que tienen propiedades electromagnéticas inusuales no presentes en la naturaleza. Aparte de otras aplicaciones innovadoras en electromagnetismo, como la posibilidad de un material con un índice de refracción negativo (NRI), los metamateriales permiten realizar los conductores magnéticos perfectos (PMCs), que podrían ser de gran utilidad para implementar sistemas de múltiples antenas más pequeños y compactos. En este contexto, esta tesis se centra en investigar el uso de diferentes diseños de metamateriales para mejorar las prestaciones de sistemas radiantes o antenas que trabajan a frecuencias de microondas. El proceso de diseño de los metamateriales es complicado, porque los metamateriales están compuestos de resonadores magnéticos, y consecuentemente, su respuesta varía con la frecuencia a causa de la naturaleza dispersiva de sus parámetros de medio efectivo. No obstante, se pueden aprovechar estas propiedades extrañas para encontrar otras aplicaciones interesantes en antenas. Para el caso de aplicaciones como PMC, el valor de la permeabilidad magnética relativa toma principalmente valores negativos, ya que se encuentran después de la resonancia del metamaterial. Esta tesis realiza el estudio de diferentes aplicaciones de antenas con materiales magnéticos artificiales (AMMs). Primeramente, se ha diseñado un metamaterial AMM compuesto de resonadores en espiral (SRs), que se aplica para realizar un reflector de perfil bajo con una antena dipolo, aprovechando la respuesta PMC que proporciona el metamaterial. Se han utilizado resonadores en forma de espiral porque tienen una celda unidad más reducida al compararla con la de otros resonadores metamaterials, produciendo así una estructura metamaterial más homogénea. Además, un diseño PMC bidireccional ha permitido diseñar un sistema pequeño y compacto de dos antenas monopolo, aunque este concepto se puede aplicar a otros tipos de antenas. Una tercera aplicación como reflector AMC es el de pantalla transpolarizadora, dónde una onda eléctrica plana incidente es reflejada con un ángulo de rotación de 90 grados. Estas pantallas pueden servir para realizar dispositivos reflectores con una respuesta cruzada alta, como pasa con un triedro modificado que se ha probado con éxito en aplicaciones como calibrador de radar de apertura sintética polarimétrico (PolSAR). El metamaterial SR AMM también se ha utilizado como substrato magneto-dieléctrico de una antena impresa o patch. La permeabilidad magnética relativa de este metamaterial toma valores más grandes que la unidad en el rango de frecuencias por debajo de la resonancia. Por esto, la antena patch se puede miniaturizar sin reducir sus prestaciones de ancho de banda de operación, caso contrario a cuando se utilizan substratos de permitividad dieléctrica alta. Finalmente, el metamaterial SR AMM también toma valores de permeabilidad magnética relativa entre cero y la unidad (MNZ). En este caso, el metamaterial SR AMM se ha aplicado como un superestrato MNZ de una antena de ranura o slot, con la intención de incrementar la potencia radiada y la directividad de la antena

Pulsed radar measurements and related equipment

The purpose of this thesis has been to develop novel methods for pulsed radar measurements, creating practical tools for verifying the operation of a modern pulsed radar, and to build working prototypes suitable for field use. Very little information has been published in the radar field perhaps due to the military nature of many research projects. Methods and equipment are typically researched by different armed forces. In this thesis, some tools for frequency, power and waveform measurements are presented. Even the most modern commercial measuring instruments, however, are not capable of measuring a pulsed radar signal, mostly due to the short (even tens of nanoseconds) pulse length. The limitations of conventional measuring devices are discussed in the overview part of the thesis and also in Publications II and IV. The first publication demonstrates a radar calibration system, based on a fiber-optic delay line. The idea to use an optical delay line for such a purpose is not new, but an operational setup has not been published previously. The calibrator provides a convenient method to use the radar's own signal for calibration. The optical link makes it possible to use long delays, even tens of microseconds, without significant signal attenuation. Furthermore, two frequency measurement methods for short-term stability evaluation are presented. Both are based on a phase detector. The first setup has better frequency uncertainty, even 1.6 Hz, with a sampling speed of 10 000 s-1. The other setup is used to detect frequency differences: A deviation of 200 kHz in the carrier frequency could be detected when the pulse length was 200 ns. This system outperforms the first one when short pulses are evaluated. The phase detector based setup itself is old and familiar technology, but the idea to use it in this application is one thing new. Finally, two new instrumentation radars are also presented. They are used to measure the effects that terrain, weather, vegetation and seasonal changes have on radar clutter or signal propagation. A significant effort has been made by other scientists in developing mathematical models to be able to simulate the effects mentioned, but so far the only reliable method for creating clutter models is to collect data with a real radar. Such instrumentation radars have probably been developed earlier, but until now they have not been published

NASA Tech Briefs, June 1992

Topics covered include: New Product Ideas; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Workshop on Advanced Technologies for Planetary Instruments, part 1

This meeting was conceived in response to new challenges facing NASA's robotic solar system exploration program. This volume contains papers presented at the Workshop on Advanced Technologies for Planetary Instruments on 28-30 Apr. 1993. This meeting was conceived in response to new challenges facing NASA's robotic solar system exploration program. Over the past several years, SDIO has sponsored a significant technology development program aimed, in part, at the production of instruments with these characteristics. This workshop provided an opportunity for specialists from the planetary science and DoD communities to establish contacts, to explore common technical ground in an open forum, and more specifically, to discuss the applicability of SDIO's technology base to planetary science instruments