Spaceborne P-Band MIMO SAR for Planetary Applications

The Space Exploration Synthetic Aperture Radar (SESAR) is an advanced P-band beamforming radar instrument concept to enable a new class of observations suitable to meet Decadal Survey science goals for planetary exploration. The radar operates at full polarimetry and fine (meter scale) resolution, and achieves beam agility through programmable waveform generation and digital beamforming. The radar architecture employs a novel low power, lightweight design approach to meet stringent planetary instrument requirements. This instrument concept has the potential to provide unprecedented surface and near-subsurface measurements applicable to multiple Decadal Survey Science Goals

The association between board characteristics and the risk-adjusted return of South African companies

PURPOSE : Regulatory documents and the literature recommend individuals with various characteristics to be included on a board, which should improve the efficiency of the board and promote company performance. Stakeholders have different expectations from a company, for which the literature holds the board accountable. Shareholders, for example, want superior returns, while government requires the implementation of transformation initiatives, especially in South Africa. It will therefore be valuable to several interested parties to know which board characteristics are likely to promote their objectives. DESIGN/METHODOLOGY/APPROACH : Binary logistic regression is used to analyse the relationship between various board characteristics and the risk-adjusted performance of a company. The dataset comprised 170 companies, from the 13 largest sectors/subsectors of the Johannesburg Stock Exchange for the period 2009 to 2015. FINDINGS : Percentage female (negative), chief executive officer remuneration (negative), chairman remuneration (positive) and non-executive director remuneration (positive) and the payment gap (positive) showed statistically significant relationships with the odds that a company is categorised as a top performer based on its risk-adjusted return. PRACTICAL IMPLICATIONS : The findings inform various parties whether the benefits ascribed to the various board characteristics, by the literature and regulations, are actually obtained. ORIGINALITY/VALUE : The study moved away from the practice of looking for linearity in corporate relationships and expanded the list of board characteristics reviewed. It used a risk-adjusted performance measure, introduced innovative diversity measures, and focussed on South Africa.https://www.palgrave.com/gp/journal/413102021-10-14hj2021Financial Managemen

Beamforming P-Band Synthetic Aperture Radar for Planetary Applications

The Space Exploration Synthetic Aperture Radar (SESAR) is an advanced P-band beamforming radar instrument concept to enable a new class of observations suitable to meet multiple Decadal Survey science goals for planetary exploration. The radar is capable of providing unprecedented surface and near subsurface measurements at full polarimetry and fine (meter scale) resolution, and achieves beam agility through programmable waveform generation and digital beamforming. The radars highly flexible modular architecture employs a novel low power, lightweight design approach to meet stringent planetary instrument requirements, all while minimizing cost and development time

Signals of Opportunity - Airborne Demonstrator (SoOP-AD): Instrument Overview, Performance During First Flights and Future Instrument Concept

The Signals of Opportunity Airborne Demonstrator (SoOp-AD) was developed as part of the NASA InstrumentIncubator Program (IIP) with the goal of maturing the use of SoOp from existing communication satellites in geostationaryorbit, operating within the heavily used P-band (under 500 MHz) spectrum for soil moisture observations. P-band offers the benefit of roughly five (5) times deeper soil penetration compared to conventional L-band methods. SoOp-AD operates in a bi-static radar configuration, and only requires reception of direct and scattered signals from the source satellite. In this paper we present an overview of the SoOp-AD instrument architecture, signal processing, internal calibration approach and preliminary results from flights over the Little Washita watershed in Oklahoma, USA. Finally, future steps towards a U-class ("cubesat") instrument concept based upon experience with the airborne demonstrator are presented

The Ecosystems SAR (EcoSAR) an Airborne P-band Polarimetric InSAR for the Measurement of Vegetation Structure, Biomass and Permafrost

EcoSAR is a new synthetic aperture radar (SAR) instrument being developed at the NASA/ Goddard Space Flight Center (GSFC) for the polarimetric and interferometric measurements of ecosystem structure and biomass. The instrument uses a phased-array beamforming architecture and supports full polarimetric measurements and single pass interferometry. This Instrument development is part of NASA's Earth Science Technology Office Instrument Incubator Program (ESTO IIP)

The Radio Frequency Environment at 240-270 MHz with Application to Signal-of-Opportunity Remote Sensing

Low frequency observations are desired for soil moisture and biomass remote sensing. Long wavelengths are needed to penetrate vegetation and Earths land surface. In addition to the technical challenges of developing Earth observing spaceflight instruments operating at low frequencies, the radio frequency spectrum allocated to remote sensing is limited. Signal-of-opportunity remote sensing offers the chance to use existing signals exploiting their allocated spectrum to make Earth science measurements. We have made observations of the radio frequency environment around 240-270 MHz and discuss properties of desired and undesired signals

Sensitization behaviour of 11-12% Cr AISI 409 stainless steel during low heat input welding

The study comprised of the investigation into the sensitization characteristics of AISI 409 titanium stabilized ferritic stainless steel during low heat input welding. AISI 409 is a fully ferritic stainless steel used in catalytic converters and tubing for automotive exhaust systems due to the supposition that sensitization does not occur during low heat input welding. Two plates of 2 and 4 mm were tested for sensitization during low heat input welding. The study confirmed that chromium carbide (M23C6) precipitation occurs on the grain boundaries in the heat-affected zone with consequent depletion of Cr adjacent to the grain boundaries during welding. In the 2 mm plate sensitization occurred in the heat input range of 0.1 kJ/mm to above 0.25 kJ/mm and in the 4 mm plate sensitization occurred in the heat input range of 0.2 to 0.9 kJ/mm. Ti stabilization is ineffective at the heat inputs used in this investigation due to the rapid cooling rate through the temperature region where TiC precipitates. The presence of N was found to be detrimental since it consumes Ti on cooling, forming TiN, effectively lowering the amount of Ti available for TiC formation during rapid cooling after welding. Annealing for 5 minutes at 725°C does not improve the sensitization characteristics of the welded plate. There is a linear increase in grain size as heat input increases. The resistance to pitting corrosion decreases in the sensitized, welded plate in the heat-affected zone adjacent to the fusion line of welding

The three-dimensional far-fields of antennas from probe corrected cylindrical near-field measurements

Thesis (M.Ing) -- University of Stellenbosch, 1986.Full text to be digitised and attached to bibliographic record

The computation of electromagnetic fields at non-asymptotic distances from an antenna using cylindrical near-field measurements

Dissertation (Ph. D.) -- University of Stellenbosch, 1992.One copy microfiche.Full text to be digitised and attached to bibliographic record