Synthetic aperture radar imaging systems

This paper presents profiles of 12 airborne and spaceborne Synthetic Aperture Radar (SAR) imaging systems. This information is intended to help potential users evaluate the systems for specific applications. The systems profiled in this article can be used for commercial purposes; some have been built specifically for commercial use while others also serve as science and research tools, Both domestic and foreign systems designed for government agencies and private industry are profiled. Nine of these systems are currently operational; two systems are scheduled to begin service in the near future. A third system is no longer active, but archive data are commercially available     

Magnetic propulsion systems

Magnetic propulsion systems are based on the direct interaction of the vehicle's own magnetic field with the natural magnetic field, particularly the geomagnetic one, without using jet propulsion. Three such systems are reviewed in the order of their feasibility of automatic control over the thrust force vector. One of these magnetic propulsion systems permits partial control and is competitive with the electromagnetic or plasma rocket orbital microthrusters. The importance of the other two promising systems is to establish the main principles of magnetic propulsion. Their development depends on progress in solid-state physics. One of them may be able to have total control over the direction and modulus of the electrodynamic thrust force vector.     

Reconfigurable COTS test systems

Automatic Test Equipment (ATE) systems are used to qualify, accept, and troubleshoot electronic products. ATE systems may be in the form of large general-purpose systems that can test a wide variety of products or the more commonly used custom, turnkey systems that are designed for specific test application(s) and requirements. Turnkey ATE systems are labor-intensive; as a result, even a relatively simple turnkey tester is costly and may take months (or even years) to develop, integrate, and deploy. The main reason for this aspect of turnkey ATE systems is that even though the instrumentation may be off-the-shelf components, most everything else is custom and requires design, development, extensive debug and integration. Time and again, systems integrators have tried to find a solution that would combine the cost effectiveness of COTS systems with the flexibility of custom ATE. This paper suggests a solution to this problem and that it is feasible to combine COTS testers with custom requirements. This solution, called CreATE, provides a flexible architecture using COTS components (including instruments, cabling and interfacing products)     

What is systems engineering?

There are probably more definitions of “Systems Engineering” than there are AESS members. In its simplest form systems engineering is the design of the whole as opposed to the design of the parts. The vast number, complexity and diversity of elements can overwhelm and degrade system performance and reliability. Embedded processing and software can be both a boon and a bane. A systems engineer analyzes and optimizes an ensemble of elements that relate to the flow of energy, mass and communications into a design that performs the desired function. “Systems engineering” is used herein to cover a very broad spectrum of processes and controls to engineer a product at the many levels required to satisfy all aspects of the original requirement. Our definition is not intended to either include or exclude systems engineering and integration as used in the computer field. In any case, systems engineering is the application of solid engineering principles to design and develop a large enterprise within cost and schedule to satisfy the needs of the ultimate user. It involves conceptualization, design, development, test, implementation, approval/certification and operation (including human factors) of a system. In essence, systems engineering is a problem-solving discipline for the modern world     

Air traffic control systems

The following topics are dealt with: ATC evolution; navigation and landing; navigation aids; surveillance and weather; automation systems     

Interface and usability assessment of imaging systems

This paper discusses a plan for collecting critical information about the interface, usability, and the efficiency and effectiveness of two imaging systems: Rapiscan's Secure 1000 and American Science & Engineering's Body Search; both systems use backscatter technology.     

Geomagnetic induction effects in ground-based systems

Plasma physics processes, whose ultimate origin is the Sun, exist in the Earth's magnetosphere and ionosphere and can produce effects which are detrimental to the operation of technological systems associated with long conductors deployed on the Earth's surface. Geomagnetic fluctuations produced by such plasma processes can cause disturbances and disruptions in cable communication systems, electrical power distribution systems, and long pipelines. This paper briefly addresses these three topics with illustrative examples of some measured effects from each topic area.     

A visionary look at aviation surveillance systems

The FAA's future aviation surveillance systems fall into four categories: Automatic Dependent Surveillance (ADS) will be used in the oceanic environment; ADS-Broadcast (ADS-B) will be used in the domestic en route environment; ADS-B will be used with a secondary radar backup in the terminal area; and ADS-B will be used with primary radar backup within the Airport Surface Traffic Automation (ASTA) system on the airport's surface environment. Two other systems introduced in this paper are Cockpit Display of Traffic Information (CDTI) and Traffic Advisory and Collision Avoidance System (TCAS). All these systems will use navigational signals emitted by the Global Positioning System (GPS) constellation of satellites     

Micro-power Amtec systems

There are several terrestrial applications for energy conversion systems with electrical outputs of a few volts in the power range from hundreds of milliwatts to a few watts. Potential applications include: power for instrumentation, communication and device actuation in severe or harsh environments, as well as a variety of low duty cycle monitoring tasks for the military. For cost and/or packaging reasons, some of these applications are severely heat source limited. In this paper we describe the development and performance of AMTEC systems capable of producing 0.3 to 0.5 watts from a radioisotope heat source limited to a total thermal output of less than 4 watts, The approach utilizes a new “chimney cell” design and a thermal insulation system consisting of a specialized multi-layer insulation (MLI) package in combination with fibrous insulation. The cell operates at 0.4 W_c to over 0.5 W_c with an input surface temperature of 700°C. Measurements of the thermal performance of a readily manufactured MLI package indicate that operation at these temperatures will be achievable with a total heat input of ~4 W_th     

Evolution into contact of the low-mass close binary systems

We investigated the effect of mass accretion on the secondary components in close binomy systems (M _total ≤ 2.5 M _⊙ M _2,0 ≤ 0.75 M _⊙) exchanging mass in the case A. The evolution of the low-mass close binary systems (M _total ≤ 2.5 M _⊙) exchanging the mass in the case A depends on the three main factors:

-the initial mass ratio (q ₀ = M _2,0/M _1,0), which determines the rate of mass transfer between components;

-the inital mass of the secondary component (M _2,0) and

-the effectiveness of the heating of the photosphere of the secondary component, by infalling matter.

The second factor allows to divide all systems into two essentially different groups:

1. systems in which the secondary component is a star with a radiative envelope, or with a thin convection zone in the uppermost layers;
2. and systems in which secondary component has a thick convective envelope or is fully convective.

The systems from the first group evolve into contact in a characteristic time scale 10⁵ – 10⁷ years, and reach contact after transfering of 0.03 – 0.3 M _⊙. The mass exchange proceeds only in a thermal time scale. For the systems from the group b the effectiveness of the heating of the stellar surface is the most important. In the case when the entropy of the newly accreted matter is the same as the surface entropy of the secondary, a convective star should shrink upon accretion. Then contact binaries are not formed. In the case when the entropy of the infalling matter is greater then that on the surface, the reaction of the secondary is different. The radius of the secondary component grows rapidly in response to accretion, and the systems reaches contact after the 10³ – 3 10⁶ years, and after transfer of 0.002 – 0.2. M _⊙. The reaction of the secondary is determined by the formation of the temperature inversion layer below the stellar surface. Full references in: Sarna, M.J. and Fedorova, A.V. (1988) “Evolutionary status of W UMa-type Binaries — Evolution into contact”, Astron. Astrophys., in press.     

Two centuries of study of Algol systems

The periodicity of the light variation of Algol, discovered just over 200 years ago, may be regarded as the beginning of the study of eclipsing binary systems, especially those of the Algol type. Such studies, however, gained no real momentum until Vogel, 100 years ago, demonstrated by spectroscopy that the binary hypothesis of Algol's light changes is, in its essentials, correct. Three elements were needed to give us our modern notions of evolution by mass-transfer, namely: (i) results of combined analysis of light-curves and velocity-curves, (ii) evidence of circumstellar matter within binary systems and (iii) the notion that at least one component of an Algol system was near the limit of dynamical stability. All three entered the literature within about a decade, approximately halfway through the second century of eclipsing-binary studies; but it is the computational and instrumental developments of the last 25 years that have made real progress possible. We still lack commensurate theoretical developments, and the whole question of the contribution of Algol systems to the development of the Galaxy has barely been considered.     

Scaling of advanced power systems

Parts of a study conducted to examine state-of-the-art power systems applicable to future military spacecraft are summarized. The study focused on burst-mode megawatt-class CW power, such as might be applied to SDIO directed energy systems, but lower-power, continuous-duty subsystems were included in less detail. A set of simple mass and volume algorithms has been developed to approximate several prime systems, and these were incorporated into a Lotus 1-2-3 spreadsheet. Among the power subsystems included in that study were primary batteries, alkaline primary fuel cells, and combustion turbogenerators. These systems, which are the most likely candidates for mobile battlefield power, are described     

Maglev systems development status

The current status and future potential of Maglev systems is reviewed. Modes of noncontact suspension and propulsion are described, and prototype systems and design concepts are indicated. A number of existing systems are described in more detail     

Expert systems in engineering

An overview of expert systems development and some engineering applications are presented. The characteristics of expert systems are first described. Three applications of expert systems, in factory scheduling, maintenance, and electronic testing, are briefly examined. Their advantages and disadvantages are discussed     

Radioisotope powered AMTEC systems

Alkali Metal Thermal to Electric Converter (AMTEC) systems are being developed for high performance spacecraft power systems, including small, General Purpose Heat Source (GPHS) powered systems. Several design concepts have been evaluated for the power range from 75 W to 1 kW. The specific power for these concepts has been found to be as high as 18-20 W/kg and 22 kW/m³. The projected area, including radiators, has been as low as 0.4 m²/kW. AMTEC power systems are extremely attractive, relative to other current and projected power systems, because AMTEC offers high power density, low projected area, and low volume. Two AMTEC cell design types have been identified. A single-tube cell is already under development and a multi-tube cell design, to provide additional power system gains, has undergone proof-of-principle testing. Solar powered AMTEC (SAMTEC) systems are also being developed, and numerous terrestrial applications have been identified for which the same basic AMTEC cells being developed for radioisotope systems are also suitable     

Short-range radio navigation systems: current status and prospects

The problems of the development of short-range navigation aids as integrated multifunctional systems for the near future while implementing them in poorly equipped regions, ice-breaker fleets, and on remote oil platforms are discussed. Conclusions are drawn about the reasonability of utilization for those purposes of various modifications of the existing integrated short-range navigation systems. These systems provide highly accurate operation, have a convenient ρ-&thetas; coordinate system, and are capable in some cases of providing the additional functions     

Open architecture-based factory automation systems

This mainly discusses the next generation factory automation systems, i.e., open systems. Along the dimension of open architecture, it discusses some standardized methodologies involving Linux open source operating systems, platform independent programming languages, systematic object-oriented software engineering, web-based information publishing, virtual instrument-based system structure, distributed and embedded real-time systems, etc., and their applications in factory automation systems. The resulting open systems are capable of keeping up with the evolving requirements in the factory automation arena, and it is expected that the strict use of standards would bring benefits to enterprises in the long sight.     

Stochastic stability theory for systems containing intervalmatrices

Known conditions for the stability of stochastic, linear time-varying (LTV) dynamical systems based on Liapunov theory are applied to LTV dynamical systems containing interval matrices; both discrete and continuous time processes are considered. These conditions are sufficient for stability with probability 1 (wp1) and, in the case of discrete time, also necessary for stability in m.s. They lead to a simple, noniterative technique that involves the computation of eigenvalues of matrices whose elements often consist of first- and/or second-order moments. The results are useful in areas such as robust design, feedback control, perturbation analysis, and fault tolerant systems     

Airborne hyperspectral sensor systems

This paper presents brief profiles of 19 airborne hyperspectral sensor systems currently or nearly available for data acquisition. These systems represent various design concepts and innovations in hyperspectral information collection technology. A number of companies now have the ability to acquire data from these systems. As the scientific and commercial communities become aware of hyperspectral imaging data acquisition opportunities, more applications for this type of data will be investigated and implemented     

Two centuries of study of Algol systems

The periodicity of the light variation of Algol, discovered just over 200 years ago, may be regarded as the beginning of the study of eclipsing binary systems, especially those of the Algol type. Such studies, however, gained no real momentum until Vogel, 100 years ago, demonstrated by spectroscopy that the binary hypothesis of Algol's light changes is, in its essentials, correct. Three elements were needed to give us our modern notions of evolution by mass-transfer, namely: (i) results of combined analysis of light-curves and velocity-curves, (ii) evidence of circumstellar matter within binary systems and (iii) the notion that at least one component of an Algol system was near the limit of dynamical stability. All three entered the literature within about a decade, approximately halfway through the second century of eclipsing-binary studies; but it is the computational and instrumental developments of the last 25 years that have made real progress possible. We still lack commensurate theoretical developments, and the whole question of the contribution of Algol systems to the development of the Galaxy has barely been considered.