Design for testability for future digital avionics systems

The authors describe an integrated testing approach called the Maintenance and Diagnostic System (MADS), which was developed for digital avionics systems using VHSIC and semicustom devices. Mission/operational requirements dictate high availability with capability to detect 98% of all faults and isolate 90% of these faults to a line replacement module (LRM) or 95% of the faults to two LRMs. MADS achieves these goals by defining a module maintenance node (MMN) chip set for each LRM in the system and the design for testability concepts for hardware. The MMN aids parallel, high-speed testing of LRMs, isolating the fault(s) to a module/chip level while incurring less than 10% overhead. It uses the concepts of scan set design, pseudorandom test vector generation, output response compression, and separate scan set loops to test the SSI-MSI logic on the LRM. It also stores interim test results and run-time fault information to isolate the hard-to-reproduce failures and performs verification of interchip and intermodule wiring     

Computational Precision Requirements for Optimal Weights in Adaptive Processing

The required accuracy for computing the estimated optimum weights of an adaptive processor has been analyzed by investigating the effects of errors in computing the inverse matrix. It is shown that the required precision depends upon the matrix. An equation for the general case is derived. Several special cases are considered in detail. It is shown that the case of a single interference source requires the highest precision. The least stressing case is identifi'ed and compared to the worst case. The requirements for a "typical" case are also considered. A comparison of the requirements for the covariance matrix estimation technique and for adaptive weight implementation using gradient descent techniques is given. It is shown that there is a dichotomy in that cases that do not stress one technique tend to stress the other.     

The Circular Synthetic Radar

A new type of synthetic radar, the circular synthetic radar, uses a simple interferometer whose elements are mounted at the ends of a horizontal boom rotating about a vertical mast. Pulses are radiated alternately ?in-phase? and in ?phase-quadrature.? The returning echoes are also detected incoherently, both ?in-phase? and in ?phase-quadrature.? The four distinct outputs are fed into an on-line computer which, after a Fourier analysis, synthesizes a mapping function of the azimuthal distribution of targets.     

Activity Planning for the Space Station

This paper presents an overview of the identification and selection process of experiments and payloads for manned space flight missions, emphasizing the scope and magnitude of the problem of doing activity planning and the need for a methodology to assure timely flight and appropriate spacecraft design. Conclusions and results derived from the past several years are presented together with an analysis of the current procedure for defining activity for the space station.     

Experiments with injection of powerful plasma jet into the ionosphere

This paper describes two rocket experiments “Aelita” with high power lithium plasma injection. The results of onboard magnetometer, massspectrometer, photometer, plasma, corpuscular and ground radar measurements are given. Dynamics and structure of plasma formation are discussed.     

Improvement of Automatic Landing Through the Use of a Space Diversity ILS Receiving System

A space diversity method of receiving and processing ILS localizer information has been developed and flight tested. Multiple lateral ly separated antennas are used which sense the ILS signal on and around the approach path. Combining these signals suppresses ILS beam distortion produced by multipath signal interference and provides much improved guidance information to the landing aircraft control system.     

Possibilities of investigation of X-ray sources on archival plates

The use of archival plates for investigations on X-ray sources is discussed and several examples of results are given.     

A Matched-Filter Pulse-Compression System Using a Nonlinear FM Waveform

The realization of a rectangular pulse-compression waveform having low time sidelobes and zero mismatch loss due to spectral weighting is discussed. The theoretical aspects of the design of such a waveform are presented with particular reference to frequency modulated, rectangular pulses. The design and performance of a matched-filter pulse-compression system having essentially zero mismatch loss are presented. The system discussed has a time-bandwidth product of 22 and time sidelobes suppressed at least 27 dB; the measured mismatch loss is 0.1 dB. The difficulty of achieving the required nonlinear time delay dispersion is overcome by synthesizing the dispersive network as a cascade of all-pass networks.     

Prolonged weightlessness and calcium loss in man

Data have been accumulated from a series of studies in which men have been subjected to weightlessness in orbital space flight for periods of up to 12 weeks. These data are used to predict the long term consequences of weightlessness upon the skeletal system. Space flight induced a loss of calcium which accelerated exponentially from about 50 mg/d at the end of 1 week to approx. 300 mg/d at the end of 12 weeks. The hypercalciuria reached a constant level within 4 weeks while fecal calcium losses continued to increase throughout the period of exposure. This apparent diminution of gastrointestinal absorptive efficiency was accompanied by a slight decline in the plasma level of parathyroid hormone and a slight elevation in the plasma level of calcium and phosphorus. Although losses in mineral from the calcaneus were closely correlated with the calcium imbalance, no changes were detected in the mineral mass of the ulna and radius. From the data presented it is concluded that the process of demineralization observed in space flight is more severe than would be predicted on the basis of observations in immobilized, bed rested, or paralyzed subjects. It is, moreover, suggested that the process may not be totally reversible.     

Altitude Damping of Space-Stable Inertial Navigation Systems

In order to stabilize the altitude calculation in an inertial navigation system, an altimeter is commonly used. In a conventional local-level mechanization, this is generally accomplished by correcting the vertical channel integrators with the difference between the inertial system and altimeter indication of vertical position. However, in a space-stable system the procedure is not as clear since a vertical channel is not physically present. Three altitude damping mechanizations for a space-stable inertial navigation system are proposed. The equivalent local-level mechanizations are then found by comparing error propagation equations in a common coordinate frame.