Life cycle testing of a sealed 24-V, 42-Ah nickel-cadmium aircraftbattery

Extensive research has been conducted in the design and manufacture of very long life sealed maintenance free nickel-cadmium aircraft batteries. This study presents data on a 100% depth of discharge (DOD) life test performed on a nominal capacity 42-Ah battery. The purpose of this study is to validate design concepts, determine the life characteristics of the newly designed sealed Ni-Cd batteries, and develop baseline information on failure rates and mechanisms. The data from this experiment can be used to compare depth of discharge versus battery life with similar tests such as the lower DOD experiments performed on spacecraft batteries. This information is important in the ongoing development of long life batteries and in developing failure models for life prediction     

The status of qualification of a new separator system for advancedaerospace battery cells

A nickel cadmium cell system which utilizes a polypropylene separator impregnated with polybenzimadazole, and which shows promise of providing an aerospace battery with performance equivalent to Super NiCd, and yet is more cost effective, is described. Background information, cell construction information, detailed test program information and data, and status of qualification are given     

The heliosphere

The history and current status of heliospheric physics are outlined very briefly. It is emphasized that the existing Voyager Interstellar Mission should go a long way to answering many of the outstanding questions during the next one or two decades, especially those concerning the nature and structure of the solar wind termination shock.     

Fuzzy logic applications to multisensor-multitarget correlation

A consistent tactical picture requires data fusion technology to combine and propagate information received from diverse objects and usually vague situations. The information may be contained in two types of data; numerical data received from sensor measurements, and linguistic data obtained from human operators and domain experts. In real world situations, the numerical data may be noisy, inconsistent, and incomplete, and the linguistic information is imprecise and vague. To deal with these two types of data simultaneously, fuzzy sets and fuzzy logic provide a methodology to obtain an approximate but consistent tactical picture in a timely manner for very complex or ill-defined engineering problems. A functional paradigm for fuzzy data fusion is presented. It consists of four basic elements: (1) fuzzification of crisp elements, (2) fuzzy knowledge base derived from numerical input/output relations and humans, (3) fuzzy inference mechanism based on a class of fuzzy logic, (4) defuzzification of fuzzy outputs into crisp outputs for use by a plant. For real-time practical systems, the on-line determination of a fuzzy membership function from a given set of crisp inputs is vital. To this end, a methodology for estimating an optimal membership function from crisp input data has been implemented. This is based on the possibility/probability consistency principle as proposed by L.A. Zadeh. A relationship between the fuzzy membership function and the confidence level of statistical input data has been developed and it serves as a design parameter for fuzzification. This technique has been applied to a two-dimensional multisensor-multitarget tracking system. Fuzzy system performance evaluations have been presented. With simulated data in the laboratory environment, the simulation has been performed to evaluate the Mission Avionics Sensor Synergism (MASS) Systems. These results show better performance for the data correlation function using the fuzzy logic techniques.     

Monte Carlo track structure studies of energy deposition and calculation of initial DSB and RBE.

Estimation of exposure due to environmental and other sources of radiations of high-LET and low-LET is of interest in radiobiology and radiation protection for risk assessment. To account for the differences in effectiveness of different types of radiations various parameters have been used. However, the relative inadequacy of the commonly used parameters, including dose, fluence, linear energy transfer, lineal energy, specific energy and quality factor, has been made manifest by the biological importance of the microscopic track structure and primary modes of interaction. Monte Carlo track structure simulations have been used to calculate the frequency of energy deposition by radiations of high- and low-LET in target sizes similar to DNA and higher order genomic structure. Tracks of monoenergetic heavy ions and electrons were constructed by following the molecular interaction-by-interaction histories of the particles down to 10 eV. Subsequently, geometrical models of these assumed biological targets were randomly exposed to the radiation tracks and the frequency of energy depositions obtained were normalized to unit dose in unit density liquid water (l0(3) kg m-3). From these data and a more sophisticated model of the DNA, absolute yields of both single- and double-strand breaks expressed in number of breaks per dalton per Gray were obtained and compared with the measured yields. The relative biological effectiveness (RBE) for energy depositions in cylindrical targets has been calculated using 100 keV electrons as the reference radiation assuming the electron track-ends contribution is similar to that in 250 kV X-ray or Co60 gamma-ray irradiations.     

Ambiguity resolution of multiple targets using pulse-Dopplerwaveforms

To cancel clutter, both medium-PRF waveforms which are ambiguous in both range and Doppler and high-PRF waveforms which are ambiguous in range but unambiguous in ambiguities, a previous paper has shown that superior results for a single target can be achieved by using a clustering algorithm. Here, the problem of multiple targets is considered. A maximum likelihood (ML) technique which incorporates the clustering algorithm is developed for the multiple target problem. Simulation results show that four targets which have the same speed but are at different ranges can be resolved by using a medium-PRF waveform and employing the ML resolution technique     

Electron density models for the lower ionosphere

Probably the only reliable method of checking an electron density model below 70 km is to calculate from it what would be obtained by VLF or LF propagation over certain paths, and to compare the results with actual observations. This has been done for the IRI at various frequencies from 16 to 70 kHz; the results agree in places but differ substantially elsewhere. Previous models described by the author give satisfactory results and it is suggested that certain features of them might be incorporated with advantage in the IRI. In particular, it is impossible to get agreement with VLF propagation in all seasons by means of a model varying only with solar zenith angle, such as the IRI from 50–90 km.     

Calibration techniques for magnetometers implementing on-board de-spinning algorithms

The Fluxgate Magnetometer experiments on-board the European Space Agency’s four spacecraft Cluster Mission have the capability to store sampled magnetic field vectors in the instrument memory, either as a full resolution ‘event capture’ or as spin-resolution vectors transformed into a non-spinning co-ordinate system (de-spun). The latter capability has ensured a dataset is available which extends the partial orbital coverage achieved during nominal operations in the first years of operation. The on-board de-spin is achieved using a Walsh function with Haar coefficients and allows for up to 27 h additional data per non-coverage interval. A number of commissioning orbits were used to verify the accuracy of data collected by the de-spin mode, whereby individual spacecraft were operated separately in a number of standard normal sampling and de-spin mode combinations. Up to the present time, this data has not been available to the Cluster community. We present results here comparing the performance of the on-board de-spin algorithm versus the normal sampling modes over a number of boundary layer crossings, describe the techniques used for calibration and timeline recovery, and outline the context in which the data may be usable in future studies.     

Results from the ESA SREM monitors and comparison with existing radiation belt models

The Standard Radiation Environment Monitor (SREM) is a simple particle detector developed for wide application on ESA satellites. It measures high-energy protons and electrons of the space environment with a 20° angular resolution and limited spectral information. Of the ten SREMs that have been manufactured, four have so far flown. The first model on STRV-1c functioned well until an early spacecraft failure. The other three are on-board, the ESA spacecraft INTEGRAL, ROSETTA and PROBA-1. Another model is flying on GIOVE-B, launched in April 2008 with three L-2 science missions to follow: both Herschel and Planck in 2008, and GAIA in 2011). The diverse orbits of these spacecraft and the common calibration of the monitors provides a unique dataset covering a wide range of B-L* space, providing a direct comparison of the radiation levels in the belts at different locations, and the effects of geomagnetic shielding. Data from the PROBA/SREM and INTEGRAL/IREM are compared with existing radiation belt models.     

Light microscopic analysis of the gravireceptor in Xenopus larvae developed in hypogravity.

The paper describes an investigation of the influence of gravity on the early differentiation of gravity receptors in Xenopus embryos and larvae. There is evidence that the expression of crystals in the saccus endolymphaticus was statistically greater when the embryos developed in near weightlessness (hypogravity) than on earth. The function of these crystals is unknown but they may contribute to the functioning of the vestibular apparatus.