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231.
Viswanath H.C. Jones R.A. 《IEEE transactions on aerospace and electronic systems》1993,29(4):1195-1203
The anomaly in the displacement estimates obtained from a low-level Kalman-based average displacement estimator is used to detect multiple targets in a forward-looking infrared (FLIR) scene. The displacement estimates originating from the targets could be associated with the detected multiple targets and an updated estimated position of the target could be obtained. This procedure could be repeated for all targets in the scene to obtain multitarget tracking. The behavior of the expected value of the displacement estimates as a function of the number of iterations is investigated. The behavior of the displacement error covariance matrix and the Kalman gain matrix are discussed as functions of the number of iterations 相似文献
232.
Multiposition alignment of strapdown inertial navigation system 总被引:3,自引:0,他引:3
Lee J.G. Park C.G. Park H.W. 《IEEE transactions on aerospace and electronic systems》1993,29(4):1323-1328
The authors demonstrate that the stationary alignment of strapdown inertial navigation system (SDINS) can be improved by employing the multiposition/technique. Using an observability analysis, it is shown that an optimal two-position alignment not only satisfies complete observability conditions but also minimizes alignment errors. This is done by analytic rank testing of the stripped observability matrix and numerical calculation of the error covariance. It is also shown that an optimal three-position alignment accelerates the convergence of the alignment error compared with two-position alignment 相似文献
233.
An optical design study for a next generation infrared space telescope has been performed. The concept is that of a passively cooled telescope of minium aperture 2.5 metre with an F/1.2 primary and wavelength coverage from = 2 to at least 40 m, and possibly to 100 m. Compactness, low thermal emission from the optics and structure, diffraction limited imaging at = 2 m, and sensitivity to misalignment aberrations and manufacturing errors were the main considerations for this study. Ray tracing results are presented showing the characteristics of the various designs considered. A preliminary investigation of stray light properties is also given. Special emphasis has been placed on the testing of such a fast primary, and optical systems using a lateral shearing interferometer are described for testing both the primary and the primary/secondary combination. 相似文献
234.
235.
The Galileo Probe Atmosphere Structure Instrument will make in-situ measurements of the temperature and pressure profiles of the atmosphere of Jupiter, starting at about 10-10 bar level, when the Probe enters the upper atmosphere at a velocity of 48 km s-1, and continuing through its parachute descent to the 16 bar level. The data should make possible a number of inferences relative to atmospheric and cloud physical processes, cloud location and internal state, and dynamics of the atmosphere. For example, atmospheric stability should be defined, from which the convective or stratified nature of the atmosphere at levels surveyed should be determined and characterized, as well as the presence of turbulence and/or gravity waves. Because this is a rare opportunity, sensors have been selected and evaluated with great care, making use of prior experience at Mars and Venus, but with an eye to special problems which could arise in the Jupiter environment. The temperature sensors are similar to those used on Pioneer Venus; pressure sensors are similar to those used in the Atmosphere Structure Experiment during descent of the Viking Landers (and by the Meteorology Experiment after landing on the surface); the accelerometers are a miniaturized version of the Viking accelerometers. The microprocessor controlled experiment electronics serve multiple functions, including the sequencing of experiment operation in three modes and performing some on-board data processing and data compression. 相似文献
236.
Design for validation 总被引:2,自引:0,他引:2
An approach is outlined for the development of ultrareliable avionics for civil air transports using a design-for-validation philosophy that includes rigorous application of formal methods. The basic concept of the methodology is introduced, and the role of formal methods is explored. The impact of the design-for-validation philosophy on the system design process is then demonstrated by two simple examples. More details about the design-for-validation methodology are then given 相似文献
237.
CFAR data fusion center with inhomogeneous receivers 总被引:1,自引:0,他引:1
Elias-Fuste A.R. Broquetas-Ibars A. Antequera J.P. Yuste J.C.M. 《IEEE transactions on aerospace and electronic systems》1992,28(1):276-285
Detection systems with distributed sensors and data fusion are increasingly used by surveillance systems. A system formed by N inhomogeneous constant false alarm rate (CFAR) detectors (cell-averaging (CA) and ordered statistic (OS) CFAR detectors) is studied. A recursive formulation of an algorithm that permits a fixed level of false alarms in the data fusion center is presented, to set the optimum individual threshold levels in the CFAR receivers and the optimum `K out of N ' decision rule in order to maximize the total probability of detection. The algorithm also considers receivers of different quality or with different communication channel qualities connecting them with the fusion center. This procedure has been applied to several hypothetical networks with distributed CA-CFAR and OS-CFAR receivers and for Rayleigh targets and interference, and it was seen that in general the fusion decision OR rule is not always the best 相似文献
238.
A data path consists of memory elements (i.e., registers), data operators (i.e. ALUs) and interconnection units (i.e. buses) to control the data transfers in the digital system. Many approaches to hardware allocation for data path synthesis have been proposed in the literature; however, only single-port memory is considered for register allocation and no efficient synthesis approach for multiport memory synthesis. A novel design methodology for data path synthesis using multiport memories is proposed which can be applied to hardware allocation algorithms or to already synthesized data path as a postprocessor to achieve a better design. Illustrations of applying this method to different synthesis examples are presented. Results and improvements over previous techniques are demonstrated. Experiments on benchmarks show very promising results 相似文献
239.
A. Aboudan G. Colombatti C. Bettanini F. Ferri S. Lewis B. Van Hove O. Karatekin S. Debei 《Space Science Reviews》2018,214(5):97
On 19th October 2016 Schiaparelli module of the ExoMars 2016 mission flew through the Mars atmosphere. After successful entry and descent under parachute, the module failed the last part of the descent and crashed on the Mars surface. Nevertheless the data transmitted in real-time by Schiaparelli during the entry and descent, together with the entry state vector as initial condition, have been used to reconstruct both the trajectory and the profiles of atmospheric density, pressure and temperature along the traversed path.The available data-set is only a small sub-set of the whole data acquired by Schiaparelli, with a limited data rate (8 kbps) and a large gap during the entry because of the plasma blackout on the communications.This paper presents the work done by the AMELIA (Atmospheric Mars Entry and Landing Investigations and Analysis) team in the exploitation of the available inertial and radar data. First a reference trajectory is derived by direct integration of the inertial measurements and a strategy to overcome the entry data gap is proposed. First-order covariance analysis is used to estimate the uncertainties on all the derived parameters. Then a refined trajectory is computed incorporating the measurements provided by the on-board radar altimeter.The derived trajectory is consistent with the events reported in the telemetry and also with the impact point identified on the high-resolution images of the landing site.Finally, atmospheric profiles are computed tacking into account the aerodynamic properties of the module. Derived profiles result in good agreement with both atmospheric models and available remote sensing observations. 相似文献
240.
Messenger S. Stadermann F.J. Floss C. Nittler L.R. Mukhopadhyay S. 《Space Science Reviews》2003,106(1-4):155-172
Interplanetary dust particles collected in the stratosphere frequently exhibit enrichments in deuterium (D) and 15N relative to terrestrial materials. These effects are most likely due to the preservation of presolar interstellar materials.
While the elevated D/H ratios probably resulted from mass fractionation during chemical reactions at very low < 100 K temperatures,
the origin of the N isotopic anomalies remains unresolved. The bulk of the N-bearing material may have obtained its isotopic
signatures from low temperature chemistry, but a nucleosynthetic origin is also possible.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献