Search

Aircraft observations of wind and temperature collected by airport surveillance radars [Mode-S Enhanced Surveillance (Mode-S EHS)] were assimilated in the Consortium for Small-Scale Modeling Kilometre-scale Ensemble Data Assimilation (COSMO-KENDA), which couples an ensemble Kalman filter to a 40-member ensemble of the convection permitting COSMO-DE model. The number of observing aircrafts in Mode-S EHS was about 15 times larger than in the AMDAR system. In the comparison of both aircraft observation systems, a similar observation error standard deviation was diagnosed for wind. For temperature, a larger error was diagnosed for Mode-S EHS. With the high density of Mode-S EHS observations, a reduction of temperature and wind error in forecasts of 1 and 3 hours was found mainly in the flight level and less near the surface. The amount of Mode-S EHS data was reduced by random thinning to test the effect of a varying observation density. With the current data assimilation setup, a saturation of the forecast error reduction was apparent when more than 50% of the Mode-S EHS data were assimilated. Forecast kinetic energy spectra indicated that the reduction in error is related to analysis updates on all scales resolved by COSMO-DE. [ABSTRACT FROM AUTHOR]

Modelling long-range Loran-C signal propagation numerically is challenging because of its extremely high computational cost. Other analytical/semi-analytical methods are not accurate enough because of unavoidable approximations. In this study, the authors put forward a solution using the adaptive moving window finite-difference time-domain (FDTD) method to compute unified device architecture parallel computing techniques. The moving velocity of the window is dependent upon the wave speed adaptively. To achieve the adaptive moving window technique, the original Loran-C signal is truncated first. A further method employed to extract the electric field amplitude and phase is proposed. The electric field amplitude and phase data of each mesh in the computational space are synchronously obtained from the spatial domain as the FDTD updates, without additional storage cost and post processing in the time domain. With all these efforts, a 400 km propagation path was simulated successfully within 22 min. Measurement results between Jinxian and Shangrao in Jiangxi Province, China were taken to validate the numerical approach. [ABSTRACT FROM AUTHOR]

This paper presents the sharing analysis of the 694-790 MHz frequency band for Mobile services IMT and Aeronautical radio-navigation services (ARNS) using SEAMCAT (established by CEPT) software based on the statistical simulation (Monte-Carlo) method. In 2012 the World Radiocommunication Conference (WRC-12) decided to allocate the 694-790 MHz frequency band (the so-called 700 MHz band) to mobile services IMT (excluding aeronautical mobile) after WRC-15 conference. But this agreement raises electromagnetic compatibility problems, which should be solved until WRC-15 [1]. This study was carried out in two phases: first applying theoretical analysis, then statistical Monte-Carlo simulations with SEAMCAT software tool in order to verify results obtained in theoretical approach. Analytical calculations shows that the required protection distances between ARNS stations and the MS base stations are 132 km. The obtained results from SEAMCAT simulations indicate that separation distance should be above 100 km. These results illustrate that the systems are not electromagnetically compatible. The possible mitigation technic could be antenna pattern correction. [ABSTRACT FROM AUTHOR]

ABSTRACT We present a method to improve the integrity error bound in Advanced RAIM by optimizing the position solution and the integrity allocation simultaneously. Since the reduction in the error bound is achieved by degrading the position accuracy under nominal conditions, the method takes into account the accuracy constraint in the optimization. Advanced RAIM may have to consider a larger number of satellites and increased probabilities of fault, so this method is designed to accept a wide variety of threat models (in particular multiple faults). The search of the optimal coefficients is cast as a convex optimization problem with constraints. The solution is obtained iteratively, and the convexity of the problem guarantees a very fast convergence. The algorithm is evaluated by comparing its performance with algorithms where the position solution is not optimized, and showing how it could help achieve worldwide coverage of vertical guidance (LPV-200). Copyright © 2013 Institute of Navigation [ABSTRACT FROM AUTHOR]

The paper considers how a spacecraft can be put into orbit around a small asteroid to function as its artificial moon. We study the general behavior of perturbations that affect the current coordinates of an orbiting spacecraft and estimate the perturbations caused by the main perturbing factors, i.e., (1) the irregular shape of an asteroid and (2) celestial bodies of the Solar System. With specific orbital parameters, a long-term targeted operation of a spacecraft can be actualized in a mission to the asteroid Apophis where the spacecraft will carry a radio beacon transponder. [ABSTRACT FROM AUTHOR]

The article offers information on gunshot detection systems. The entry notes that a gunshot detection network consists of sensors and computers that can identify the location of a shot, the weapon caliber and the number of rounds fired from a gun. In relation to this, gunshot detection originated from the Loran navigation system used in World War II which used pairs of radio stations that exchanged synchronized pulses to determine the relative position of ships.

In this paper, electromagnetic interferences (EMI) occurred in electric power and telephone lines due to radiation at a frequency of 525 kHz from an aeronautical radio navigation station are presented. The induced voltages measured on those lines caused malfunction or even damage to some electrical devices inside the station. To understand those EMI effects further, an FDTD software package, XFDTD, was applied to evaluate the induced voltages. It was found that the major reasons resulting in interferences were due to longitudinally induced voltages and ground potential rises. They were caused by the radiation from the antenna of the station and current flowing through the ground grids, respectively. In addition, mitigation of EMI was performed to correct those problems by applying separate grounding systems, shielding the telephone, and using underground cables instead of overhead lines near the station. Currently, the whole system, including electric power, navigation and telephone, inside the station operates normally. [ABSTRACT FROM AUTHOR]

The main cause of the absolute positioning error in the Loran-C system is in the occurrence of the propagation time delay error caused by the fact that the propagation speed of the pulse signal on the actual propagation path is different from that assumed in the formation of the Loran-C maritime chart. The propagation path characteristics not only cause the propagation time delay of each received pulse signal but also generates waveform distortion in the received pulse. Hence, it is possible to estimate the propagation delay time by means of this waveform distortion. At present, a measure of the distortion of the pulse waveform distortion of the Loran-C is envelope to cycle difference (ECD). In this paper, as a new measure for the pulse-wave distortion to estimate the propagation time delay, CHACLE, or change of half-cycle length, is proposed. A method for correction of the absolute positioning error is provided based on the estimation of the propagation time delay from the measures of the waveform distortion (CHACLE end ECD) by means of the simplified propagation path for an easy analysis and of the general propagation path. It is demonstrated that CHACLE is superior to ECD in terms of the effect of correction. Further, to confirm the validity of the correction method proposed in this paper, the present method is applied to a propagation path model resembling the mixed propagation path used in the United States to estimate the pulse time delay. It is confirmed that the absolute positioning error can be reduced to less than about 20 percent. [ABSTRACT FROM AUTHOR]

The article discusses the origins of the Meteorological Office Radio Station (MORS) in South Farnborough, Hampshire, England. It notes that the meteorological office's origins are inextricably associated with the development of military aeronautics. It says that the office was established by the Army Council to provide meteorological support for the Balloon School. A research grant of £250 provided by the Advisory Committee for Aeronautics (ACA) to the MORS in 1910 is mentioned.