Performances of a GNSS receiver for space-based applications

Space Vehicle (SV) life span depends on its station keeping capability. Station keeping is the ability of the vehicle to maintain position and orientation. Due to external perturbations, the trajectory of the SV derives from the ideal orbit. Actual positioning systems for satellites are mainly based on ground equipment, which means heavy infrastructures. Autonomous positioning and navigation systems using Global Navigation Satellite Systems (GNSS) can then represent a great reduction in platform design and operating costs. Studies have been carried out and the first operational systems, based on GPS receivers, become available. But better availability of service could be obtained considering a receiver able to process GPS and Galileo signals. Indeed Galileo system will be compatible with the current and the modernized GPS system in terms of signals representation and navigation data. The greater availability obtained with such a receiver would allow significant increase of the number of point solutions and performance enhancement. For a mid-term perspective Thales Alenia Space finances a PhD to develop the concept of a reconfigurable receiver able to deal with both the GPS system and the future Galileo system. In this context, the aim of this paper is to assess the performances of a receiver designed for Geosynchronous Earth Orbit (GEO) applications. It is shown that high improvements are obtained with a receiver designed to track both GPS and Galileo satellites. The performance assessments have been used to define the specifications of the future satellite GNSS receiver

A flexible implementation of a Global Navigation Satellite System receiver for on-board satellite navigation

In this paper, we present the implementation of the acquisition algorithm of a versatile Global Navigation Satellite System (GNSS) receiver for satellite applications. For versatility purpose, the choice of the receiver algorithms has been motivated by 1) their capability to fulfill the application requirements with a moderate complexity, 2) their capability of being factorized in a small set of elementary modules that can be configured and combined in various ways in order to process both GPS and Galileo current and future signals. These algorithms have been specified using SystemC, a modeling language that can be common to hardware and software flow. The use of a virtual platform for simulation allows us to identify bottleneck of the architecture and to propose algorithm modification to solve them

L'évolution des avantages comparatifs révélés du secteur manufacturier au Canada et au Mexique, 1980-2002

Numéro de référence interne originel : a1.1 g 111

Accurate Events Synchronization in a System-on-Chip Navigation Receiver

International audienceA System-On-Chip design and synchronization details of a navigation receiver are presented. The architecture of the GNSS receiver is easily modifiable and offers the capability of accurate time management, thanks to the use of a co-design approach. The purpose of such a platform is to allow real time validation of research algorithms. A secondary application is education, as this platform can be used to study signal demodulation and navigation. The receiver is fully functional, but further developments are still undergoing. Results demonstrate accuracy, flexibility and ease of use of the system

On the nonparametric inference of coefficients of self-exciting jump-diffusion

In this paper, we consider a one-dimensional diffusion process with jumps driven by a Hawkes process. We are interested in the estimations of the volatility function and of the jump function from discrete high-frequency observations in a long time horizon which remained an open question until now. First, we propose to estimate the volatility coefficient. For that, we introduce a truncation function in our estimation procedure that allows us to take into account the jumps of the process and estimate the volatility function on a linear subspace of L2(A) where A is a compact interval of R. We obtain a bound for the empirical risk of the volatility estimator, ensuring its consistency, and then we study an adaptive estimator w.r.t. the regularity. Then, we define an estimator of a sum between the volatility and the jump coefficient modified with the conditional expectation of the intensity of the jumps. We also establish a bound for the empirical risk for the non-adaptive estimators of this sum, the convergence rate up to the regularity of the true function, and an oracle inequality for the final adaptive estimator.Finally, we give a methodology to recover the jump function in some applications. We conduct a simulation study to measure our estimators' accuracy in practice and discuss the possibility of recovering the jump function from our estimation procedure

Real Time Estimation of rigid body orientation based on inertial sensors measurements

International audienceThis paper presents a programmable DSP board developed for real-time estimation of rigid body orientation. This work takes place in a research project carried out by students. The project consists of unmanned aerial vehicle’s (UAV) attitude estimation. This estimation is processed by an Inertial Reference System (IRS) including the TMS320F2812 processor, low cost integrated Micro Electro Mechanical Systems (iMEMS) such as accelerometers and gyroscopes, temperature sensors, and magnetometers. Gyroscopes provide angular velocities that can be integrated to yield orientation. Accelerometers and magnetometers, pointing to gravity direction and north direction enables drift compensation. So the system performs a drift-free attitude estimation using quaternions for rotations representation. One benefit of this system is that it enables high integration by exploiting the processor’s capacities for sensors interfacing. Moreover it takes advantage of the high performance processor to achieve a real time estimation of the body’s orientation. For that digital processing includes signals filtering, measurements compensation and a lot of trigonometric functions for Euler angles computing. The system performances can be measured using a PC for results visualisation. The system has been designed to integrate in the future GPS component and pressure sensor. These components will allow more accurate attitude estimation and positioning

Demo: Localisation in a faulty digital GPS receiver

The increase in integration density and the requirement of low power supplies to reduce energy consumption can make circuits more and more sensitive to hardware errors. The loss of robustness increases with process/voltage and temperature (PVT) variations. This demo presents a platform used first to implement a noiseless GPS receiver algorithm. Redundant mechanisms can be added, then, to the design to make the GPS receiver more resilient against upset errors due low supply voltage. The platform can be used, so, to evaluate the performance and the complexity of the proposed mechanisms

Accurate Events Synchronization in a System-on-Chip Navigation Receiver

A System-On-Chip design and synchronization details of a navigation receiver are presented. The architecture of the GNSS receiver is easily modifiable and offers the capability of accurate time management, thanks to the use of a co-design approach. The purpose of such a platform is to allow real time validation of research algorithms. A secondary application is education, as this platform can be used to study signal demodulation and navigation. The receiver is fully functional, but further developments are still undergoing. Results demonstrate accuracy, flexibility and ease of use of the system

Single-Frequency High-Power Continuous-Wave Oscillation at 1003 nm of an Optically Pumped Semiconductor Laser

This work reports single-frequency laser oscillation at 1003.4 nm of an optically pumped external cavity semiconductor laser. By using a gain structure bonded onto a high conductivity substrate, we demonstrate both theoretically and experimentally the strong reduction of the thermal resistance of the active semiconductor medium, resulting in a high power laser emission. The spectro-temporal dynamics of the laser is also explained. Furthermore, an intracavity frequency-doubling crystal was used to obtain a stable single-mode generation of blue (501.5 nm) with an output power around 60 mW.Comment: 11 page