Link dependent origin-destination matrix estimation : nonsmooth convex optimisation with Bluetooth-inferred trajectories

This thesis tackles the traditional transport engineering problem of urban traffic demand estimation by using Bluetooth data and advanced signal processing algorithms. It proposes a method to recover vehicles trajectories from Bluetooth detectors and combining vehicle trajectories with traditional traffic datasets, traffic is estimated at a city level using signal processing algorithms. Involving new technologies in traffic demand estimation gave an opportunity to rethink traditional approaches and to come up with new method to jointly estimate origin-destinations flows and route flows. The whole methodology has been applied and evaluated with real Brisbane traffic data

Rosetta spacecraft influence on the mutual impedance probe frequency response in the long Debye length mode

International audienceDuring the Rosetta flyby of comet 46P/Wirtanen from 2011, plasma observations will be obtained from a number of instruments, the mutual impedance probe (MIP) is one of them. The mutual impedance technique is based on the measurements, as a function of the frequency the local plasma Debye length. The electron number density; is deduced from the electron plasma frequency at which the transfer function reaches its maximum, and the Debye length, lambda (D), is deduced from the positions of the minima above the plasma frequency. The long Debye length (LBL) mode, which operates in the 7-168 kHz range, is a secondary mode of MIP that has been designed to probe cometary plasmas when lambda (D) is longer than 70 cm. In that case, the Rosetta spacecraft presence cannot be neglected due to its conductive structures, the dimensions of which are of order of the emitter-receiver distance. A numerical simulation of the LDL mode is then necessary. The discrete surface charge distribution (DSCD) method, which is well adapted to the electric antenna problems in a kinetic plasma, would be suitable for the Rosetta flyby measurements. Here, all the conductive surfaces (spacecraft, solar panels and antennae) are compared with an alternating charge distribution that contributes to the LDL mode transfer function. The preliminary results show that in the early parts of the Rosetta mission, the cometary plasma can reasonably be considered to be Maxwellian, homogeneous? isotropic, collisionless and unmagnetized in the range of do from 0.7 to 2.5 m. The numerical results al e compared with those obtained by ignoring the spacecraft influence. It appears that the resonance peak at the plasma frequency is sharpest and strongest when the spacecraft influence is considered. Moreover, the antiresonance frequencies which occur on both sides of the plasma frequency depend on the Debye length of the surrounding plasma. Hence, the LDL mode should be able to measure the electron temperature in the range from about 10(4)-2 x 10(5) K. Plasmas with electron number densities lying between 22 and 180 cm(-3) should also be probed. This will allow the LDL mode to distinguish the boundary between the Wirtanen's cometary plasma and the Solar Wind in the prime investigations of the Rosetta mission, and this will complete the measurements made by the principal MIP mode in the non-magnetic cavity of the comet

RPC: The rosetta plasma consortium

International audienceThe Rosetta Plasma Consortium (RPC) will make in-situ measurements of the plasma enviromnent of comet 67P/Churyumov-Gerasimenko. The consortium will provide the complementary data sets necessary for an understanding of the plasma processes in the inner coma, and the structure and evolution of the coma with the increasing cometary activity. Five sensors have been selected to achieve this: the Ion and Electron Sensor (IES), the Ion Composition Analyser (ICA), the Langmuir Probe (LAP), the Mutual Impedance Probe (MIP) and the Magnetometer (MAG). The sensors interface to the spacecraft through the Plasma Interface Unit (PIU). The consortium approach allows for scientific, technical and operational coordination, and makes Optimum use of the available mass and power resources