A Large Along-Track Baseline Approach for Ground Moving Target Indication Using TanDEM-X

In the paper a new method for ground moving target indication (GMTI) using two satellites (i.e. the TerraSAR-X and the TanDEM-X satellite) together is presented. The along-track baseline between the satellites is chosen to be in the order of several kilometres, so that each satellite observes the same moving vehicles at different times in the order of one to several seconds. The proposed method allows the estimation of the ground velocity of the moving targets as well as the estimation of the broadside positions without the need of complex bistatic processing techniques

Digital Beamforming and Traffic Monitoring Using the new FSAR System of DLR

In November 2006 the first X-band test flight of DLR’s new FSAR system has been performed successfully and in February 2007 the first flight campaign has been conducted for acquiring experimental multi-channel data of controlled ground moving targets. In the paper the performed experiments and the used setup of the FSAR X-band section are described and preliminary results in the field of ground moving target indication and digital beamforming are presented

Impact of Road Vehicle Accelerations on SAR-GMTI Motion Parameter Estimation

In recent years many powerful techniques and algorithms have been developed to detect moving targets and estimate their motion parameters from single- or multi-channel SAR data. In case of single- and two-channel systems, most of the developed algorithms rely on analysis of the Doppler history. Nowadays it is known, that even small unconsidered across-track accelerations can bias the along-track velocity estimation. Since we want to monitor real and more complex traffic scenarios with a future traffic monitoring system like TRAMRAD, we must know which target accelerations we have to handle in reality. For this reason a common passenger car was equipped with an inertial measurement system and differential GPS to measure accelerations in all three dimensions during rush-hour traffic. In this paper the results of the acceleration measurements are presented and discussed. The standard deviations of the measured accelerations are in the order of 0.5 m/s2 for accelerations in driving direction and 0.6 m/s2 for radial accelerations. A theoretical analysis (which is verified by detailed simulations) of the Doppler slope shows also that at such high across-track accelerations a reliable estimation of the along-track velocity by means of a Doppler slope analysis without further information is unemployable in practice. Also oscillations of the car body along the vertical axis are investigated in this paper. From the field of vehicle dynamics it is known that the eigen frequencies of the car body are in the range from 0.7 to 2.0 Hz. Deflections in the order of one wavelength (X-band) or higher are possible at such frequencies. The simulation results for spaceborne SAR systems with integration times in the order of one second show that the shape and azimuth shift of the impulse response depend beside the oscillation frequency and the deflection also on the initial phase of the oscillation. However, at practical applications the main part of the energy could also be reflected by double bounce from the road surface. Thus, further investigations in the topic of vehicle oscillations by using real radar data are necessary. Finally, some basic ideas are presented which enable a reliable separation between along-track velocity and across-track acceleration. For example, the easiest way to separate both just mentioned motion parameters is the use of a road database, from which the information about the motion direction of the assigned vehicle can be extracted. Hence, the accuracy of along-track velocity estimation is mainly given by the accuracy of the estimated across-track velocity and the angle of the road section in relation to the flight path of the SAR platform

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements