Meiko Steen

Testbed for dual-constellation GBAS concepts

Satellite based Navigation Systems (Global Navigation Satellite System GNSS) will become a major element in the navigation infrastructure of the future. In addition to classical en-route and terminal navigation, where GNSS is increasingly used, approach and landing procedures are being developed and implemented based on GNSS. To meet the requirements of integrity, accuracy, continuity and availability for precision approach and landing operations, augmentation systems are needed. Currently there are two augmentation systems for these periods of flight available: Ground Based Augmentation Systems (GBAS) and Space Based Augmentation Systems (SBAS).

Analysis and evaluation of MEMS INS/GNSS hybridization for commercial aircraft and business jets

The rapid evolution of inertial Micro-Electro-Mechanical System (MEMS) sensors offers the opportunity to replace expensive conventional Air Data Inertial Reference Units (ADIRU) in future aircraft navigation systems. Particularly with the advent of modernized GNSS and multi-constellation systems, the expected performances of future GNSS-aided Attitude and Heading Reference Systems (G-AHRS) are supposed to satisfy the current requirements. Since MEMS exhibit limitations in their accuracy nowadays, detailed investigations are needed to evaluate the possibility of using them within G-AHRS and also for navigation in the short, mid or long term. This papers deals with the usability of MEMS sensors with current and expected future performance. This evaluation was done based on real flight test data and simulation of future MEMS sensors. While current MEMS cannot completely fulfill all needed requirements, future sensors are expected to satisfy them.

New Concept for Wake-Vortex Hazard Mitigation Using Onboard Measurement Equipment

Wake-vortex hazards are a huge threat in aviation. These hazards are well accepted in the vicinity of airports (both departure and arrival). But also a number of en route incidents have happened in the past. Current wake-vortex mitigation strategies are based on static distances (in space and/or time). In future air traffic management concepts of Single European Sky Air Traffic Management Research and NextGen, these static distances will be replaced by dynamic separation strategies. Furthermore, concepts for self-separation of aircraft are described. This paper will discuss the work at Technische Universitat Braunschweig, where a new concept for wake-vortex hazard mitigation has been developed. The basic idea of the new concept is that only a criticality parameter will be transmitted between aircraft to ensure a safe separation even within new self-separation concepts. The criticality parameter will give an indication about the severity (and therefore criticality to the following aircraft) of the vortices...

Towards wake vortex safety and capacity increase: the integrated fusion approach and its demands on prediction models and detection sensors

Wake vortices and the prevention of wake vortex encounters are both an issue of safety and capacity in today’s air transportation system. Current wake vortex separations are safe but also very conservative and thus have an adverse effect on capacity of airports. This article deals with the concept of fused wake vortex prediction and detection with the objective to deliver wake vortex strength and position with a high level of accuracy and reliability. The collaboration approach aims at fusion of models and sensors available for forecast and detection of hazardous wake turbulence in order to improve the overall system performance using the complementary capabilities of the single components. Different methods of coupling models with measurements are introduced and resulting the aspect of requirements for the prediction model and measurement sensor is presented. The implementation of an error-state system is presented and compared to sole prediction and sole sensor results. The results indicate that the fusion approach delivers benefits like reduced uncertainty of prediction and increased availability of detection and thus has the ability to increase airport and air space capacity while maintaining or even improving current wake vortex safety.

The far-infrared space interferometer study IRASSI: motivation, principle design, and technical aspects

The far-infrared (FIR) regime is one of the few wavelength ranges where no astronomical data with sub-arcsecond spatial resolution exist yet. Also medium-term satellite projects like SPICA, Millimetron or OST will not resolve this malady. For many research areas, however, information at high spatial and spectral resolution in the FIR, taken from atomic fine-structure lines, from highly excited CO and especially from water lines would open the door for transformative science. These demands call for interferometric concepts. We present here first results of our feasibility study IRASSI (Infrared Astronomy Satellite Swarm Interferometry) for an FIR space interferometer. Extending on the principal concept of the previous study ESPRIT, it features heterodyne interferometry within a swarm of 5 satellite elements. The satellites can drift in and out within a range of several hundred meters, thereby achieving spatial resolutions of <0.1 arcsec over the whole wavelength range of 1–6 THz. Precise knowledge on the baselines will be ensured by metrology employing laser frequency combs, for which first ground-based tests have been designed by members of our study team. In this contribution, we first give a motivation how the science requirements translated into operational and design parameters for IRASSI. Our consortium has put much emphasis on the navigational aspects of such a free-flying swarm of satellites operating in relatively close vicinity. We hence present work on the formation geometry, the relative dynamics of the swarm, and aspects of our investigation towards attitude estimation. Furthermore, we discuss issues regarding the real-time capability of the autonomous relative positioning system, which is an important aspect for IRASSI where, due to the large raw data rates expected, the interferometric correlation has to be done onboard, quasi in real-time. We also address questions regarding the spacecraft architecture and how a first thermomechanical model is used to study the effect of thermal perturbations on the spacecraft. This will have implications for the necessary internal calibration of the local tie between the laser metrology and the phase centres of the science signals.

Adaptive Nonlinear Flight Control of STOL-Aircraft Based on Incremental Nonlinear Dynamic Inversion

In this paper an adaptive control system for a passenger aircraft with active high-lift system is presented. Failures in the high-lift system parts of such aircraft are critical and consequently need to be handled automatically. An adaptive controller is proposed which consists of incremental nonlinear dynamic inversion (INDI) with a reference model and linear controller. As the INDI is adaptive against uncertainties or system failures, no additional adaptive element like a neural network is needed. The implementation of the INDI requires a nonlinear system model which is permanently linearized during the runtime in order to obtain the current input matrix which here basically consists of the control surfaces effectiveness. It also requires feedback of the translational and rotational acceleration measurements which usually suffer from noise. In order to test the adaptivity of the INDI, a partial failure of the high-lift system during the landing approach is regarded. It shows that the INDI is capable of compensating the error by only using the conventional control surfaces.