Recent years have seen ambitious robotic exploration missions to other planets and a renewed interest in sending humans beyond low Earth orbit. These activities give rise to a need for autonomous spacecraft operation. Of particular interest here is the ability of a spacecraft to navigate independent of contact with Earth-based resources. Optical navigation techniques are proposed as a solution to the problem of navigating in a planetary system without requiring navigation information from Earth. A detailed discussion of optical sensor hardware and error sources leads to new high fidelity math models for optical sensor performance that may be used in navigation simulations. Algorithms are developed that allow optical data to be used for the estimation of spacecraft position, velocity, and attitude. Sequential measurements are processed using traditional filtering techniques. Additionally, for the case of attitude estimation, a new attitude filter called Sequential Optimal Attitude Routine (SOAR) is presented. The models and techniques developed in this dissertation are demonstrated in two case studies: (1) navigation of a spacecraft performing a planetary fly-by using real images from the June 2007 MESSENGER fly-by of Venus and (2) navigation of a spacecraft in cislunar space on a return trajectory from the Moon. / text

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International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / GPS is required in today's vehicle tracking and navigation applications. The Navigation Satellite Timing and Ranging (NAVSTAR GPS) is an all-weather. Radio based, satellite navigation system that enables users to accurately determine 3-dimensional position, velocity and time. So it is an intelligent sensor intended to be used as a component in a system for public service.

Zielsetzung: In dieser Machbarkeitsstudie evaluierten wir den aktuellen Standard der linksventrikulären Endomyokardbiopsie in einem Modellversuch. Wir entwickelten und überprüften mögliche Verbesserungen hinsichtlich ihrer Sicherheit und Punktionsgenauigkeit, indem wir eine steuerbare Schleuse und ein 3D Mapping-System zum Einsatz brachten. Hintergrund: Die Endomyokardbiopsie gilt als Goldstandard zur Diagnostik von Myokarditiden und Kardiomyopathien, da sie histochemische, histologische und molekularbiologische Analysen ermöglicht, die für eine korrekte Diagnose und Therapie wichtig sind. Die Methodik hat eine verhältnismäßig geringe Sensitivität und einen niedrigen negativen prädiktiven Wert, da das Myokard derzeit unter Röntgendurchleuchtung biopsiert wird, ohne eine genaue Orientierung im dreidimensionalen Raum oder eine Kenntnis der z.T. diskontinuierlich betroffenen Myokardareale zu haben (sogenannter „sampling error“). Methoden: Wir testeten die Steuerbarkeit und die Punktionsgenauigkeit der Endomyokardbiopsie im Modellversuch, indem wiederholt Biopsien von acht verschiedenen linksventrikulären Herzregionen genommen werden. In einer dreiarmigen Studie optimierten wir zum einen die invasiv-apparative Ausrüstung und zum anderen die verfügbare Bildgebungsmodalität. Der Kontrollversuch I repräsentiert eine Analyse des aktuellen Standards, da hier Biopsien mit konventionellen Führungskathetern unter Röntgendurchleuchtung erfolgen. Der Kontrollversuch II untersucht, ob mittels einer steuerbaren Schleuse unter konventioneller Bildgebung eine Verbesserung erzielt werden kann. Im dritten Teil der Studie wurde die Röntgendurchleuchtung durch ein 3D elektroanatomisches Mapping-System ersetzt. Hiermit kann erstmalig die Machbarkeit der Navigation einer steuerbaren Schleuse in einem 3D Mapping-System geprüft werden. Ergebnisse: Jeder der eingesetzten konventionellen Führungskatheter ist für die Biopsie einer bestimmten Herzregionen geeignet, jedoch hat die konventionelle Methodik bei wiederholten Messungen allgemein eine niedrige Präzision (JR 4.0 Führungskatheter: 17,4 ± 4 mm, AL 1.0 Führungskatheter: 18,7 ± 5,7 mm, EBU 3.5 Führungskatheter: 18,3 ± 8,2 mm). Durch den Einsatz der neu entwickelten steuerbaren Schleuse konnten einige der gewünschten Stellen zwar korrekter biopsiert werden, aber eine allgemein sichere Ansteuerung aller Positionen war damit noch nicht möglich (9,5 ± 5,8 mm). Die bildliche Darstellung der steuerbaren Schleuse im 3D Mapping-System gelang sehr gut, die Biopsiezange konnte mit der Schleuse leicht und mit einer höheren Präzision an fast alle gewünschten Herzregionen navigiert werden (3,6 ± 2 mm). Fazit: Die hier vorgelegte Machbarkeitsstudie zeigt, dass der Einsatz einer neuentwickelten steuerbaren Schleuse in Kombination mit einem 3D Mapping-System möglich und erfolgversprechend ist. Die Ergebnisse der Biopsien im elektroanatomischen Mapping-Versuch wiesen im Mittel eine deutlich geringere Abweichung beim wiederholten Ansteuern der jeweilig gewünschten Zielregion auf. Mittels der neuentwickelten Technik kann somit die Endomyokardbiopsie im Vergleich zum Standardverfahren präziser und mit einer potentiell höheren Patientensicherheit durchgeführt werden. / Objectives: In this proof of principle study we evaluated the current standard of leftventricular endomyocardial biopsy in an in-vitro test and developed and assessed improvements concerning safety and accurateness by making use of a steerable sheath and a 3D mapping system. Background: Endomyocardial biopsy represents the gold standard for diagnosing myocarditis and certain cardiomyopathies as it allows histology, immunhistochemistry and molecular biology studies which add to diagnosis and therapy. Nevertheless, the sensitivity and negative predictive value are comparatively low, as the biopsy is currently performed under fluorescence imaging without three-dimensional orientation and without exact knowledge of the partly discontinuously affected myocardium (so called sampling error). Methods: We tested the controllability and accuracy of endomyocardial biopsy in simulation tests by taking repetitive biopsies of 8 different leftventricular cardiac regions. In a three-arm study we first optimized the invasive technical equipment and second the available imaging technique. Control experiment one illustrates an analysis of the current standard as biopsies were taken with conventional diagnostic catheters under fluorescence imaging. In control experiment two the ability of improvement by the use of a steerable sheath under conventional imaging was checked. In part three of the study the fluorescence imaging was replaced by a three-dimensional electroanatomical mapping system. This simulation test represents a proof of principle for the first time navigation of a steerable sheath in a 3D mapping system. Results: Each tested standard guiding catheter was suited for biopsy of a particular part of the myocardium, although the conventional method in general proved to have a low accuracy in repetitive measurements (e.g. JR 4.0 guiding catheter: 17.4 ± 4 mm, AL 1.0 guiding catheter: 18.7 ± 5.7 mm, EBU 3.5 guiding catheter: 18.3 ± 8.2 mm). By the use of the newly developed steerable sheath in some requested regions the biopsy could be taken with higher precision, but a general save approach to all regions was still not possible (9.5 ± 5.8 mm). The electroanatomical mapping experiment revealed an excellent visualization of the steerable sheath in the 3D mapping system, allowing the biopsy forceps to be easily navigated by the sheath to almost all of the requested areas with higher precision (3.6 ± 2 mm). Conclusions: The use of a steerable sheath in combination with a 3D mapping system is possible and promising. The biopsy results of the electroanatomical mapping experiments showed on average clearly less deviation in repetitive approaches to the respective target areas. With the newly developed technique endomyocardial biopsy can be realized with higher accuracy and potentially more patient safety compared to the standard procedure.

This thesis describes the theoretical and practical implementation of a long-range high-resolution millimetre wave imaging radar system to aid with the navigation and guidance of both airborne and ground-based autonomous vehicles. To achieve true autonomy, a vehicle must be able to sense its environment, comprehensively, over a broad range of scales. Objects in the immediate vicinity of the vehicle must be classified at high resolution to ensure that the vehicle can traverse the terrain. At slightly longer ranges, individual features such as trees and low branches must be resolved to allow for short-range path planning. At long range, general terrain characteristics must be known so that the vehicle can plan around difficult or impassable obstructions. Finally, at the largest scale, the vehicle must be aware of the direction to its objective. In the past, short-range sensors based on radar and laser technology have been capable of producing high-resolution maps in the immediate vicinity of the vehicle extending out to a few hundred metres at most. For path planning, and navigation applications where a vehicle must traverse many kilometres of unstructured terrain, a sensor capable of imaging out to at least 3km is required to permit mid and long-range motion planning. This thesis addresses this need by describing the development a high-resolution interrupted frequency modulated continuous wave (FMICW) radar operating at 94GHz. The contributions of this thesis include a comprehensive analysis of both FMCW and FMICW processes leading to an effective implementation of a radar prototype which is capable of producing high-resolution reflectivity images of the ground at low grazing angles. A number of techniques are described that use these images and some a priori knowledge of the area, for both feature and image based navigation. It is shown that sub-pixel registration accuracies can be achieved to achieve navigation accuracies from a single image that are superior to those available from GPS. For a ground vehicle to traverse unknown terrain effectively, it must select an appropriate path from as long a range as possible. This thesis describes a technique to use the reflectivity maps generated by the radar to plan a path up to 3km long over rough terrain. It makes the assumption that any change in the reflectivity characteristics of the terrain being traversed should be avoided if possible, and so, uses a modified form of the gradient-descent algorithm to plan a path to achieve this. The millimetre wave radar described here will improve the performance of autonomous vehicles by extending the range of their high-resolution sensing capability by an order of magnitude to 3km. This will in turn enable significantly enhanced capability and wider future application for these systems.