High-frequency global navigation satellite system's receivers for airborne gravimetry

The development of global navigation satellite systems (GNSS) provides a solution of many applied problems with increasingly higher quality and accuracy nowadays. Researches that are carried out by the Bavarian Academy of Sciences and Humanities in Munich (BAW) in the field of airborne gravimetry are based on sophisticated data processing from high frequency GNSS receiver for kinematic aircraft positioning. Applied algorithms for inertial acceleration determination are based on the high sampling rate (50Hz) and on reducing of such factors as ionosphere scintillation and multipath at aircraft /antenna near field effects. The quality of the GNSS derived kinematic height are studied also by intercomparison with lift height variations collected by a precise high sampling rate vertical scale [1]. This work is aimed at the ways of more accurate determination of mini-aircraft altitude by means of high frequency GNSS receivers, in particular by considering their dynamic behaviour

Expression, purification, and crystallization of bacteriorhodopsin and its derivatives

Energy production in a living cells is among the most important questions in biology and for the modern technology. Bacteriorhodopsin (bR) being a simplest tool to produce electric potential across membrane have received a lot of attention. It became one of the model membrane proteins, also because of its relative abundance in nature and relative ease of purification from natural source, H. salinarum. Unique properties of bR photocycle make it useful and promising in a wide variety of technical applications, thus giving rise to growing need of this protein. Despite the availability of the atomic structures there are still controversies in mechanism of proton pumping by bR. Homologous production of bR and its mutants in halobacteria is laborious, time-, and resource-consuming, therefore facile and robust E. coli expression system would be of wide interest. Recently several structures of GPCRs were obtained using GPCR-lysozyme fusion protein where lysozyme served as a crystallization tag. We suppose that bR would be a good model for investigation of versatility of lysozyme as crystallization tags. As in meso grown crystals of bR are prone to twinning crystallization of bR-lysozyme fusion protein could provide twinning-free crystals allowing to clarify the details of bR photocycle. In this work, it was suggested that the low yield of bR expression in E. coli can be attributed to the poor insertion of the protein into membrane. We have introduced protein complementary approach that may allow to localize the problem in membrane protein expression using finite number of steps. It is based on constructing of chimeric proteins between a protein of interest and complementary homologous protein expressed with high yield. Applying this approach we showed that the substitution of first ten amino acids of bR for the corresponding eight amino acids from SRII increase the expression yield of bR more than 50-fold. The reason for high yield of the chimera could be the positively charged Arg7 on the N-terminus of bR that deviates from “positive inside” rule and absent in the chimera. We expressed bR mutants R7Q and R7E where this positive charge was substituted for neutral and negative charges, respectively. Although the yields of the mutants were higher than of wild type gene, they were still considerably lower than yield of chimera. Thus, the positive charge on the N-terminus of bR is not the reason of its poor expression in E. coli. A putative stem structure 5'-end of bR mRNA was proposed to be another reason of low bR expression in E. coli. The expression yield of optimized wild type bR gene was on the same level as yield of the chimera. Therefore, the low yield of bacteriorhodopsin native gene in E. coli was attributed to the unfavorable mRNA structure of native gene close to the ribosome binding site. When purified under non-denaturing conditions, the protein have retained its functionality. The yield of functional homogenious protein was 2.4±1.3 mg per liter of culture what is sufficient for a large-scale crystallization and industrial use. Using this approach we produced as well functional V49A, D85N, and D96N mutants of bR in short time with yields of 0.3, 3.8, and 8.8 mg per liter of culture, respectively. We suppose that increased yield of D85N and D96N mutants can be explained by better incorporation of positively charged C-helix of bR into E. coli membrane. The second goal, crystallization of the bR-lysozyme fusion protein, demands a high yield expression system and effective crystallization approaches. Here, bR can serve as a reference. High resolution structures show that bR trimers are surrounded by the belt of native lipid. Despite multiple protocols of E. coli expression, 3D crystallization of this protein was not reported. Since expressed in E. coli bR-lysozyme fusion protein would not have H. salinarum lipids bound and purification of this protein is based on the application of DDM instead of usual OG, careful investigation of the influence of lipid/detergent environment on in meso crystallization is important. To study the influence of detergent on the in meso crystallization we set large-scale crystallization trials with homologously expressed bR in mixtures of detergents. The crystals of different size (up to 300 μm) were obtained. Three crystals grown in mixtures of detergents radiation gave at synchrotron a diffraction up to 1.45 Å. The full datasets were collected and three structures of bR were solved. We have not observed detergent molecules on the electron densities corresponding to the structures. These experiments showed that detergent molecules do not participate in the formation of the crystal lattice of bR. Moreover, there is no need to exchange the detergent from DDM used for purification to OG that is generally used for in meso crystallization of homologously expressed bR. Then, using the protein expressed E. coli the crystals of wild type bR and D85N and D96N bR mutants were grown. Crystals were tested under synchrotron radiation and gave a diffraction up to 2.5Å resolution. The first 3D crystals of bR expressed in E. coli demonstrate that expression of bR and its mutants in E. coli is suitable for scientific and industrial applications. In addition, the successful crystallization of protein isolated from E. coli demonstrated that H. salinarum lipids are not strictly required for grow of well ordered bR crystals. Using the optimized bR gene we have expressed bR-lysozyme fusion proteins in E. coli with yield up to 0.9 mg of functional protein per liter of culture. This protein was purified under non-denaturing conditions to homogeneity and in meso crystallization trials are ongoing

Исследования и испытания алгоритмов автоматической пилотажно-навигационной системы малогабаритного беспилотного летательного аппарата = Research and testing of automatic navigation management system’s algorithms for small unmanned aerial vehicle

В статье представлено развитие принципа построения автоматической пилотажно-навигационной системы (АПНС) для беспилотного летательного аппарата (БЛА). Принцип заключается в синтезе комплексных систем управления БПЛА не только на основе использования алгоритмов БИНС, но и алгоритмов, объединяющих в себе решение задач формирования и отработки сформированной траектории резервированной системой управления и навигации.\ud Приведены результаты аналитического исследования и данные летных экспериментов разработанных алгоритмов АПНС БЛА, обеспечивающих дополнительное резервирование алгоритмов навигации и наделяющих БЛА новым функциональной способностью по выходу в заданную точку пространства с заданной скоростью в заданный момент времени с учетом атмосферных ветровых возмущений. Предложена и испытана методика идентификации параметров воздушной атмосферы: направления и скорости W ветра. Данные летных испытаний полученного решения задачи терминальной навигации демонстрируют устойчивую работу синтезированных алгоритмов управления в различных метеоусловиях.\ud \ud The article presents a progress in principle of development of automatic navigation management system (ANMS) for small unmanned aerial vehicle (UAV). The principle defines a development of integrated control systems for UAV based on tight coupling of strap down inertial navigation system algorithms and algorithms of redundant flight management system to form and control flight trajectory. The results of the research and flight testing of the developed ANMS UAV algorithms are presented. The system demonstrates advanced functional redundancy of UAV guidance. The system enables new UAV capability to perform autonomous multidimensional navigation along waypoints with controlled speed and time of arrival taking into account wind. The paper describes the technique for real-time identification of atmosphere parameters such as wind direction and wind speed. The flight test results demonstrate robustness of the algorithms in diverse meteorological conditions

A vision-based sense-and-avoid system tested on a ScanEagle UAV

This paper presents a study of near collision course engagements between a Cessna 172R aircraft and a ScanEagle UAV carrying a custom built vision-based sense-and-avoid system. Vision-based systems are an attractive solution for the sense-and-avoid problem because of size, weight and power considerations. We present post flight test analysis that shows our detection system successfully detecting an approaching Cessna aircraft in all 15 flight test encounters at ranges greater than 1500 m, with no false alarms events. Moreover, this paper characterises the image inter-frame stabilisation required to achieve acceptable detection performance, and compares a range of stabilisation techniques for achieving this type of stabilisation precision. Our analysis illustrates that the image inter-frame stabilisation requirements are demanding, suggesting that images must be stabilised in real-time at 9Hz to within 2 pixels between consecutive frames. We present performance comparisons between stabilisation using GPS/INS, IMU-only and image-based techniques

UAVs, Hyperspectral Remote Sensing, and Machine Learning Revolutionizing Reef Monitoring

Recent advances in unmanned aerial system (UAS) sensed imagery, sensor quality/size, and geospatial image processing can enable UASs to rapidly and continually monitor coral reefs, to determine the type of coral and signs of coral bleaching. This paper describes an unmanned aerial vehicle (UAV) remote sensing methodology to increase the efficiency and accuracy of existing surveillance practices. The methodology uses a UAV integrated with advanced digital hyperspectral, ultra HD colour (RGB) sensors, and machine learning algorithms. This paper describes the combination of airborne RGB and hyperspectral imagery with in-water survey data of several types in-water survey of coral under diverse levels of bleaching. The paper also describes the technology used, the sensors, the UAS, the flight operations, the processing workflow of the datasets, the methods for combining multiple airborne and in-water datasets, and finally presents relevant results of material classification. The development of the methodology for the collection and analysis of airborne hyperspectral and RGB imagery would provide coral reef researchers, other scientists, and UAV practitioners with reliable data collection protocols and faster processing techniques to achieve remote sensing objectives

Radar-Aided Optical Navigation for Long and Large-Scale Flights over Unknown and Non-Flat Terrain

For flight automation tolerable to satellite navigation dropouts, this paper presents a simultaneous localization and mapping method based on radar altimeter measurements and monocular camera images. The novelty within mapping is the combination of radar distance and image triangulation. This approach verifies whether the radar measurement fits to a specific horizontal plane in the map, yielding the sub-set of image features that do most probably correspond with the radar measurement. With this map match of the radar altitude, ambiguities in the radar measurement can be resolved. Since unusable radar measurements are suppressed, this method is suitable for positioning in non-flat terrain, e.g. in mountain areas. For matched data, the method estimates a scale correction factor for the image projection rays in order to remove scale ambiguities of the monocular navigation. Together with mapping, vehicle localization is done which is essentially camera resectioning. Localization can be parameterized with the required number of degrees of freedom depending on the availability of additional position sensors. The incremental positioning is tested in kilometer-scale outdoor flights of a 30~kg unmanned airplane as well as in flights with a Cessna 172R equipped with camera and radar sensors. The tests show the benefits of the proposed method in flat and hilly terrain, and demonstrate reduction of accumulation errors down to 2-6% over the distance flown. Some constraints of the method for the altitude range are existent, however it is highlighted that this method will generally work on typical flight profiles