ESA's planning and coordination of the OLYMPUS propagation experiment

An overview of the organization of the OLYMPUS propagation experimenters group (OPEX) is given. Preparations, participation, and experiments are described. Some examples for first statistical results are also reported. OLYMPUS, a 3-axis stabilized communications satellite was launched in 1989 for providing experimental telecommunications payloads and a propagation beacon payload at 12, 20, and 30 GHz to the European Space Agency. From previous experience (OTS), the Agency undertook to carry out extensive preparations with an eye on obtaining the statistical results needed within the limited available lifetime of the spacecraft. The OLYMPUS propagation experiment was conceived as part of ESA's space telecommunications applications program (ESA/IPC/(79)83) with the emphasis on exploring the possibilities and limitations of Ka-band satellite communications. The objectives of the OLYMPUS propagation campaign were: (1) characterization of the slant-path propagation conditions at 20/30 GHz in the various climatic regions of Europe; (2) improvement of the understanding of the link between atmospheric observable (rain rate, cloud thickness, etc.) to propagation impairments such as attenuation, depolarization, scintillation, etc.; and (3) arrive at improved propagation prediction methods

A review of OPEX activities and measurement results

A summary is given of the measurements carried out in the framework of OPEX (OLYMPUS Propagation Experimenters Group). In particular, the progress since mid-1990 is presented. In this period two OPEX meetings were held, OPEX 14 (Oct. 1990) and OPEX 15 (Apr. 1991). The First OPEX Workshop was held at ESTEC on 23-24 April 1991

The ISIS Project: Indications for Future Near-Earth Plasma Studies through Future Galileo Satellites

The Earth’s plasmasphere variability is a consequence of the Sun’s forcing, determining our planet’s space weather. Plasmaspheric dynamics could be entirely caught only by studying together global and local proxies of the state of this extended system. The ISIS project (Inter-Satellite & In Situ plasmaspheric monitoring and modelling) aimed to design a system for the continuous monitoring of the Earth’s plasmasphere based on the future Galileo satellites. The efforts and expertise of ISC-CNR (Institute for Complex Systems of the National Research Council of Italy), INGV (Istituto Nazionale di Geofisica e Vulcanologia) and TAS-I (Thales Alenia Space - Italy) were put together in this work of assessment. ISIS Team proposed new experimental facilities of the Galileo satellites, designed to realize inter-satellite and in situ measurements to monitor global and local quantities; in particular, a scalable system of Langmuir probes was suggested, while the TEC along all possible inter-satellite ray paths throughout the plasmasphere could be monitored via phase- and group-delay analysis of inter-satellite radio signals

The ISIS Project: Indications for Future Near-Earth Plasma Studies through Future Galileo Satellites

The Earth’s plasmasphere variability is a consequence of the Sun’s forcing, determining our planet’s space weather. Plasmaspheric dynamics could be entirely caught only by studying together global and local proxies of the state of this extended system. The ISIS project (Inter-Satellite & In Situ plasmaspheric monitoring and modelling) aimed to design a system for the continuous monitoring of the Earth’s plasmasphere based on the future Galileo satellites. The efforts and expertise of ISC-CNR (Institute for Complex Systems of the National Research Council of Italy), INGV (Istituto Nazionale di Geofisica e Vulcanologia) and TAS-I (Thales Alenia Space - Italy) were put together in this work of assessment. ISIS Team proposed new experimental facilities of the Galileo satellites, designed to realize inter-satellite and in situ measurements to monitor global and local quantities; in particular, a scalable system of Langmuir probes was suggested, while the TEC along all possible inter-satellite ray paths throughout the plasmasphere could be monitored via phase- and group-delay analysis of inter-satellite radio signals.Published1A. Geomagnetismo e Paleomagnetismo2A. Fisica dell'alta atmosferaN/A or not JCRope

The ISIS Project: Indications for Future Near-Earth Plasma Studies through Future Galileo Satellites

The Earth’s plasmasphere variability is a consequence of the Sun’s forcing, determining our planet’s space weather. Plasmaspheric dynamics could be entirely caught only by studying together global and local proxies of the state of this extended system. The ISIS project (Inter-Satellite & In Situ plasmaspheric monitoring and modelling) aimed to design a system for the continuous monitoring of the Earth’s plasmasphere based on the future Galileo satellites. The efforts and expertise of ISC-CNR (Institute for Complex Systems of the National Research Council of Italy), INGV (Istituto Nazionale di Geofisica e Vulcanologia) and TAS-I (Thales Alenia Space - Italy) were put together in this work of assessment. ISIS Team proposed new experimental facilities of the Galileo satellites, designed to realize inter-satellite and in situ measurements to monitor global and local quantities; in particular, a scalable system of Langmuir probes was suggested, while the TEC along all possible inter-satellite ray paths throughout the plasmasphere could be monitored via phase- and group-delay analysis of inter-satellite radio signals

Ionosphere modelling for Galileo single frequency users: illustration of the combination of the NeQuick model and GNSS data ingestion

The ionospheric effect remains one of the main factors limiting the accuracy of Global Navigation Satellite Systems (GNSS) including Galileo. For single frequency users, this contribution to the error budget will be mitigated by an algorithm based on the NeQuick global ionospheric model. This quick-run empirical model provides flexible solutions for combining ionospheric information obtained from various sources, from GNSS to ionosondes and topside sounders. Hence it constitutes an interesting simulation tool not only serving Galileo needs for mitigation of the ionospheric effect but also widening the use of new data. In this study, we perform slant TEC data ingestion - the optimisation procedure underlying the Galileo single frequency ionospheric correction algorithm - into NeQuick for a dozen locations around the world where both an ionosonde and a GPS receiver are installed. These co-located instruments allow us to compare measured and modelled vertical TEC showing for example global statistics or dependence towards latitude. We analyse measurements for the year 2002 (high solar activity level) giving an insight into the situation we could observe when Galileo reaches its Full Operation Capability, during the next solar maximum. At last we compare Galileo and GPS ionospheric corrections. For Galileo, we end up with an underestimation of 11% and 4% depending on the version of NeQuick embedded in the algorithm, as well as a 22% standard deviation. This means respectively twice, five and 1.5 times better than GPS

Measurement and Modeling of the Aeronautical Channel for Galileo

Power, delay and bandwidth of reflections at aircraft structures are not modelled accurate enough for new GNSS signal structures. For that reason ESA commissioned a contract about a measurement campaign in 2002. Only reflections which arrive shorter than the chip duration mainly contribute to the positioning error of a navigation receiver. This nature of the system made it necessary to measure the channel with an extremely high bandwidth of 100MHz, which results in a time resolution of 20ns, enhanced down to 1ns by using a super-resolution algorithm. The most important scenario for this channel type is the final approach. In the experiment we used an aircraft (Pilatus Porter) as the transmitting platform. The receiver was mounted in the 25m span experimental jet VFW-614 approaching Thalerhof airport of Graz/Austria. In a second step a helicopter as transmitter circled the parked VFW-614, while reflections on the plane were measured. To allow extensions of the measurements to larger aircrafts, the ground measurements were repeated with an Airbus A340. Evaluating the measurement data we were able to disprove the existence of a significant wing reflection. Due to the large bandwidth of the measurement we have been able to detect and model a strong, short delayed reflection on the fuselage, whose narrow bandwidth makes it nearly impossible to suppress its influence by averaging. As second contribution to the multipath channel the ground reflection was detectable. It was modulated by the changing terrains reflectivity and was Doppler shifted according to the aircrafts movement. We were able to correlate the Doppler shift with the sink rate. This achievement was used to model the ground echo properly. To gain more precise results, physical optics simulation was used to verify the measurements and proof the existence of the fuselage echo. We will present channel models for both aircrafts

Measurements and modeling of the satellite-to-indoor channel for Galileo

In this paper we present results obtained during an ESA project in 2002, carried out by Joanneum Research/Austria, DLR/Germany and the University of Vigo/Spain. Measurements were performed using a high resolution channel sounder on board a helicopter, the objective being the characterization of the satellite-to-indoor channel at frequencies close to those assigned to the future Galileo system. The helicopter flew around a building at different elevations. The receiver was placed in different locations within the building so that different penetration conditions were studied. Typical measured power-delay profiles will be presented and analyzed. To complement the study, a 3D CAD model of the measurement building was created to be used by a deterministic ray-tracing based propagation tool to gain further insight on the propagation phenomena. The external and internal walls as well as windows and doors and features like staircases were considered in the CAD model. Different materials and wall widths were also assumed. The ray-tracing tool included a Uniform Geometrical Theory of Diffraction, UGTD, electromagnetic module. Contributions of second order reflections and diffractions were taken into account, characterized in terms of magnitude, phase, delay and angle of arrival, being later converted to power-delay profiles. It has been confirmed that wall attenuation is the main propagation element, which drastically reduces in-building coverage, except for rooms with external walls. For these external wall rooms and hallways the consideration of diffracted rays is essential to make the predictions match the measurements. A statistical channel model was derived from the measurements and the deterministic ray-tracing analysis. It reflects the different time-spreading conditions found in the measurements, which are mainly caused by reflections and diffractions within the building itself and those produced on external buildings. The statistical model also addresses how the arriving contributions reach the receiver in groups or clusters of rays