High Accuracy GNSS Based Navigation in GEO

Although significant improvements in efficiency and performance of communication satellites have been achieved in the past decades, it is expected that the demand for new platforms in Geostationary Orbit (GEO) and for the On-Orbit Servicing (OOS) on the existing ones will continue to rise. Indeed, the GEO orbit is used for many applications including direct broadcast as well as communications. At the same time, Global Navigation Satellites System (GNSS), originally designed for land, maritime and air –applications, has been successfully used as navigation system in Low Earth Orbit (LEO) and its further utilization for navigation of geosynchronous satellites becomes a viable alternative offering many advantages over present ground based methods. Following our previous studies of GNSS signal characteristics in Medium Earth Orbit (MEO), GEO and beyond, in this research we specifically investigate the processing of different GNSS signals, with the goal to determine the best navigation performance they can provide in a GEO mission. Firstly, a detailed selection among different GNSS signals and different combinations of them is discussed, taking into consideration the L1 and L5 frequency bands, and the GPS and Galileo constellations. Then, the implementation of an Orbital Filter is summarized, which adaptively fuses the GNSS observations with an accurate orbital forces model. Finally, simulation tests of the navigation performance achievable by processing the selected combination of GNSS signals are carried out. The results obtained show an achievable positioning accuracy of less than one meter. In addition, hardware-in-the-loop tests are presented using a COTS receiver connected to our GNSS Spirent simulator, in order to collect real-time hardware-in-the-loop observations and process them by the proposed navigation module.

High accuracy GNSS based navigation in GEO

Paul David Blunt, Cyril Botteron, Vincenzo Capuano, Pierre-André Farine, Endrit Shehaj

Although significant improvements in efficiency and performance of communication satellites have been achieved in the past decades, it is expected that the demand for new platforms in Geostationary Orbit (GEO) and for the On-Orbit Servicing (OOS) on the existing ones will continue to rise. Indeed, the GEO orbit is used for many applications including direct broadcast as well as communications. At the same time, Global Navigation Satellites System (GNSS), originally designed for land, maritime and air applications, has been successfully used as navigation system in Low Earth Orbit (LEO) and its further utilization for navigation of geosynchronous satellites becomes a viable alternative offering many advantages over present ground based methods. Following our previous studies of GNSS signal characteristics in Medium Earth Orbit (MEO), GEO and beyond, in this research we specifically investigate the processing of different GNSS signals, with the goal to determine the best navigation performance they can provide in a GEO mission. Firstly, a detailed selection among different GNSS signals and different combinations of them is discussed, taking into consideration the L1 and L5 frequency bands, and the GPS and Galileo constellations. Then, the implementation of an Orbital Filter is summarized, which adaptively fuses the GN1SS observations with an accurate orbital forces model. Finally, simulation tests of the navigation performance achievable by processing the selected combination of GNSS signals are carried out. The results obtained show an achievable positioning accuracy of less than one meter. In addition, hardware-in-the-loop tests are presented using a COTS receiver connected to our GNSS Spirent simulator, in order to collect real-time hardware-in-the-loop observations and process them by the proposed navigation module

Elsevier2017

GNSS-based Orbital Filter for Earth Moon Transfer Orbits

Cyril Botteron, Vincenzo Capuano, Pierre-André Farine

Cambridge University Press2015

GNSS-Based Navigation for Lunar Missions

Vincenzo Capuano

Numerous applications, not only Earth-based, but also space-based, have strengthened the interest of the international scientific community in using Global Navigation Satellite Systems (GNSSs) as navigation systems for space missions that require good accuracy and low operating costs. Indeed, already used in Low Earth Orbits (LEOs), GNSS based-navigation GNSS-based navigation systems can maximize the autonomy of a spacecraft while reducing the costs of ground operations, allowing for budget-limited missions of micro- and nanosatellites. This is why GNSS is also very attractive for applications in higher Earth orbits up to the Moon, such as in Moon Transfer Orbits (MTOs). However, while GNSS receivers have already been exploited with success for LEOs, their use in higher Earth orbits above the GNSS constellation is extremely challenging, particularly on the way from the Earth to the Moon, characterized by weaker signals with wider gain variability, larger dynamic ranges resulting in higher Doppler and Doppler rates, critically lower satellite signal availability, and poorer satellite-to-user geometry. In this context, the first research objective and achievement of this PhD research is a feasibility study of GNSS as an autonomous navigation system to reach the Moon, and the determination of the requirements for the design of a code-based GNSS receiver for such a mission. The most efficient combinations of signals transmitted by the GPS, Galileo, and combined GPS-Galileo constellations have been identified by analyzing the theoretical achievable signal acquisition and tracking sensitivities, the resultant constellation availability, the pseudorange error factors, and the geometry error factor and accordingly the achievable navigation performance The results show that GNSS signals can be tracked up to Moon altitude, but not with the current GNSS receiver technology for terrestrial use. The second research objective and achievement is the design and implementation of a GNSS receiver proof-of-concept capable of providing GNSS observations onboard a space vehicle orbiting up to Moon altitude. This research work describes the hardware architecture, the high-sensitivity acquisition and tracking modules and the standalone single-epoch navigation performance of the developed GPS L1 C/A hard-ware receiver, named the WeakHEO receiver. Although they can still be collected, GNSS observations at Moon altitude, if not filtered, but simply used to compute a single-epoch least-squares solution, lead to a very coarse navigation accuracy, on the order of 1 to 10 km, depending on the number and type of signals successfully processed. Therefore, the third and main research objective and achievement is the design and implementation of a GNSS-based orbital filter (OF) determination unit, based on an extended Kalman filter (EKF) and an orbital forces model, able to significantly improve the achievable navigation performance and also to aid acquisition and tracking modules of the GNSS receiver. Simulation results of the OF performance when processing simulated GPS and Galileo observations, but also real GPS L1 C/A observations provided by the WeakHEO receiver (when connected in a hardware in the loop configuration to a full constellation GNSS radio frequency signal simulator), show a positioning accuracy at Moon altitude of a few hundred meters.

EPFL2016

GNSS-Based Navigation for Lunar Missions

Vincenzo Capuano

EPFL2016