Mass-Market Receiver for Static Positioning: Tests and Statistical Analyses

Nowadays, there are several low cost GPS receivers able to provide both pseudorange and carrier phase measurements in the L1band, that allow to have good realtime performances in outdoor condition. The present paper describes a set of dedicated tests in order to evaluate the positioning accuracy in static conditions. The quality of the pseudorange and the carrier phase measurements let hope for interesting results. The use of such kind of receiver could be extended to a large number of professional applications, like engineering fields: survey, georeferencing, monitoring, cadastral mapping and cadastral road. In this work, the receivers performance is verified considering a single frequency solution trying to fix the phase ambiguity, when possible. Different solutions are defined: code, float and fix solutions. In order to solve the phase ambiguities different methods are considered. Each test performed is statistically analyzed, highlighting the effects of different factors on precision and accurac

A Dense Reference Network for Mass-Market Centimeter-Accurate Positioning

The quality of atmospheric corrections provided by a dense reference network for centimeter-accurate carrierphase differential GNSS (CDGNSS) positioning is investigated. A dense reference network (less than 20 km inter-station distance) offers significant benefits for mass-market users, enabling lowcost (including single-frequency) CDGNSS positioning with rapid integer ambiguity resolution. Precise positioning on a massmarket platform would significantly influence the world economy, ushering in a host of consumer-focused applications such as globally-registered augmented and virtual reality and improved all-weather safety and efficiency for intelligent transportation systems, applications which have so far been hampered by the several-meter-level errors in standard GNSS positioning. This contribution examines CDGNSS integer ambiguity resolution performance in terms of network correction uncertainty, and network correction uncertainty, in turn, in terms of network density. It considers the total error in network corrections: a sum of ionospheric, tropospheric, and reference station multipath components. The paper’s primary goal is to identify the network density beyond which mass-market users would see no further significant improvement in ambiguity resolution performance. It finishes by describing development and deployment of a low-cost dense reference network in Austin, Texas.Aerospace Engineering and Engineering Mechanic

Space User Visibility Benefits of the Multi-GNSS Space Service Volume: An Internationally-Coordinated, Global and Mission-Specific Analysis

The number and scope of Global Navigation Satellite System (GNSS)-based space applications has grown significantly since the first GNSS space receiver was flown in the early 1980's. The vast majority of GNSS space users operate in Low-Earth Orbit (LEO), where the use of GNSS receivers has become routine. However, the use of GNSS has expanded to other orbit regimes like Geostationary Orbits (GEO) and High Eccentric Orbits (HEO) but has been very limited due to the challenges involved. The major challenges for such types of orbits including much weaker signals, reduced geometric diversity, and limited signal availability. In any case, considering the recent development of multiple GNSS constellations and ongoing upgrades to existing constellations, GNSS signal availability will improve significantly. As a result, this expanded multi-GNSS signal capability will enable improved on-orbit navigation performance and will also allow the development of new mission concepts. High altitude space users will especially benefit from this evolution, which will provide GNSS signals to challenging regimes well beyond Low Earth Orbit. These benefits will only be realised, however, if additional signals are designed to be interoperable, are clearly documented and supported. In order to enhance the overall GNSS performance for spacecraft's in regimes from LEO, GEO to HEO and beyond, all Satellite Navigation constellation providers and regional augmentation system providers are working together through the United Nations International Committee on GNSS (ICG) forum to establish an interoperable GNSS Space Service Volume (SSV) for the benefit of all GNSS space users. This paper provides an overview of the technical work and in particular the simulations, performance analysis and discussions of the outcomes and results obtained by the UN ICG Working Group-B in the context of the GNSS Space Service Volume activities, which were supported by all GNSS service providers

Global Navigation Satellite System Performance in Cislunar Space for Cubesat Form Factors

An increased Cislunar traffic is expected by the end of this decade stemming from NASA’s Artermis program. Given the prioritization limitations of the Deep-Space Network (DSN) for ranging and tracking of increased deep- space assets, a more viable, and cost effective, independent navigation capability is needed. NASA’s 2015 Navigator Global Positioning System (GPS) deployed on the Magnetospheric Multi-Scale (MMS) spacecraft has validated the feasibility of acquiring weak GPS signals at distances up to 25 Earth Radii (~150,000km) or about 40% of the Cislunar trajectory. NASA plans to upgrade the flight proven MSS Navigator GPS for the future Lunar Gateway. Concurrently, the European Space Agency has confirmed the feasibility of an interoperable GPS and Galileo receiver at Lunar altitudes for a low acquisition and tracking threshold “Weak HEO” receiver for a Cubesat platform. This engineering analysis sets out to explore: (1) the smallest Global Navigation Satellite Systems (GNSS) receiver antenna that can ensure a positive carrier and code link for a Lunar bound Cubesat; (2) the position dilution of precision (PDOP) profile of this Lunar bound space vehicle; and (3) the expected improvement of the PDOP during the Moon Transfer Orbit (MTO) for an interoperable GNSS receiver, specifically Beidou. For the designed carrier-to-noise acquisition and tracking threshold of 15 dBHz, the Eb/N0 link was assured for a helix antenna with a minimum diameter of 130 mm and length of 200 mm for the GPS L1 frequency at a data rate of 50 bps. The Galileo E5a, E5b would require a larger diameter antenna at 760 mm at 448 bps data rate while Beidou requires a 350 mm diameter antenna for a 100 bps data rate to close their respectively. Utilizing the 130 mm diameter, 200 mm length helix antenna on a Lunar MTO, the preliminary assessment indicated that the GNSS PDOP calculated from valid carrier links increases from 20 when the vehicle is within the GNSS service volume to several 100th or 1000th at 60.3 Earth Radii. Due to their similar constellation altitude geometry, the Galileo E5b PDOP growth profile is similar to that of the GPS L1. The Beidou system however has a much lower PDOP growth. This difference is attributed to the set of Beidou Geosynchronous space vehicles (SV)s that have greater angular separation to the SV- receiver line-of-sight (LoS). For an interoperable GNSS receiver that can track the GPS, Galileo, and Beidou lower bound and upper bound frequencies simultaneously, the increased number of valid signals reduces the PDOP growth below 200. This engineering analysis re-affirms the potential of utilizing existing GNSS infrastructure for onboard navigation in Cislunar space, in particular, a helical antenna that can be accommodated on a Cubesat form factor

Evaluation of advanced receiver autonomous integrity monitoring performance on predicted aircraft trajectories

The development of new GNSS constellations, and the modernization of existing ones, has increased the availability and the number of satellites-in-view, paving the way for new navigation algorithms and techniques. These offer the opportunity to improve the navigation performance while at the same time potentially reducing the support which has to be provided by Ground and Satellite Based Augmented Systems (GBAS and SBAS). These enhanced future capabilities can enable GNSS receivers to serve as a primary means of navigation, worldwide, and have provided the motivation for the Federal Aviation Administration (FAA) to form the GNSS Evolution Architecture Study (GEAS). This panel, formed in 2008, investigates the new GNSS-based architectures, with a focus on precision approach down to LPV-200 operations. GEAS identified ARAIM as the most promising system. The literature, produced through a series of studies, has analysed the performance of this new technique and has clearly shown that the potential of ARAIM architectures to provide the Required Navigation Performance for LPV 200. Almost all of the analysis was performed by simply studying a constellation’s configuration with respect to fixed points on a grid on the Earth’s surface, with full view of the sky, evaluating ARAIM performance from a geometrical point of view and using nominal performance in simulated scenarios lasting several days In this paper, we will evaluate the ARAIM performance in simulated operational configurations. Aircraft flights can last for hours and on-board receivers don’t always have a full view of the sky. Attitude changes from manoeuvers, obscuration by the aircraft body and shadowing from the surrounding environment could all affect the incoming signal from the GNSS constellations, leading to configurations that could adversely affect the real performance. For this reason, the main objective of the algorithm developed in this research project is to analyse these shadowing effects and compute the performance of the ARAIM technique when integrated with a predicted flight path using different combinations of three constellations (GPS, GLONASS and Galileo), considered as fully operational

Performance Assessment of Navigation Using Carrier Doppler Measurements from Multiple LEO Constellations

The goal of this work is to characterize a novel navigation method which uses carrier Doppler shift measurements from LEO satellites. An ever-growing reliance on the GNSS has coincided with an increase in ways it can be degraded or denied, whether naturally occurring or man-made. These potentially disastrous threats to traditional navigation and timing have necessitated new technologies to augment GNSS in the case of an outage. LEO constellations, whose size and higher signal power make them potentially useful for navigation, are one technology that has been explored. The navigation algorithms detailed in this research use Doppler measurements from 8 or more LEO satellites to simultaneously solve for position, clock offset, velocity, and clock offset rate. Through simulation, a user-satellite geometry analysis is conducted for a number of emerging LEO constellations, as well as navigation simulations with the same constellations. Results are presented which show promise from both a satellite geometry perspective and PVT solution convergence perspective

ARAIM for Vertical Guidance Using GPS and BeiDou

An advanced Receiver Autonomous Integrity Monitoring (ARAIM) approach is investigated when augmenting GPS satellites with the current regional BeiDou constellation. A procedure for integrity monitoring, including checking its availability, fault detection and exclusion, and integrity testing is presented. Fault modes and their probabilities using GPS and GPS+BeiDou are discussed. Testing of ARAIM for vertical guidance using real data in eight sites distributed globally (Australia, China, Netherlands, eastern Canada and Peru) show that the addition of the BeiDou constellation, despite the decreased preliminary confidence placed in its performance compared with GPS, results in a substantial improvement to ARAIM availability performance and a higher level of integrity, in particular at sites observing all of its current constellation (Australia and China). The improvement was less in sites that can only observe some or no GEO and IGSO satellites (Netherlands, Canada and Peru). However, the benefit of adding BeiDou to GPS at these sites is expected to substantially improve with full deployment of MEO satellites

LION Navigator for Transfer to GEO Using Electric Propulsion

GNSS space receivers are widely used for onboard auton-omous navigation of spacecraft platforms in low Earth orbit. Navigation by GNSS up to geosynchronous altitude was made possible through the introduction of a Space Service Volume which defines signal strength up to geo-synchronous altitude. For Galileo, similar definitions are under consideration. On this basis onboard autonomous navigation for commercial communication satellites be-came a realistic possibility, too. Transfer to geostationary orbit is still fully depending on classical RF tracking by ground station for orbit determination. With electrical propulsion, the transfer duration extends to several months. As a consequence onboard autonomous naviga-tion by satellite navigation has become of commercial interest. A GNSS navigation receiver on a spacecraft on transfer orbit has to cope with extreme signal conditions from very low (at perigee) to very high (at super-synchronous apogee) altitude, which is far above the constellation satellites. At this altitude only very rare and weak signals that spill over the limb of the earth can be used. An addi-tional difficulty is the varying spacecraft orientation which is not nadir pointing, as is commonly assumed, but is varying according to the demands of optimal attitude guidance laws and power requirements. By using both GPS and Galileo together the availability of navigation signals is increased. The paper describes the design process to determine basic parameters e.g. number and orientation of receive anten-nas, receiver parameters like C/N0 thresholds, and naviga-tion procedures. Detailed simulations are presented for selected parts of the transfer arc using verified models of the navigation receiver. Finally the geostationary transfer capabilities of the space-borne LION Navigator GNSS receiver are demon-strated in a closed-loop real time test environment under RF stimulation