: Japan has been investigating the use of an airship system that will function as a stratospheric platform (SPF) for applications such as environmental monitoring, communications and broadcasting. If pseudolites were mounted on the platforms, their GPS-like signals would be stable augmentations that would improve the accuracy, availability, and integrity of GPS-based positioning systems because the airship network would cover all of Japan. The accuracy of the pseudolite positions would be a limiting factor for such a service since the pseudolite 'ephemeris error' is more serious than GPS due to the lower height of the platform. In this paper, a conceptual design of the SPF-based augmentation system is first introduced. Then some schemes for estimating the pseudolite position are described.
The benefits of combined use of the GLONASS and GPS navigation satellite constellations have become obvious for applications such as open-cast mining operations and highly dynamic vehicles such as spaceplanes. Moreover, using GLONASS satellites in addition to GPS is useful for long baseline applications since it increases the numbers of satellites in common view. Japan's National Aerospace Laboratory (NAL) has been conducting feasibility studies using combined GPS/GLONASS positioning for spaceplane landing systems and the precise navigation of stratospheric airships. This paper presents the results of the first Japanese kinematic GPS/GLONASS flight test. In the test, the difference in estimated position between dual frequency GPS and single frequency GPS/GLONASS systems was found to be within a few centimeters, indicating that GLONASS carrier phase ambiguities were correctly resolved. To demonstrate the benefits of combining GLONASS with GPS navigation, an on-the-fly (OTF) test of instantaneous ambiguity resolution with a 30 degree cutoff angle was performed. The OTF performance of the combined GPS/GLONASS system was found to be similar to that of a GPS system with a cutoff angle of 10 degrees, showing that augmentation of GPS with GLONASS will be useful for highly dynamic vehicle applications.
SUMMARYThis paper proposes a method for identifying the modal parameters of large space structures and estimating their attitude and deformation using kinematic GPS. The Eigensystem Realization Algorithm method is used for the modal parameter identification, and for attitude and deformation estimation, we adopt the Kalman filter based on the identified system dynamics. The proposed method was evaluated through computer simulations and in groundbased experiments, and the results confirmed its feasibility.
NAL and NASDA develop High Speed Flight Demonstrators (HSFDs) to examine an automatic takeoff and landing technology (Phase 1) and to measure the transonic aerodynamic characteristics of a reusable space plane for getting the reference data of a CFD (Computational Fluid Dynamics) technology (Phase 2). As a HSFD navigation sensor, we develop GPS Aided Inertial Navigation Avionics (GAIA) whose distinctive feature is the usage of the carrier-phase DGPS (CDGPS)/INS hybrid navigation technology. This paper describes the design of GAIA. We show its accuracy, integrity, continuity and then availability performances that are analyzed by numerical simulations, which we first developed. Ground and flight tests are also carried out to confirm the performance of the GAIA flight model. Both results prove that GAIA meets the requirements of the navigation performance even under the severe flight conditions of HSFD.
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