Relative GPS Navigation for an Automated Rendezvous Docking Test Satellite ETS-VII

Isao Kawano, Masaaki Mokuno, Toru Kasai

Abstract:	The National Space Development Agency of Japan (NASDA) has conducted research on unmanned Rendezvous Docking (RVD) technology since 1970s. RVD technology is an essential for developing the unmanned H-II Orbiting Plane (HOPE), the H-II Transfer Vehicle (HTV), the Orbital Servicing Vehicle (OSV), and lunar and mars explorers, which will perform various space activities. An in-orbit demonstration projeet of the unmanned automated RVD system using the Engineering Test Satellite-VII (ETS-VII) is now under way. ETS-VII consists of two satellites, a “chaser” and a “Target” as shown in Figure 1. The Chaser releases the Target and performs an RVD experiment. For an unmanned space vehicle to perform automated RVD, a navigation function for measuring and estimating the relative position and veloeity between the chaser and the Target is needed. ETS-VII has three types of navigation methods, which are used in turn based on the distance between the Chaser and the Target. Relative GPS navigation, which is a sort of differential GPS (DGPS), is used primarily from 500m to 9km. Both satellites have GPS reeeivers, and they receive signals transmitted by the same GPS satellites. Pseudoranges and delta-ranges measured by the Target GPS receiver (T/GPSR) are sent to the Chaser GPSR (C7GPSR) via an inter-satellite communication link between the chaser and the Target (C-T communication link). The C/GPSR then processes the data measured by both satellites’ GPSRS, and estimates their relative position and velocity by using an Extended Kalman Filter (EKF). In this paper, we will introduce the ETS-VII RVD experiment plan and its RVD system.. Next, we will present the ETS-VII relative GPS navigation system design including GPSR hardware and software, and the C-T communication link. Before launch, navigation performance should be verified by ground tests. The result of protoflight test will also be reported in a later section.
Published in:	Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997) September 16 - 19, 1997 Kansas City, MO
Pages:	707 - 715
Cite this article:	Kawano, Isao, Mokuno, Masaaki, Kasai, Toru, "Relative GPS Navigation for an Automated Rendezvous Docking Test Satellite ETS-VII," Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997), Kansas City, MO, September 1997, pp. 707-715.
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