Masaaki Mokuno

Result of Autonomous Rendezvous Docking Experiment of Engineering Test Satellite-VII

On 7 July 1998, Engineering Test Satellite-VII (ETS-VII) successfully performed the e rst autonomous rendezvous docking (RVD) between uninhabited spacecraft ever. RVD technology is essential for future space activities, such aslogisticsupportfortheInternational SpaceStation.TheNationalSpaceDevelopment Agency ofJapan developed ETS-VII to demonstrate autonomous RVD technologies. ETS-VII carried two RVD experiment e ights successfully in 1998. We introduce the autonomous RVD system of ETS-VII and show the results and evaluations of two RVD experiment e ights. We realized autonomous uninhabited RVD, and its performance was better than required.

In-orbit demonstration of rendezvous laser radar for unmanned autonomous rendezvous docking

The National Space Development Agency of Japan (NASDA) performed unmanned autonomous rendezvous docking (RVD) experiments using the Engineering Test Satellite VII (ETS-VII) in 1998 and 1999. In these experiments, a rendezvous laser radar (RVR) was used as the primary navigation sensor during the final approach phase (relative distances from 500 m to 2 m). The RVR functioned properly, and its characteristics, which are measurement accuracy, optical propagation, and acquisition/tracking, satisfied the requirements. The experimental results show that RVR is effective for autonomous rendezvous docking.

Result of Rendezvous Docking Experiment of ETS-VII.

ETS–VII is a test satellite to perform in-orbit demonstration of autonomous rendezvous docking (RVD) technology, which will be necessary for advanced space activities in the early 21st century. ETS–VII performed three RVD experiment flights, and verified all technical items. ETS–VII demonstrated first autonomous RVD between unmanned vehicles, and remote piloted rendezvous flight position accuracy at docking was about 1cm, and acceleration was less than 1.5mG (low impact docking). In the second RVD experiment flight, ETS–VII detected attitude anomaly and executed disable abort for safety insurance. We present the results and evaluation of three RVD experiment flights in this paper.

Development of the rendezvous radar for the Engineering Test Satellite VII

This paper describes the functions and performance of the rendezvous radar (RVR) developed for the rendezvous docking experiment system of Engineering Test Satellite VJJ (ETS-VJI). The RVR measures line of sight angle and distance between the chaser satellite and the target satellite of ETS-VJJ with low power consumption at high processing speed. These advanced features were realized by adopting dual mode intensity modulation of laser beam and embedded image recognition algorithm. The heritage of the development will be used for rendezvous docking system of future space transportation systems.

ESD Ground Test of ITO-Coated Back Surface of Solar Paddle for a Polar Satellite

Optical Inter-orbit Communications Engineering Test Satellite (OICETS) carried the thermal control films with ITO coating that was not explicitly connected to satellite body ground. This coating might be charged negatively by aurora electron. Laboratory experiments were carried out to investigate charging and arcing phenomena on the back surface of solar paddle that have bypath and blocking diodes. We irradiate test coupon with an electron beam to simulate charging situation of wake region. The ITO coatings with the vent holes were charged up to -200V though the irradiated electron beam current was 1000 times larger than nominal aurora electron current. Because the electric resistance between the ITO coatings and paddle substrate was about MΩ ~ GΩ due to the vent holes. It was confirmed that ITO-coated back surface of solar paddle which connected to substrate with low resistance was effective to suppress charging by aurora electrons for polar satellites. Also, no catastrophic discharge was occurred through one hundred primary arcs expected on the orbit. Such perfect durability was accomplished by covering the entire conductive surface of power line such as diode terminal or wire harness by tubes and adhesive. This design is effective measures to all satellites.

GPS relative navigation system for space use

A GPS relative navigation system, used for rendez-vous in space, is introduced. This system was designed for the experiment of unmanned rendez-vous docking of ETS-VII (Engineering Test Satellite VII), which consists of a target satellite and a chaser satellite, planned to be launched in November,1997, has been developed. Newly developed four GPS Receivers (GPSRs), two on the chaser satellite and two on the target satellite, are used in this system. The relative navigation system outputs navigation results with the accuracy of 10m (position) and 2cm/sec(velocity). Tests of the system including thermal vacuum test, vibration tests and performance test had been carried out for 3 months. 8-hour and 9-hour scenarios along to ETS-VIFs rendez-vous flight paths were employed in the performance test. The system was qualified as a space system through the tests.

Guidance, Navigation and Control System in Engineering Test Satellite VII Rendez-Vous and Docking Experiment

Abstract Rendez- Vous & Docking(RVD) is an indispensable technology for future space activities. Its first flight demonstration is scheduled in 1997 as an experiment of Engineering Test Satellite VII (ETS-VII). In this paper, Guidance, Navigation and Control (GN&C) System, which is the key technology to realize ETS-VII RVD mission, and its related development items are presented.