Yasufumi Nagai

Preliminary experiments on technologies for satellite orbital maintenance using Micro-LabSat 1

For maturation of space activities, not only developing and using space systems is important, but also performing maintenance on them in their orbital environment is necessary in order to use them efficiently. The Communications Research Laboratory (CRL) has been studying an orbital maintenance system (OMS), specifically an on-orbit satellite maintenance system. An important first step is the capability to autonomously recognize and rendezvous with a target satellite. The CRL developed a microprocessor multi-chip module to control the OMS, including its robotic system and image processing, and installed it on Micro-LabSat for a mission called Micro-OLIVe (MicroLabSat was developed by NASDA and launched in 2002 together with the environment observation technology satellite ADEOS-II). In this paper, we describe the OMS concept, our experimental system and results of the Micro-OLIVe experiments. These experiments aimed at using the microprocessor multi-chip module to control the OMS, its camera units that use conventional C-MOS digital still cameras and its software used for flexible image processing.

Single-event performance of COTS-based MPU under flare and nonflare conditions

We investigated the in-orbit performance of a high-performance on-board computer developed with commercial off-the-shelf (COTS) technology in terms of its performance during the occurrence of single event effects. The processor worked and performed successfully both under normal and under solar flare conditions in 800 km altitude polar orbit. During a solar flare, the occurrence of single events increased by a factor of more than four compared with normal conditions. The area where single events occurred during the solar flare spread to the polar region, whereas normally they are limited to the region of South-Atlantic anomalies (SAA). Our results suggest that the performance of our COTS processor is sufficient for future space applications.

Mechanism for assembling antenna in space

The development of large and precise space antennas is one of the most important topics in constructing space infrastructures. We evaluated an approach to assembling large and accurate space antennas which uses space robots. The assembly mechanism was launched together with the ETS-VII, the first telerobotic satellite from Japan, and its performance, including fully automatic assembling, was verified. The assembling-type antenna and the results of antenna assembly experiments are discussed.

Teleoperation system for antenna assembly by space robots

Antenna assembly by space robots is an effective method for producing large antennas in space and it offers several advantages over using inflatable antennas and deployable antennas. The Communications Research Laboratory has developed such assembled antennas as a means to produce large space antennas, and the first on-board experiments were performed on Engineering Test Satellite VII, which was launched in 1997. In this paper, we outline the antenna- assembly experiments on ETS-VII and present initial experiments results.

Audio feedback system for teleoperation experiments on engineering test satellite VII system design and assessment using eye mark recorder for capturing task

When operating space robots, safety and reliability are the most important issues-even at the expense of dexterity and swiftness. This makes it very stressful for operators to teleoperate space robots, especially since they cannot be repaired during operation, unlike ground robots. Furthermore, operators have to quickly analyze a large amount of information about the target objects and immediately make decisions on how to proceed. The majority of this information is presented visually, including digital values, status displays, 3D computer simulation, and camera images. Therefore, we developed an audio feedback system that can convey some of this information in order to improve the operators decision-making and avoid accidents. We used an eye-mark-recorder to assess the performance of this system. Audio systems for information presentation have previously only been proposed for ground-based operation systems. This is the first case in which sound has been utilized for space robot operation, even though sound does not actually exist in space.

Approach for on-orbit maintenance and experiment plan using 150kg-class satellites

With the maturation of space technology, there is an increasing focus on the maintenance of space craft and the space environment. NICT (National Institute of Information and Communications Technology) has proposed an Orbital Maintenance System (OMS), which is a rescue-and-removal satellite-servicing system for telecommunications satellites, and has conducted research on related technologies. One of the biggest challenges in on-orbit maintenance is the development of autonomous rendezvous technologies. The rescue satellite must be able to approach the target satellite before it falls out of orbit. Meanwhile NICT and Mitsubishi Heavy Industries (MHI) have been planning a unique small-satellite mission called SmartSat-1. Using SmartSat-1, NICT and MHI are planning to carry out experiments on autonomous rendezvous technologies for the OMS. In this paper, we describe the next demonstration mission for the orbital maintenance system, which will utilize the 150-kg class twin-sat, SmartSat-1

Audio feedback system for engineering test satellite VII

An efficient and reliable interface to manage telemetry information is most important in the teleoperation of space robots. Operators need to be able to recognize and verify large amounts of telemetry information quickly and accurately. Visual information around the workspace of space robots is very limited, and the detailed position of work is uncertain. These difficulties raise the load on operators. We have been running experiments on assembling antennas using the Engineering Test Satellite VII (ETS-VII), so we are very much aware of the need for an effective man-machine interface to handle telemetry information. We have developed an audio interface system for the efficient operation of ETS-VII. Unlike a visual interface, this audio interface allows an operator to (1) perceive information even if pay small attention for it, and (2) easily identify trends and changes. The system analyzes telemetry information in real- time, and converts changes in the status of information into voice data, and changes in the magnitude of forces into the frequency of motor noise. The effectiveness of this audio interface was verified in operations of ETS-VII by monitoring eye movements over time. Time is measured by the mean interval between status changes and command submissions. An eye mark recorder records eye movements. The data suggests significant effects of the audio interface system.

On-orbit performance demonstration of terrestrial processor for orbital maintenance system on the Micro-LabSat

We describe the experimental system and some preliminary experimental results for the Micro-OLIVe mission launched in 2002. An important first step in developing an orbital maintenance system (OMS) is to autonomously recognize and rendezvous with a target satellite. The Communications Research Laboratory developed a microprocessor multi-chip module to control the OMS, including a robotic system and image processing system, and installed them on Micro-LabSat for a mission called Micro-OLIVe. The microprocessor and inspection camera using commercial-off-the-shelf (COTS) CMOS imaging units exhibited adequate performance, showing the feasibility of using low-cost COTS equipment.

Difference in the effects of an audio feedback system for difference in operation task and skill level of human operators in experiments of ETS-VII

We used an Audio Feedback System (AFS) to present some telemetric data to human operators, as auditory information in robot arm experiments with Engineering Test Satellite VII (ETS-VII). Our intention was to provide information that assists in easier and safer operation. We think that the human-machine interface presented to human operators should correspond to different tasks and to different skill levels of human operators. Fortunately, we had opportunity to assess AFS for two tasks those of a Commander and Monitor. The Commander operates the robot arm by transmitting tele- operation commands, while the Monitor checks the indications of telemetric data on a status display. During the experiment, the Commander and Monitor used a status display to check information on the robot arm. In the experiments, seven human operators, four Commanders and three Monitors, performed their respective tasks. In order to assess the effectiveness of AFS for various skill levels of human operators, an astronaut who has a very high level of skill in controlling the robot arm was included among the Monitors. In determining the effectiveness of AFS, we focuses on the eye movements of human operators. We thus used an eye mark recorder (EMR) to measure eye movements. When auditory information was given, average fixation times required to confirm telemetric data indicated on the status display were shortened except in the case of the astronaut. AFS had no effect on the astronauts performance.

Comparison between the astronaut and standard operators as telemetry monitor for effects of audio feedback system in the operation of the Engineering Test Satellite VII

It is the most important that we perform safe and reliable teleoperation of space robots in the experiment/operation using real satellite. Therefore we have developed and used Audio Feedback System (AFS) that use some auditory information such as motorized sound and prerecorded voice converted from a part of telemetry information to reduce loads to operators of space robots of the Engineering Test Satellite VII(ETS-VII). We applied AFS to the experiment ofAntenna Assembling Mechanism (AAM) which is experiment module of the Communications Research Laboratory (CRL) on the ETS-Vil for testing the mechanism of assembling structures in space. Our purpose of this study is to assess effectiveness of AFS by using the Eye Mark Recorder (EMR) which records eye movements for the astronaut and two operators as telemetry monitor who observe telemetry data. In results of macro shape of 0-500 (deg/sec) velocity distribution graph, average fixation time, and average velocity of eye movement, we have got important points as followings: ( 1) the spectrum patterns of velocity of eye movement of specialist operator of controlling space robots like an astronaut are significantly differed from other two operators, (2) the spectrum patterns of velocity of eye movement of specialist operator and nonexpert operator are not affected ofAFS, (3) the spectrum patterns of velocity of eye movement of well-trained expert operator was similar to specialist operator with AFS and similar to nonexpert operators without AFS, (4) average fixation time of specialist operator was not effected by AFS, average fixation time of well-trained expert operator, nonexpert operator became long without AFS support.