Engineering Test Satellite VIII Research Articles

3402 技術試験衛星VIII型による軌道上システム同定実験計画(S87-1 飛翔体のモデリングとシステム同定(1),S87 飛翔体のモデリングとシステム同定)

This paper studies on-orbit system idntification experiment on Engineering Test Satellite-VIII (ETS-VIII), which will be launched in 2006 by H-IIA type 204 rocket. This will become the largest three-axis stabilized geoshncronous satellite in Japan. In the experiment, flexible parameters of large deployable antenna and large solar panels will be estimated by the downlinked telemetry data of stellite attitude and solar panel mounted accelerometers during the satellite check-out phase. We developed "ACFS Tool" for estimating onboard satellite attitude states using dwell data in the telemetry. In this paper, we show the the validity of the tool by numerical simulation.

Sustained arcing studies on the 110 V solar arrays in the ion thruster plasma and geosynchronous orbit environments

The sustained arcing mechanism in the solar arrays of Engineering Test Satellite-VIII (ETS-VIII) due to the failure of the ion thruster neutralizer and due to the development of inverted potential gradient on the solar arrays in the geosynchronous earth orbit (GEO) is presented. Failure of the ion thruster neutralizer is simulated in a laboratory, and the sustained arc is observed at the gap between the adjacent cells of the solar array without room temperature vulcanization silicon grouting with a potential difference of 55 V and a current of 2.64 A. The grouting prevents a sustained arc even under the worst condition expected for the satellite. The sustained arc is observed bridging two interconnectors separated by 6 cm with an inter-string voltage of 130 V and a current of 2.64 A for the array with RTV grouting. In a simulated GEO environment, it is confirmed that the sustained arc does not occur between the adjacent array strings as long as silicon rubber grouts the gap between the strings. We observed another type of sustained arc between the array strings and the aluminum honeycomb substrate through defect on the Kapton sheet in a simulated GEO environment. Based on the test results, modification of the array design is possible.

Simple satellite-tracking stacked patch array antenna for mobile communications experiments aiming at ETS-VIII applications

The Japan Aerospace Exploration Agency (JAXA) plans to launch a geostationary satellite called Engineering Test Satellite-VIII (ETS-VIII) in 2004. In the paper, the feasibility of reaching a relatively high value of gain at low elevation angle by use of a simple left-handed circularly polarised four-element stacked patch array antenna for mobile satellite communications in the S-band frequency aiming at ETS-VIII applications is discussed. The characteristics of this antenna are confirmed by two numerical methods (the method of moments and the finite element method) and by measurements. Furthermore, the influence of the finite size of the ground plane was analysed using of the finite element method. Both numerical analyses and measurements are presented. In addition, the operation of beam-switching is experimentally confirmed. It is revealed that, by properly feeding the patches constituting the antenna, for an elevation El=48° (θ=42°) in Tokyo, four beams are created in the conical-cut direction at azimuth Az=6°, 96°, 190°, and 276°. The gain reached more than 6.5 dBic on the whole azimuthal range, with an axial ratio less than 3 dB.

F212 技術試験衛星VIII型(ETS-VIII)搭載展開型ラジエータの開発(オーガナイズドセッション22 : 熱輸送デバイス)

High-powered satellites are required to obtain more heat rejection area. Deployable radiator, which is stowed during launch and deployed in orbit to obtain the additional heat rejection area, is key bus technology. This paper presents a design and engineering model test of developed deployable radiator on ETS-VIII (Engineering Test Satellite VIII) using RELHP (Reservoir Embedded Loop Heat Pipe). RELHP has an evaporator, condenser and transport lines to circulate a fluid, and that utilizes the evaporation and condensation of the working fluid to transfer heat. Developed RELHP has following characteristics. (1) It has 1.0 micron pore diameter fine-poured wick to achieve more higher heat transport capability. (2) It can start-up at any time by supplying the wick with working fluid, because liquid reservoir is located in the evaporator itself. Results of the thermal balance test and analysis will be described and discussed.

221 技術試験衛星VIII型による軌道上柔構造パラメタ同定実験 : 実験概要とケーススタディ(宇宙構造物・飛翔体の制御I)(OS 宇宙構造物・飛翔体の制御)

The Engineering Test Satellite VIII(ETS-VIII), which will be launched in 2003, has large flexible appendages such as deployable antennas and paddles. On the other hand, high attitude accuracy is required, but it is hard to determine its flexibility parameters correctly under 1G circumstances of ground test facilities. The on-orbit system identification of its dynamics is very beneficial for this case, because it enables the validation of flexibility parameters used in the design phase, and besides the controllers gain tuning. The experiment of this identification is planed now. In this paper, we explain the overview of this experiment system and summarize the results of preliminary case studies for the system identification of the ETS-VIII dynamics model. In the case studies, it is assumed to use 1) attitude and translational responses during longitude station keeping maneuver, 2) step responses in normal operation mode and 3) impulse response in normal operation mode. The identification is feasible if the impulse responses are available. The responses during station keeping maneuver are not efficient for this identification without changing the conditions (e.g. the firing pattern of station keeping thrusters).

Technology status of the 13 m aperture deployment antenna reflectors for engineering test satellite VIII

Large deployable antenna reflectors for Engineering Test Satellite VIII (ETS-VIII) are now stated in the critical design phase. The Fourteen 4.8m modules, which construct a 19.2 m × 16.7 m (13m aperture) antenna reflector, have been fabricated as Engineering Models. Ground testing for the fourteen modules will be performed until next spring. This paper describes results of critical design for the antenna reflectors and their validation plans. Each module consists of a gold-plated molybdenum mesh surface, spacially determined cable network, and a deployable truss structure as a supporting structure. Stowed size is 1 m (diameter) × 4 m (height). In stowed configuration, the lowest eigen frequencies of the antenna reflector are 47 Hz (longitudinal) and 69 Hz (lateral) respectively. The lowest eigen frequency is 0.14 Hz. Solar ray transparency of the reflector structure is designed to be more than 85% to avoid excessive solar pressure torque. Weight of each reflector is expected to be less than 100 kg. In addition, we will perform a piggyback deployment experiment in transfer orbit using the second stage of the first flight H-II A vehicle in 2000. Half scale seven modules antenna reflector will be used to validate its deployment reliability. Design, analysis and test results of LDR-P are also introduced in this paper.

Comparative study of switching methods for the on-board processor in a mobile satellite communications system

An on-board processor makes efficient use of the channel capacities in a satellite communications system employing multibeam technology, and an on-board processor has been developed for the Engineering Test Satellite VIII (ETS-VIII), which is the experimental satellite for a multibeam mobile satellite communications system. The multicarrier time division multiple access (MC-TDMA) system used in this communications system, however, sometimes causes internal congestion in the on-board processor. This paper describes the results of computer simulation studies of the traffic capacity obtained using three baseband switching methods and also describes the results of studies of the on-board processor design for each of the methods. The computer simulation results indicate that the probability of internal congestion due to the TDMA system is very small when the simultaneous-slot switching method is used, and the design study results reveal that an on-board processor using the simultaneous-slot switching method will be compact and lightweight and will consume little power. © 1998 John Wiley & Sons, Ltd.