Communications And Broadcasting Engineering Test Satellite Research Articles

Ka-band aeronautical satellite communications experiments using COMETS

This paper describes the results of evaluation tests of an aeronautical satellite communications experiments system in the Ka-band using Japan's communications and broadcasting engineering test satellite (COMETS). An active phased-array antenna with an open-loop satellite tracking capability operating in the Ka-band was installed just behind the passenger window of an airplane to receive a satellite signal. The propagation measurements showed that the received signal power was stable within a signal-power variation of 1 dBp-p while the airplane was cruising at 600 km/h. At specific directions of the antenna, the radiowave reflected from the wing of the airplane was measured to be 18.5 dB lower in power compared with the line-of-sight signal. To confirm the designed link budget, the multibeam antenna pattern of COMETS' on-board antenna was measured while the airplane flew across two antenna beams. The antenna pattern matched the one measured in a ground test before launch. Two binary phase-shift keying (BPSK) modems, one for pilot-assisted coherent detection and the other for multiple-symbol differential detection, were used to measure the bit-error rate (BER). The measured received signal energy per bit per noise power density (E/sub b//N/sub 0/) at a BER of 10/sup -4/ showed only a small degradation of about 1 dB from that measured in a translator loop-back test.

COMETS experiments for advanced mobile satellite communications and advanced satellite broadcasting

The Communications and Broadcasting Engineering Test Satellite (COMETS) was developed to evaluate Ka-band (31/21GHz) and millimetre-wave (47/44 GHz) advanced mobile satellite communications systems, 21GHz advanced satellite broadcasting systems, and S-band and Ka-band inter-orbit satellite communications systems. COMETS was launched because it was to become the new ‘bridge’ toward advanced satellite communications technologies in the next century, but the launch on 21 February 1998 regretfully failed due to premature shut down of the second stage engine of the H-II launch rocket. After this accident, the initial low elliptic orbit of COMETS was improved by the apogee engine to a larger elliptic orbit with an apogee altitude of 17711km, a perigee altitude of 473 km, an inclination of 30.1°, and an orbital period of 319 min. Original and modified COMETS experimental plans, countermeasures in earth stations for the orbiting satellite, as well as an overview of the COMETS satellite and ground terminals are presented. Copyright © 2000 John Wiley & Sons, Ltd.

Cooperation Control Experiment of Communications and Broadcasting Engineering Test Satellite(COMETS).

Communications and Broadcasting Engineering Test Satellite(COMETS)which was launched on February 21 in 1998 has a large movable antenna. This paper deals with a method to compensate disturbances caused by the antenna motion to the spacecraft attitude. The disturbances are calculated and compensated on-orbit based on the predicted antenna parameters. Then the parameters are estimated and modified from the results of the on-orbit compensation. The on-orbit experimental results show that the disturbance compensation is effective to reduce the spacecraft attitude error and becomes better by using the modified disturbance parameters.

Real-time trajectory estimation experiments with the COMETS spacecraft

NASDA has developed a new trajectory estimation program capable of estimation in real-time. NASDA conducted experiments to verify the performance of the program with Engineering Test Satellite VI(ETS-VI) in 1994, as well as with Communications and Broadcasting Engineering Test satellite (COMETS), in March and May 1998. This paper presents an overview of the real-time trajectory estimation experiments with COMETS.

Experimental advanced mobile satellite communications system in the mm‐wave and ka‐band using communications and broadcasting engineering test satellite

AbstractIt is expected that the demand for personal satellite communications will increase and systems providing various services enabling direct communications between automobiles and portable stations will be in demand in the near future. Load transponders and experimental systems are being developed and studied for the advanced mobile satellite communications systems of the Communications and Broadcasting Engineering Test Satellite (COMETS) expected to be launched in 1997 in order to develop and verify multibeam interconnection technologies and regenerative repeater technologies as technologies required to implement such next‐generational mobile satellite communications systems.In this paper, the functions required by COMETS experimental systems have first been clarified, assuming future systems. Next, the payload configuration satisfying the required functions and performance has been designed based on the conditions restricting the load. As a result, a batch‐type regenerator using a digital polyphase‐fast Fourier transform (FFT) filter bank, Ka‐band 20‐W solid‐state power amplifier, and a millimeter‐wave low‐noise amplifier (N.F. = 2.4 dB) has been realized. In addition, experiments have been considered employing the experimental system using the foregoing.

The Attitude Control Subsystem and Inter Orbit Pointing Subsystem for Communications and Broadcasting Engineering Test Satellite

This paper shows the design of Attitude Control Subsystem (ACS) and Inter Orbit Link Antenna Pointing Subsystem (IOL-APS) for Communications and Broadcasting Engineering Test Satellite (COMETS). At first, we show the design of each subsystem. Next, we explain about the cooperative control. Last, we show the test to verify the performance of ACS and IOL-APS.