zenichi yamamoto

A 2.1 GHz 200W GaN high power amplifier unit with a solid-state cooling equipment was fabricated in compact configuration. The four high power amplifier units were combined with a circular waveguide and the output power was obtained with 540W. In the high power amplifier unit, the two package-type GaN amplifiers are connected in parallel. The maximum power of 200W was realized with the Peltier device for heat sink. The high power amplifier unit shows the PAE of more than 50% with the AB-class operation under the temperature around 40 degrees. The combining efficiency of the combiner was achieved with about 80 %.

We introduce the Japanese large ground stations (UDS64m/USC34m) for deep space communications.

Selenological and Engineering Explorer is composed of a lunar orbiter 'Kaguya', and two small sub-satellites: Relay Satellite 'Okina' and VRAD Satellite 'Ouna'. It was launched in September 2007, and operated until June 2009. Ground stations for their operations were GN stations of JAXA, Usuda Deep Space Center (UDSC), and foreign stations. Among them, 64m antenna of UDSC executed the downlink of mission data from Kaguya, and the first experiments of 4-way Doppler measurements of lunar orbiter relayed by Okina. We report about the outline of these operations, and the new technology to achieve the 4-way relay link.

When a radio wave passes through the rocket exhaust plume, it is attenuated and Phase fluctuation occurs. The amount of attenuation caused by the rocket exhaust plume depends on frequency, motor pressure, atmospheric pressure and attitude of the rocket. We investigated the mechanism of signal attenuation theoretically from the flight data of M-V rocket, and estimated a radio wave model of the plume using electromagnetic field simulation. These results will be applicable to the designs of the rocket telemetry systems in the future.

資料番号: SA0200139000

M-V型ロケットのテレメータ/コマンドシステムは前世代のM-3SII型ロケットに比べて大幅に変更されている．M-V型ロケットもM-3SII型ロケットと同じく３段式であるが，M-V型では第3段に計器部が設けられ，その結果，そこにテレメータ送信機を搭載することとした．すなわち，第1段から第3段まで各段にテレメータ送信機を搭載することとした．第3段に搭載されるテレメータ送信機はS帯周波数を用い，伝送速度も高めた新規開発のものである．姿勢制御系データの伝送という重要な役割を担っている．搭載送信アンテナに関しては，ロケットの径が大きくなったことにより，M-3SII型の時のように単一のアンテナでは十分なカバレッジを確保できなくなったため，各段とも，2本のアンテナを，それぞれ180度離れた位置に取り付けた．地上局からのガイド送信により，KSC局，あるいは宮崎ダウンレンジ局にとって条件の良い方を選択した．地上送受信系については，M-3SII型の時とほぼ同様である．第2段燃焼ガスが通信回線に及ぼす影響を考慮し，宮崎にダウンレンジ局を設けた．受信結果はほぼ予想通りで，KSC局では第2段モータ点火と同時に，燃焼ガスの影響によりテレメトリデータに欠損を生じたが，宮崎ダウンレンジ局においてその間のデータ補完することができた．資料番号: SA0200138000

The New Precision Radar that the Institute of Space and Astronautical Science(ISAS) developed for the tracking of the scientific-satellite launcher and sounding rockets is described. The radar has been operating since 1996 at the Kagoshima Space Center(KSC)of ISAS, of which operations conducted include trackings of three M-V rockets and numbers of sounding rockets. The key features of the New Precision Radar are(1)a 7m diameter antenna and(2)complete digital processing of the signals at IF and the after-stages. The margin of the signal detection in the secondary radar mode(beacon mode)has been improved 10 decibels from that of the old Precision Radar which ISAS had been using for long years. In the primary radar mode(skin mode), the pulse compression with a compression ratio of 1000 has been achieved by digital techniques, and the maximum detection range has substantially been expanded.

This paper describes the satellite tracking station with a 34m diameter antenna that the Institute of Space and Astronautical Science (ISAS) has built at its Kagoshima Space Center for tracking of Earth-orbiting scientific satellites and deep space probes of ISAS. The features of the new tracking station are: a large antenna with high efficiency at S and X bands, reception of high bit-rate telemetry, polarization-diversity RF signal reception followed by a signal combiner, digitalreceivers, a new PN ranging system, an acquisition antennas system with transmit/receive capability, efficient station operation and satellite operatoin controls, and a Ka-band reception capability of the main antenna. Since the completion in 1998, the station has been operated for the tracking of the Mars explorer NOZOMI in support of the Usuda deep space station of ISAS and for the operations of the scientific satellites YOHKO, GEOTAIL, HALCA, and others.

The phase transfer to the space VLBI(Very Long Baseline Interferometry)satellite HALCA and the instrument system for it on board the spacecraft aredescribed. The phase transfer, supplying an extremely stable frequency-referencesignal to spacecraft by a radio wave from ground, is one of the key technologiesnecessary for space VLBI. The phase transfer for HALCA consists of such operations as:(1)a ground station transmits a 15.3 GHz up-link signal generated from a hydrogen maser frequency standard to the spacecraft,(2)a phase-lock receiver on the spacecraft receives the 15.3 GHz signal and generates the reference signal with a frequency of 50 MHz,(3)the reference signal is supplied to the radio astronomy instruments and the local signal generator,(4)the local signal generator generates a 14.2 GHz down-link carrier, together with local frequency signals for radio astronomy receivers,(5)the 14.2 GHz down-link carrier, which is QPSK modulated by radio astronomy signals, is transmitted toward ground, and(6)the down-link carrier is received and demodulated, and two-way loop phase is measured, at the ground station. The system on board the spacecraft has been confirmed, before the launch, to satisfy the coherence condition required from the VLBI correlation. The phase transfer has operated satisfactorily for the satellite HALCA in orbit and contributed to the success of the space VLBI observations by HALCA.

A new precision measurement radar for launching rockets has been developed in ISAS. The channel margin has been improved about 10dB comparing the existing system by using a larger antenna and implementing digital signal processing on the receiver. The maximum radar range at skin-tracking mode has been extended by long pulse transmission and pulse compression technique. The system has already been used for tracking of the M-V rockets and others and shown the expected performance. In this paper we report the system structure, the performance, and operational results of this radar.

In 1992, ITU allocated the 2-GHz band frequencies for the 3rd generation mobile radio communication system (IMT-2000) which can realize global service in the world. This system will beintroduced around 2001 in Japanafter the technical standard is regulated. It is very important to evaluate the characteristics of the interference with the Mobile satellite System (MSS) and existence satellite system when introducing IMT-2000 at 2-GHz band in the domestic marketBased on an official requisition from MPT (existing MPHPT (Ministry of Public Management, HomeAffairs, Posts and Telecommunications), the technical group which was organized by the Association of Radio Industries and Businesseshas investigated the interference between IMT-2000 and the 2 GHz band other service systems. This paper presents the result of the electric field strength data measurements on the interference effects between the 2GHz band communication systems. It shows the major interference models and the system of our experiments, and reports the filed performance between MSS system, Science satellite systems and DS-CDMA system on the 2 GHz band and the unmatched polarization propagation characteristics in thewideband system.

The phase transfer, supplying an extremely stable frequency-reference signal to spacecraft by a radio wave from ground, is one of the key technologies necessary for realizing space VLBI (Very Long Baseline Interferometry). This paper presents the phase transfer system for the scientific satellite HALCA (the name before the launch was MUSES-B) which was launched in 1997 by the Institute of Space and Astronautical Science (ISAS) and has become the first space VLBI satellite of the world. The phase transfer for HALCA is performed by using a two-way link, composed of a 15.3GHz ground-to-satellite link and a 14.2GHz satellite-to-ground one. A ground system for the phase transfer has been developed at the Usuda Deep Space Center of ISAS with such functions as: (1) Transmitting the up-link signal which frequency is Doppler-compensated such that the frequency becomes exactly 15.3GHz at the spacecraft, (2) receiving the downlink signal which has been transmitted from the spacecraft with the frequency of 14.2GHz keeping its phase coherent to the received up-link signal, and (3) detecting the loop phase and the two-way Doppler frequency shift from the received down-link signal. Great cares have been paid for achieving high phase stability in the design of the total system, each equippment and the circuits, of the ground station. A loop test at the Usuda station, using a satellite simulator, has shown that the ground system well satisfies the coherency requirement. For HALCA in the orbit, the phase transfer from the Usuda station has operated satisfactory, attaining phase stability necessary for the space VLBI observations under the VLBI Space Observatory Programme (VSOP).

The demands for drastic improvements in conventional communication systems are inevitable for more complicated deep space missions. We proposed regenerative pseudo-noise(PN)ranging scheme using synchronous integration of long period PN signals whose compatibility are excellent with equipments in our deep space stations. It was analyzed that its characteristics were not sacrificed in spite of its simplicity. The effectiveness in actually planned missions was also clarified in the example of MUSES-C mission. We demonstrated its performance by making breadboard model. The incorporation of regenerative ranging method in a transponder is now in process parallel to the development of next generation on-board X-band digital transponder, whose structure and specifications are also summarized.

A frequency and time standard system composed of three hydrogen masers has been operating at the Usuda Deep Space Center of the Institute of Space and Astronautical Science since 1998. A three hydrogen masers system is an ideal frequency standard for a deep space tracking station, since hydrogen masers can be operated with high reliability through relative phase comparisons among the masers. This paper describes the design and the operation of the three hydrogen masers frequency-and-time standard system that we have developed for the Usuda deep space tracking station.

Radio waves for communications between ground stations and rocket-powered vehicle are attenuated by rocket-exhaust plasmas. To investigate the attenuation characteristics and the physical mechanisms, the automatic gain control records at the ground stations during the M-V vehicle flight have been analyzed. Relations between the attenuation and look angle from the ground stations and multipath phenomenon that was observed are discussed. An combustion experiment using small-sized rocket motor to study the attenuation is briefly discribed.

The Institute of Space and Astronautical Science (ISAS) launched the scientific satellite HALCA on 12 February 1997 by the ISAS's M-V rocket. HALCA has become the first satellite of the world to challenge space VLBI.In the middle of May, about three months after the launch, fringes were first detected in the interferometry experiment with ground radio telescopes. In the middle of June, about four months after the launch, images of quasars were first generated by space VLBI.This paper describes the outline and the initial results of the space VLBI experiment of HALCA.

In February 1997, the Institute of Space and Astronautical Science, ISAS, successfully launched the first flight of the M-V rocket carrying the mission of space VLBI. The satellite injected into a highly elliptical orbit was named as the HALCA. The HALCA is equipped with an 8-m antenna and a VLBI data acquisition system but has no frequency standard on board. A Hydrogen maser frequency standard is indispensable to a WBI observation, so that a phase reference signal is generated in a Hydrogen maser oscillator in a ground tracking station and transmitted to the HALCA. In this paper propagation effect on the phase transfer is discussed and the stability of the path is reported.

In this report,we present two methods for estimating the solar wind speed with doppler frequency scintillation,which is calculated from the tracking signals of deep space probes.We have analyzed the solar wind speed in two cases;normal phase and under the influence of flare.In the analysis,we have used the range rate data of SAKIGAKE(TS-5)and SUISEI(PLANET-A),which were launched for probing Halley's comet in 1986.

Doppler frequencies of deep space probe tracking signalsfluctuate randomly when solar wind passes across ray-pathes of the radio waves. In this paper we present a method to extract Doppler scintillations from deep space probe tracking signals by applying filterings. We discuss the Doppler scintillations extracted from the tracking data of "SAKIGAKE" and "SUISEI".

This paper evaluates the performance of the Doppler measuring system at Usuda Deep Space Center. The system is used for the tracking of Japanese deep spacecraft "SAKIGAKE" and "SUISEI". It will be very important to evaluate the system performance since the tracking accuracies of the spacecraft are very sensitive to the Doppler frequency error. Here we evaluate the system performance by the analyses of the tracking data of "SAKIGAKE" and "SUISEI".

The US-Japan collaborative radio science experiment at the Voyager-Neptune encounter was successfully carried out on August 25,1989. The 64-meter tracking antenna at Usuda station, together with the NASA 70 meter antenna at Canberra and the Australian Parkes astronomical observatory, exibited their full capabilities and the structure of the Neptune atomosphere, its ionosphere, Triton's atmoshpere and ionosphere have been revealed for the first time.