戸田 知朗

SCOPE is the magnetospheric explorer mission using a distributed sensing system to investigate space-time correlation of particle behaviors in the magnetotail. The mission needs an autonomous inter-satellite link system enabling commanding, data transfer, ranging, and timing control support for data sampling in unison in a distributed system. TDM/TDMA system has been proposed so as to fit to SCOPE specification. We have developed a simulator to validate our design for SCOPE and obtained successful results. As an instrument to work within a limited resources of small sized satellites like SCOPE, data link, ranging performance, timing accuracy satisfy requirements of SCOPE mission. We describe our inter-satellite link system and achievements obtained through the simulator experiments.

JAXA is currently planning the next generation magnetosphere observation mission called "SCOPE"(cross-Scale Coupling in Plasma universE). SCOPE aims at observing the Earth's magnetotail with 5 satellites flying in formation to fully resolve the temporary and spatial distribution of the magnetospheric phenomena. For this observation, the clock synchronization and relative distance measurement between the spacecrafts are essential. This paper describes an onboard relative ranging and clock synchronization algorithm, which applies a simplified formulation, using two-way and three-way phase differences as the filter inputs to construct the onboard system suit to the SCOPE mission.

SCOPE (cross Scale COupling in the Plasma universE) is a project designed as a successor of GEOTAIL and AKEBONO launched by ISAS/JAXA in 1992 and 1989 respectively. The scale coupling phenomenon in the Earth magnetotail has attracted many attentions after the work of the two precedent missions. SCOPE explores the vast area of magnetotail with a method of simultaneous multi-point probing by formation flying satellites to reveal complex behaviors brought by electrons, ions, and electromagnetic field in it. This mission demands satellites to be more interconnected via communication links than ever to approach to time-and-space resolved new facts in the magnetotail. In this paper, the outline of the communication system designed for JAXA's first formation flying mission: SCOPE will be presented. The key issues are the resource-limited developments for small satellites and the construction of an efficient wireless interlink enabling highly resolved correlation measurements in time-and-space.

The planetary exploration activity in ISAS was initiated by NOZOMI, Mars atmospheric surveyer launched in 1998. Based on the experience gained through this project, new planetary exploration programs have been investigated to lead our deep space activities in the 21stcentury. The Venus Climate Orbiter and Mercury Magnetosphere Orbiter are our missions selected for the first decade of the 21stcentury. In response to this decision, the review on communication capabilities of ISAS has been conducted from the viewpoint of reliability and cost-performance. The development of a new X-band transponder, research-oriented ground system, and turbo decoder test-bed was considered the most effective to support the missions. The X-band transponder is for the optimized and established onboard communication equipment meeting various demands of scientific missions in ISAS. The ground system directly works as a test-base of new communication technologies adopted in the new transponder and also serves as a demonstrator enabling prompt applications of laboratory technologies to missions in the future. The turbo coding scheme will be included in this ground system. The turbo decoder is under development so that its implementation in our ground station will be in time for the Mercury mission. In the following, we will discuss these developments and detailed configurations.

光衛星間通信のような点対点の通信で用いられる光アンテナは,高開口能率である必要がある.鏡面修整法を用いることにより,高開口能率,低サイドローブであるアンテナを設計することができるが,鏡面が高次の多項式を含む非球面となり,製作過程の誤差に対し極めて弱くなる.本研究では修整面が高次の多項式を含まないような修整光アンテナを提案し,誤差特性の改善をめざす.開口能率と独立なアンテナパラメータを変化させ,最も低次の非球面で構成できる修整光アンテナを設計し,従来の鏡面修整光アンテナと誤差特性の点で比較を行う,その結果,提案する修整光アンテナは従来の修整アンテナと比べて製作が容易になるだけではなく,非修整アンテナとほぼ同じ誤差耐性を有することを示す.

鏡面修整アンテナは鏡面形状が特殊になり、光の波長が非常に短いため、製作誤差に対し極めて弱くなる。本報告では修整面を給電部と副鏡とすることで、誤差に対する依存性が少ない光学系を提案する。各種誤差に対して最適になるように設計パラメータを算出し、標準カセグレンアンテナ、従来の鏡面修整アンテナと本報告で提案するアンテナとの製作誤差特性を比較した。その結果、従来の鏡面修整アンテナより誤差特性が改善し、標準カセグレンアンテナとほぼ同じ製作許容誤差となった。これは修整曲面形状が非常に単純となり、要求加工精度も現実的になることによる。

Mass transport method has been developed as a high quality quantum wire (QWR) array formation technique in InP systems. It was demonstrated that strained InAsP QWRs with the lateral width less than 20 nm could be formed at the sharp bottom edge of InP V-grooves without any parasitic structures. Their emission peak wavelength and size were controllable by temperature and group V ambient pressure ratio. A distributed feedback (DFB) laser was fabricated by utilizing the mass-transported strained InAsP QWR array on GainAsP V-grooved substrates as an active grating. Lasing at 1.53 μm at 20 °C by pulsed current injection was accomplished. Record low threshold current density of 0.112 kA/cm2 was obtained in a broad area laser with a 100 μm-wide and 750 μm-long cavity.

MOVPEに基づくマストランスポート法を用いInP基板V溝上にInAsP量子細線を作製することに成功した。量子細線のサイズはマストランスポートを行う温度によって制御可能であり、それとは独立に歪み及び細線の組成はマストランスポート中のV族雰囲気の組成で制御可能である。作製された量子細線はバリアとの強い格子不整合にも関わらず転移はの全くない良好な界面を有し、従来のV溝による作製法とは異なり余計な寄生構造を持たない特長をもつ。PLは室温においても強い発光を観測し量子細線の品質を裏付けている。また量子細線に固有の発光強度の偏波依存性も見られTEMによる観測と合わせてキャリアの有効な閉じ込めが推察できた。