We have developed a multi-mode integrated transponder with four schemes of modulation and conducted a demonstration test in orbit with a demonstration test model. We have also manufactured a qualification test model and completed development as a versatile component for JAXA satellites. The decision has been taken to include the MTP on board various JAXA satellites and it is currently in the manufacturing phase. We will subsequently report on the main functions of the MTP and the results of the demonstration test in orbit.
The Japan Aerospace Exploration Agency (JAXA) has developed an X–band Multi–mode High–speed Modulator (XMOD). Its first flight model will be installed on the Advanced Land Observing Satellite–2 (ALOS–2) scheduled for launch around 2013. The XMOD has 16–Quadrature Amplitude Modulation (16–QAM) and Quadrature Phase Shift Keying (QPSK) modulation schemes and achieves a transmission speed of 800 Megabits per second (Mbps) when 16–QAM is selected. This unit consists of fully internal redundant housing to achieve a light weight and compact design with minimum footprint. This paper describes an overview of XMOD design, key technologies, the test results of the Engineering Model (EM). Test results of the Single Event Effects (SEE) of XMOD’s baseband module to evaluate the radiation tolerance of the SRAM–based FPGA is also described.
Rechargeable cells, e.g. alkaline (Ni–Cd, Ni–MH, and so on) and Li–ion cells have important roles in spacecrafts. They store electric power from other power generation devices such as solar cells and supply it to all the components, especially during eclipses. Lithium–ion cells have many advantages such as high energy density, low self–discharge rate and no memory effect compared to conventional alkaline cells. The cycle life performance of large–scale lithium–ion cells has been evaluated by the Japan Aerospace Exploration Agency (JAXA) since the 1990s and the requirements for their use with spacecraft have been satisfied. Accordingly, large scale lithium–ion cells manufactured by GS Yuasa Technology Ltd. (GYT) were categorized by JAXA as key components and successfully approved for use in spacecraft. Recently, we have been studying the applicability of improved lithium–ion cells in spacecraft. We have accumulated a many kinds of data and are now ready for certification of lithium ion cell qualification for use in space.
To increase the ratio of mission payloads on spacecraft, compact and lightweight electrical power subsystem (EPS) is demanded. Previously, since the EPS of our program was not in line with the trends, mass ratio and handling power, of the global market, a new EPS was developed to halve the ratio of mass and handling power in line with global requirements. This paper presents the new technologies adopted to achieve weight reduction, introduce ideas and developments in power control units and power distribution control unit.
In 1980, the first generation Japanese 1N thruster was developed by JAXA (NASDA at the time) and IHI Aerospace (IHI at the time), the design of which was based on the US TRW 1970s design. More than 180 thrusters have been loaded on the NASDA–JAXA satellites for over 25 years. But the satellite mass and life time have been extended since then, therefore the old 1N thruster didn’t satisfy the life requirement of Japanese satellites mission completely. After extensive basic research, the development program of new 1N thruster started in 2009. We tried to overcome the disadvantages of the old 1N thruster and fundamentally change the design. In the development of the new long life 1N thruster, the qualification test program was successfully completed. In the QT firing tests, over 200,000Nsec and 850,000 pulses (it means over 100kg throughput of hydrazine) were achieved and the long life of the thruster was demonstrated. Also in the ΔQT firing tests, the relationship between the thruster life and its firing mode were unveiled by eleven PM thrusters. The new long life 1N thruster is now ready to deliver.
Mechanical cryocooler for space application is efficient way to cool down the optical detector, telescope and thermal shields to cryogenic temperature below about 100 K in the aspect of mass and size. The 20 K-class double-stage Stirling cycle cryocooler with cooling power of 200 mW at 20 K and lifetime of 1.5 years was originally developed for a cooling component of the Japanese IR telescope satellite AKARI launched in 2006. Based on this AKARI cryocooler, improvements with higher cooling performance and reliability with 1) the optimized 8-mm diameter displacer at second stage, 2) the flexure bearings for displacer supporting and 3) selection of low-outgassing materials and optimal baking process were investigated to develop the second-generation double-stage Stirling cryocooler for application to the next innovative astronomy mission such as ASTRO-H/SXS (2015) and SPICA (2022). The verification tests by using the EM (Engineering Model) were performed and maximum cooling power of 17.6 K with 200 mW at the 2nd cold stage and 96.1 K with 1000 mW at the 1st cold stage was obtained with margin. Mechanical performance test was also carried out and proved tolerability for mechanical environment of qualification level of ASTRO-H⁄SXS. Continuous running to verify specified lifetime of over 3 years is still under testing and 13545 hours (~ 560 days) in total has just achieved as of August 2012.
Recently, scientific satellites and earth observation satellites have required more accurate pointing and higher angular rate maneuver capabilities. Autonomous attitude determination without a priori information has also became important, reflecting the need to simplify satellite systems and operations. To realize these requirements, we have been developing a precision autonomous star tracker for agile spacecraft, which is named the Next-Generation Star Tracker (NSTT). NSTT provides high-accuracy attitude determination results: random error is less than 4 arc seconds (3σ), while bias error is respectively less than 6 and 4 arc seconds (3σ) for wide and narrow temperature range. NSTT is able to track and acquire stars under high attitude-rate of 2 deg/s with 99.9% probability. A qualification model of NSTT has been manufactured and its functions and performances have been evaluated by qualification tests. NSTT is planned to be installed on the next X-ray observation satellite, ASTRO-H. This paper describes the technical challenges of NSTT and our solutions for them. This paper also presents the system design, manufacturing results and some test results of NSTT.
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