The COMETS satellite

A concept for a future advanced mobile satellite communications system using a geostationary satellite is described. In the satellite of this system, a multiple spotbeam antenna, onboard beam interconnection, and millimeter-wave and Ka-band components are required. The configuration of the payloads of Japan's COMETS (Communications and Broadcasting Engineering Test Satellite) for advanced mobile satellite communication experiments is also described. The transponder has an IF filter bank and a SCPC/TDM (signal-carrier-per-channel/time-dimension multiplexing) regenerative modem for beam interconnection. >

Mission Profile of Advanced Satellite Broadcasting System on Communications and Broadcasting Engineering Test Satellite (COMETS)

Although wide industrial use of liquid hydrogen is anticipated in the future, its present application in Japan is almost entirely limited to the space program. The combination of liquid oxygen and liquid hydrogen (LOX/LH2) gives the highest performance among the propellants now used for space launch vehicles. LOX/LH2 engines were used for the huge rocket, Saturn, which sent astronauts to the moon, and are to be used for the first reusable launch vehicle, Space Shuttle of the United States.A program to develop a LOX/LH2 engine is being carried out also in Japan by the National Space Development Agency of Japan (NASDA). The engine which develops 10ton thrust in vacuum is to be used as the second stage of the future Japanese launch vehicle, H-I.The final configuration and the development plan of the H-I launch vehicle is now being discussed, and might be settled before the end of FY 1979. For the time being, develoment efforts will be concentrated on the second stage with a LOX/LH2 engine and inertial guidance system.A combination of the newly developed second stage and the first stage of the N-II launch vehicle, which is an improved version of the present N-I, is called Test Vehicle (tentative) and will be developed as a first step of the H-I program. The main objective of the first flight of the Test Vehicle, which is scheduled for late FY 1984, is to verify the integrity of the second stage. The Test Vehicle is a two stage vehicle and can launch a satellite into low earth orbit. If a third stage is added, it can place a payload of more than 500kg into geostationary orbit.The second stage is the core of the Test Vehicle. It consists of a LOX/LH2 engine, tank, inertial guidance system, control system, and others. The LOX/LH2 engine is the key element to improve the capability of the launch vehicle.NASDA has conducted the development tests of the major components of the engine since FY 1975, in cooperation with the National Aerospace Laboratory (NAL) and the Institute of Space and Aeronautical Science (ISAS) of the University of Tokyo. When the tests were initiated, use of liquid hydrogen in Japan was very limited. NASDA had to start from basic tests using liquid hydrogen produced by a small pilot plant. A large commercial plant was constructed in FY 1978, and now tests of full scale components are conducted on regular schedule.Topics covered in this paper are;(i) LOX/LH2 engineFollowing a brief description of rocket engine fundamentals, characteristics of liquid hydrogen as a rocket propellant will be stated. LOX/LH2 engines developed and being developed in the United States and European countries will be shown as examples.(ii) Development of a LOX/LH2 engine in JapanAn outine of the H-I program will be described. Main characteristics and development tests of the second stage will be stated, laying stress on the LOX/LH2 engine.

Global Change Observation Mission (GCOM) is a follow on mission of ADEOS, ADEOS2 and TRMM. It is under phase A study in NASDA (National Space Development Agency of Japan). GCOM is not a series of satellites but a mission and its concept is to continuously monitor geophysical parameters which are critical to understand global change phenomena, especially phenomena related to climate change. Those parameters include, but not limited to, optical thickness of aerosols and clouds, water and energy fluxes, carbon fluxes, sink and source of greenhouse gases, atmospheric constituents, etc. The measurements of geophysical parameters will continue more than 15 years after the launch of ADEOS2 is now composed of 3 satellites, i.e. GOSAT (joint program of NASDA and MOE), CCOM(tentative name), and CPM core satellite (joint program of NASDA and NASA). The main target of GOSAT is to clarify the sinks and sources of greenhouse gases, especially carbon dioxide, in the continental scales by monitoring atmospheric greenhouse gases distribution. The target of CCOM is to measure geophysical parameters which are uncertain in the today’s climate models. GPM core satellite is a follow on TRMM and the target of GPM core satellite is to measure precipitation. GOSAT will carry at least 2 instruments, i.e. an instrument which can measure tropospheric carbon dioxide, and SWIFT (Stratospheric Wind Interferometer : stratospheric wind sensor). CCOM will carry three core instruments, i.e. SGLI (GLI follow on, which covers from UV to IR), AMSR2 (AMSR follow on), alpha-Scat (SeaWinds follow on). Other instruments may be added based on an AO process. GPM core satellite will carry 2 instruments, i.e. DPR (Dual Precipitation Radar : PR follow on) and a microwave radiometer. The orbit of CCOM will be a sun synchronous orbit, which is almost the same as ADEOS2. The orbits of GOSAT and GPM core satellite will be around 70 degree inclination orbit and the altitudes will be 700km and 400km, respectively. These 3 satellites are planned to be launched in 2007 and 2008. While GCOM mission is focused to global change, NASDA has other satellite series, starting from MOS-1 to JERS-1. The next satellite to follow the JERS-1 is ALOS (Advanced Land Observing Satellite), which will be launched in 2004. The mission of ALOS is to provide sufficient data, which enable to generate 1 to 25,000 scale base maps all over the world.

Optical free-space communications is a promising technology for future space activities. National Space Development Agency of Japan (NASDA) began developing the Optical Inter-orbit Communications Engineering Test Satellite (OICETS). OICETS carries an optical communications equipment named Laser Utilizing Communications Equipment (LUCE) and will be launched in 1998. NASDA plans to conduct an inter-orbit optical communications experiment which will be performed under the international collaboration between NASDA and European Space Agency (ESA). Communications system of LUCE employs the IMDD technique which uses LD as a transmission device and APD as a detection device. The preliminary design of OICETS including LUCE has been completed. The paper describes the result of design and planned experiments for optical communications system of OICETS.

In Japan, there are two main launch vehicle development activities. One is the development of the M launch vehicle series, a solid propellant rocket, by the Institute of Space and Astronautical Science for scientific missions. The other is a development program of large-size liquid propellant launch vehicles for practical satellite launch by the National Space Development Agency of Japan. Until now, two activities are making progress on their respective courses, and Japanese space programs have achieved the level of Western countries. In this document, the development of the H-II launch vehicle by the National Space Development Agency of Japan (NASDA) is mainly discussed.

Researches on reusable launch vehicle (RLV) in Japan have been conducted mainly by the three space agencies: the National Space Development Agency of Japan (NASDA), the National Aerospace Laboratory of Japan (NAL) and the Institute of Space and Astronautical Science (ISAS). HOPE‐X program by NASDA/NAL, spaceplane/scramjet related researches by NAL, and development studies of ATREX engine and small reusable vehicle testing (RVT) by ISAS are such major activities. After the consecutive launch failures of NASDA’s H‐II and ISAS’s M‐V rockets in 1999–2000, it was concluded that more intensive efforts should be concentrated on the reliability improvement of those major expendable vehicles and that RLV related researches should be promoted to establish fundamental technologies essential to future RLV. In past two years, NASDA succeeded in five consecutive launches of new H‐IIA, and ISAS successfully resumed the launch of M‐V. As for RLV researches, considerable progress has been achieved in the high speed flight demonstration (HSFD) tests of HOPE‐X program, scramjet tests of Mach 4 to 8 by NAL, and ATREX engine and small RVT tests by ISAS. The current three space agencies will be merged into one in October 2003 to establish a new organization named Japan Aerospace Exploration Agency (JAXA). It is expected that the above research activities will be also merged to promote a higher‐level research program on RLV.

The technological advances of the space age owe much to the political and military pressures of the Cold War between the US and Soviet Union. The recent collapse of the Soviet Union, and the ending of the Cold War, however, have made it increasingly difficult for countries to justify continued investments solely on the basis of political prestige or scientific advances; in today’s environment, space activities must also be perceived as a wise economic investment.The National Space Development Agency of Japan (NASDA) believes that the future success of the public sector space efforts will depend icon objectives which go beyond technological advancement for its own sake; rather, future efforts should provide tangible social and economic benefits that can be readily identified and appreciated by the society which provides the funding for them. The key to realizing such goals is a flexible, adaptable and inexpensive space infrastructure (the foundation upon which all other activities are built), an infrastructure which is viewed as a means of stimulating the utilization of space, rather than an end in its own right.Based on these understandings, NASDA has been conducting studies for several years on an innovative space infrastructure. This paper analyzes the impact which an innovative space infrastructure could have, not only on the Communication/Broadcast Satellite markets which exist today, but also upon the potential new markets which would emerge. The paper assesses potential market character and size using an original quantitative prediction model. Furthermore, this paper examines the development of future scenarios for exploitation of lunar resources and solar energy, as well as attempts to verify the actual effectiveness of the proposed fully reusable space infrastructure.

A High-Speed Flight Demonstration (HSFD) project is the latest in a series of flight experiments in a joint research program into reusable space transportation systems being conducted by the National Aerospace Laboratory of Japan (NAL) and the National Space Development Agency of Japan (NASDA) (NAL and NASDA were merged to form Japan Aerospace Exploration Agency-JAXA on October 1, 2003). The project consists of two phases: Phases I and II. The objective of Phase I is to verify approach and landing systems for the final part of the return phase of a winged re-entry vehicle. The Phase I flight experiment was conducted in Christmas Island in Republic of Kiribati, from October to December 2002. Through three flights, the approach and landing system was evaluated during steep gliding, which is characteristic of return flights of winged reentry vehicles, and autonomous flight technologies essential for future space transportation systems were accumulated. The purpose of the Phase II is to clarify the transonic aerodynamic characteristics of the demonstrator, and data obtained from wind tunnel tests and Computational Fluid Dynamics (CFD) are evaluated against the flight test data. A Flight experiment of Phase II was conducted at Esrange test site in Sweden from May to July 2003 in collaboration with Centre National d'Etudes Spatiales of France (CNES) which developed and operated the balloon system. Although the flight experiment was interrupted due to the anomaly of the recovery system, various data at Mach 0.8 were obtained through the flight, and fully autonomous flight control technologies for transonic speed region were demonstrated. The data obtained from the HSFD project are expected to provide essential information for development of future reusable space transportation systems.

The National Space Development Agency of Japan (NASDA) is currently developing a new spaceborne lidar system, the so-called Mission Demonstration lidar (MDS-lidar) or Experiment Lidar In Space Equipment (ELISE). The system will be launched in the early 2000's. Its goals are to demonstrate the applicability of some key components for the long-term operation of a lidar in space and to provide scientific data from one year observations for climatological studies. At present a simulation study is conducted to estimate ELISE's performance for observations of clouds and aerosols. Due to the global measurement coverage a broad range of atmospheric conditions has to be considered. We will present simulation results regarding system calibration and quantitative measurements with ELISE.

Soil Moisture Active Passive (SMAP) is a NASA-developed Earth science satellite currently mapping the soil moisture content and freeze/thaw state of Earth's land mass from a 685km, near-polar, sun-synchronous orbit. It was launched on January 31, 2015 from Vandenberg AFB upon a Delta II 7320 launch vehicle. Due to external considerations, SMAP's launch vehicle selection remained an open item until Project Critical Design Review (CDR). Thus, certain key aspects of the spacecraft design had to accommodate a diverse range of candidate launch vehicle environments, performance envelopes, interfaces and operational scenarios. Engineering challenges stemmed from two distinct scenarios: decisions that had to be made prior to launch vehicle selection to accommodate all possible outcomes, and post-selection changes constrained by schedule and the existing spacecraft configuration. The effects of the timing of launch vehicle selection reached virtually every aspect of the Observatory's design and development. Physical environments, mass allocations, material selections, propulsion system performance, dynamic response, launch phase and mission planning, overall size and configuration, and of course all interfaces to the launch vehicle were heavily dependent on this outcome. This paper will discuss the resolution of these technical challenges.

The H-ll Rocket has been developed by National Space Development Agency of Japan(NASDA). to meet demands of heavy lift launchers for various applications in 1990s. The maiden flight of H-ll Rocket was conducted on February 4th,1994 successfully. H-ll Rocket should be work-horse rockets for Japan's near term future space activities. But there are some scope for the improvement of its reliability and cost. Several studies for improving further cost reduction and enhancing launching capability and reliability are under considerations, as upgraded H-ll Rocket and H-ll Rocket for HOPE-X (HOPE experimental plane which will be launched on top of H-11). In these configurations, LE-7 Engine is the key component of its propulsion system. Improved LE-7 Engine will be applied to near term future launch vehicles, as H-ll Rocket for HOPE-X and Upgraded H-11. Improved LE-7 Engine, as new Japanese expendable booster engine, is starting to develop. This paper presents the current status and future improvement plan for Improved LE-7 engine. J

NAVIGATION AND GUIDANCE OF THE H-11 ORBITING PLANE

A new airborne multi-frequency Synthetic Aperture Radar (SAR) was developed by the Communications Research Laboratory (CRL) and National Space Development Agency of Japan (NASDA). This system observes the Earth's surface by multi-frequency (L- and X-band), all polarization and high resolution radar. Furthermore the system has a topographic mapping function for X-band by a crosstrack interferometric SAR. In this report the authors describe their SAR system and preliminary results of the test flights.

The authors carried out calibration experiments of the C-band synthetic aperture radar (SAR) of the first European Remote-Sensing Satellite (ERS-1) with its three passes over Japan in June, July, and August 1993, employing an active radar calibrator (ARC) and a corner reflector (CR) both located in the site of Kashima Space Research Center (140/spl deg/40'E, 35/spl deg/57'N) of the Communications Research Laboratory. The ARC has a large radar cross section (RCS) of over 60 dBm/sup 2/, with a function to shift the frequency of signals when retransmits that makes the position of the ARC shift in the SAR image. Frequency shifts of the ARC were set to 0, 200, 400 Hz for the three passes each, so that the ARC echo should appear at 0, 640, 1280 m shifted in the azimuth direction from its actual location in each SAR image. Received power by the ARC was recorded during the overpasses, which shows an antenna pattern of the SAR. The authors also used a corner reflector of 1.1 m square trihedral (RCS=42.4 dBm/sup 2/) as a landmark, as well as another calibration target. Obtained SAR image data processed by National Space Development Agency of Japan (NASDA), the authors have examined image amplitude (data numbers) and locations of both of the ARC and the CR. It is seen in the SAR images, as expected, that the positions of the ARC are shifted depending on the shift of frequency. >