Site: The Institute of Space and Astronautical Science (ISAS)
Sagamihara, Kanagawa 229, Japan
Date Visited: June 5, 1997
WTEC: S. Townes (report author), J. Pelton, A. Mac Rae, W. Brandon, C. Bostian
The Institute of Space and Astronautical Science (ISAS) is a national institute for space and astronautical science research. It is a part of the Ministry of Education, Science, Sports and Culture. As such, it has close ties to Japanese universities, particularly the University of Tokyo, which was its birthplace, and plays a role in promoting university-based activities and on-site graduate education. In addition to fundamental research and applied research in space science and technology, ISAS is a project-oriented organization with a long history of launch vehicles and scientific spacecraft. The 1997 budget for ISAS was 21.41 billion yen.
Organizationally, there are nine research divisions within ISAS. These are Space Astrophysics, Space Plasma, Planetary Science, Basic Space Science, Space Systems Engineering, Space Transportation, Space Propulsion, Spacecraft Engineering, and Space Applications. There are two technical divisions: Space Operations and Engineering Support. Within the main campus are three centers for specific research: Space Utilization Research Center, Center for Planning and Information Systems, and Center for Advanced Spacecraft Technology. The last is involved in the development of technology to facilitate the transition to smaller, more capable scientific spacecraft. There are four facilities located apart from the main campus. Kagoshima Space Center has facilities for launching rockets, telemetry, tracking and command stations and optical observation. Noshiro Testing Center is used for propulsion research. Sanriku Balloon Center launches, monitors, and controls payloads carrying scientific balloons. The Usuda Deep Space Center (UDSC) is the location for the 64 m deep space antenna, which is capable of X and S-band operation.
There is a history of rocket development at ISAS for both satellite launch and sounding. The most recent and largest of ISAS's Mu series is the M-V, which is capable of lifting an 1,800 kg payload into LEO.
An example of the types of communications systems that are used by ISAS is that aboard the GEOTAIL spacecraft. This scientific satellite is monitoring earth's magnetosphere and was a joint ISAS-NASA project launched in 1992. The communication system, built under prime contract to NEC, comprises S and X-band systems for command, telemetry, and ranging. Spacecraft communication is compatible with both the UDSC and NASA's Deep Space Network.
Another fascinating and more recent satellite is the MUSES-B (Mu Space Engineering Satellite) or HALCA (Highly Advanced Laboratory for Communications and Astronomy) Space Very Long Baseline Interferometry (VLBI) satellite, launched in February 1997 aboard the first M-V rocket. The diagram of the onboard science subsystem is shown in Figure C.1. The satellite receives astronomical signals at 1.6 GHz, 5 GHz, and 22 GHz using the 8 meter diameter deployable antenna shown in Figure C.2 and built by Mitsubishi. The antenna is deployed using six extensible masts, which provide tension for the gold-plated mesh. The entire structure has a diameter of 10 meters and a mass of 247 kg. One of the experiments is to ascertain how reliable the surface tolerance is in space, particularly at 22 GHz. The non-cooled HEMT LNAs have noise temperatures of 35-40° K at 1.6 and 5 GHz, and 150° K at 22 GHz. Since there is no hydrogen maser onboard for precise time and frequency reference, this is accomplished using the Ku-band system shown in Figure C.1 for "phase transfer." TT&C is handled at S-band in a conventional manner.
Fig. C.1. HALCA payload diagram (Hirosawa and Hirabashi 1995).
Fig. C.2. MUSES-B spacecraft antenna deployment test
There is ongoing work in development of next-generation spacecraft technology. This covers a new concept in onboard computer architecture, a digital transponder, inflatable deployment mechanisms, data recorders with higher density memory devices, and lightweight star sensors. Lightweight nickel-metal hydride (Ni-MH) batteries are being developed for the LUNAR-A and PLANET-B missions. The new 15 Ah Ni-MH battery weighs less than 70% of the old Ni-Cd battery of the same capacity. Electric propulsion will be used in the MUSES-C mission in 2002.
ISAS has a very vigorous program in scientific and technical research for space science. As in the United States, such scientific endeavors are under intense scrutiny for budget cutting. Nevertheless, the staff at ISAS continues to look for innovative ways to develop more cost efficient systems, without compromising the science value of the missions.
Hayashi, Tomonao, et al. 1994. Japanese Deep-Space Station with 64-m Diameter Antenna Fed through Beam Waveguides and its Mission Applications. In Proceedings of the IEEE Vol. 82(5): 646-657.
Hirosawa, Haruto et al. 1996. Design and Development of the Space VLBI Satellite for VSOP (VLBI Space Observatory Programme). Space Technology Vol. 16(3): 161-167.
Hirosawa, Haruto and Hisashi Hirabayashi. 1995. VLBI Space Observatory Programme (VSOP) Satellite. IEEE AES Systems Magazine, June: 17-23.
ISAS. Annual Report (1995).
Yamada, Takihiro. n.d. Ground and Onboard Communication Systems for GEOTAIL. Handout.