May 1982:Japanese space exploration plans

Introduction

In 1981 Japan launched three satellites, covering scientific, technological and meteorological activities. The launchings are indicative of the aggressive programme of space satellite and launcher development which will, over the next few years, see Japan orbit ten more payloads with their own rockets from launch sites in Japan.

The development of satellites and launchers in Japan is divided between the Institute of Space and Astronautical Sciences (ISAS) of Tokyo University, and the National Space Development Agency of Japan (NASDA). ISAS is charged with the responsibility of preparing and launching small sci¬ entific satellites whilst NASDA looks after the development and procurement of large satellites to suit a number of the nation’s needs in the communications and meteorological fields. NASDA also handles the development of large launch vehicles (with US technical assistance) for orbiting these satellites.

Launchers

Currently, the Japanese satellite launch vehicles consist of the Mu-family, for orbiting scientific satellites, developed by ISAS, and the N-family, for orbiting applications satellites mainly to geostationary transfer orbit. NASDA is continuing the development of the H-1A rocket to meet the demand for launching larger satellites from the latter half of the 1980’s.

ISAS Launchers

The Mu-family has been successfully upgraded throughout the 1970’s. The current version is the Mu-3S which is a 23.8 m tall three-stage solid-propellant vehicle with eight small strap-on boosters around the base of the first stage. The Mu-3S is capable of placing about 300 kg into a low-altitude orbit. It features a full guidance and control capability by means of secondary fluid injection thrust vector control systems. The Astro-B and Exos-C satellites are currently scheduled to be orbited by this rocket.

The Mu-3S mod. 1 launcher is an improved version of the Mu-3S and also consists of three solid-propellant stages. However, at 28 m tall, it will have the capability of launching up to 670 kg into a low-altitude orbit through thrust augmentation of the second and third stage motors and the addition of two much improved strap-on boosters to replace the eight on the Mu-3S. Following launch of a test satellite to verify the performance of the vehicle, the Mu-3S mod. 1 will launch the Planet-A and Astro-C satellites. The test satellite is scheduled for launch in early FY 1984.

NASDA Launchers

NASDA’s Delta-class N-1 launcher is capable of placing about 130 kg into geostationary orbit. The first two stages are liquid fuelled while the third is a solid-propellant stage. Only one, carrying the ETS-3 satellite, remains to be launched. The N-2 launcher is capable of lifting about 350 kg into geostationary orbit due to the lengthening of the first stage (amongst other improvements). The H-1A launcher, being developed as a three-stage launcher with a liquid oxygen/liquid hydrogen second stage, will be able to place about 550 kg into geostationary orbit.

Satellites Planned for Launch

Since 1970, ISAS and NASDA have launched a total of 21 satellites. The plan for the period up to the end of FY 1985 envisages the launch of four scientific satellites, six applications satellites and one test satellite. In addition, ISAS is providing a principal investigator and major hardware for the Sepac project due to be flown aboard Spacelab 1.

ISAS’s 4 scientific satellites are:

Astro-B. The eighth scientific satellite is being prepared as a follow-on to the fourth scientific satellite Hakucho. It will perform two-dimensional imaging of celestial X-ray sources, including nebulae; galaxies and burst sources, with high temporal and spectral resolution. The box-shaped satellite is powered by four solar paddles and will weigh 180 kg. Launch is planned by mid-1982 into an orbit ranging from 350 to 600 km at an inclination of 31 degrees.

Exos-C. The ninth scientific satellite is an aeronomy satellite dedicated to the Middle Atmosphere Programme (MAP) of ICSU. From an altitude of between 300 to 1000 km, inclination 65 degrees, the satellite will observe phenomena in the stratosphere and the mesosphere (altitude 10 to 130 Km) using optical instruments. The data will allow further study of the ionosphere’s curious behaviour over the South Atlantic geomagnetic Anomoly which was found by the third scientific satellite Taiyo. Launch is planned for late 1983.

Planet-A. The tenth scientific satellite is to be launched into heliocentric orbit during FY 1984 to observe the interplanetary plasma in the inner regions of the Earth’s orbit as well as to take close-up ultra-violet images of Halley’s Comet during March 1986. The cylindrical satellite will weigh about 125 kg.

Asfro-C. The eleventh scientific satellite will be built to succeed Astro-B and will conduct more comprehensive studies in X-ray astronomy. The 400 kg satellite will be launched into a 500 km circular orbit during FY 1985. With its increased size and weight over Astro-B (although the box and four paddle shape will remain), the satellite will be able to observe more precisely the behaviour of celestial X-ray sources.

Sepac: The Space Experiments with Particle Accelerators experiment, developed by ISAS and NASA’s MSFC in association with the South west Research Institute in Texas, will carry out controlled active experiments on plasma by disturbing it with the injection of charged particles, accelerated by electron and ion beam accelerators, to generate aurora-like luminescences, waves, etc.

The six applications satellites planned fbr launch by NASDA are:

ETS-3. The third Engineering Test Satellite is intended to carry out tests on three axis attitude control, sola,r paddles and active thermal control in order to enhance the development ot technology common to satellites requiring a large amount of electrical power. Launch was planned on the final N-1 (number 7) in earls 1982. The 585 kg satellite should be put into a 1000 km circular orbit inclined at 45 degrees.

CS 2a and 2b. The Communications Satellites 2a and 2b are comparable to the Sukura Medium Capacity Communications Satellite launched in December 1977 which conducted experiments in satellite communications using quasi-millimeter waves (the first utilisation of these frequencies in satellite communications). The new satellites are to be launched into geostationary orbits at 112 degrees and 155 degrees E longitude in early 1985 and late 1985. CS 2b will act as an on orbit spare. Principal objectives lor the cylindrical 550 kg satellites are to offer domestic communications sets for public and official purposes and to develop technology for communications in satellites of the future.

BS-2a and BS-2b.

Broadcasting Satellites 2a and 2b are comparable to the Yuri Medium Scale Broadcasting Satellite for Experimental Purposes (BSE) which was launched m April 1978. This was a step towards a large scale broadcasting satellite system able to respond to growing demands ol TV broadcasting and able to beam signals to individual small TV receiver dish antennae. Yuri, with three transponders, operated for 27 months, giving excellent results. It is planned to launch BS-2a and BS-2b (the on-orbit spare) into geostationary orbit at 110 degrees E Longitude in early 1984 and mid-1985, respectively. The satellites, carrying equipment for the relay of two colour TV channels, are expected to eliminate poor TV reception areas and further develop direct satellite broadcasting techniques. The box-shaped satellites, with two solar paddles will weight about 550 kg each.

MOS-1. The Marine Observation Satellite, weighing about 750 kg, will be launched by a two-stage N-2 into a 99 degrees inclination Sun-synchronous orbit with a height of 909 km in early 1985. It will carry four instruments to study land and ocean surfaces. The most important experiment will use a multispectral Electronic Self-Scanning Radiometer to image the Earth’s surface at 50 m resolution using electronic charged coupled devices (CCD), the first time that such devices will have been carried on an Earth observation satellite. Other experiments involve a Microwave Scanning Radiometer, to observe sea-surface temperature and water vapour content of the atmosphere; a Visible and Thermal Infrared Radiometer and a Data Collection System to relay data from remote platforms collecting data on land and at sea. The box-shaped satellite has one large solar paddle.

Future Plans

ISAS is currently investigating a Mu-3S mod. 2 variant which, if funded, will launch a test satellite late in FY 1986. The first science payload for the new rocket would be the F.xos-D aeronomy satellite. Other projects studied by ISAS, but not approved, include an infrared telescope for use on the US shuttle, an ultraviolet survey satellite, an X-ray telescope satellite, a high energy solar physics satellite and two probes to Venus.

NASDA has many satellites under study, to be launched on the H-l A. These include an Earth resources satellite. JERS-1, carrying a synthetic aperture radar and other Earth sensing instruments. If funded, it will move Japan away from dependence on the US Landsat system. Planned orbit for the satellite is 350 km, inclination 98 degrees Sun-synchronous. Other satellites studied include an electromagnetic environment observation satellite, a geodetic satellite, more geostationary weather satellites (including a spare, GMS-3, to be available for launch after FY 1984), and large capacity experimental comsats.