Space-based physical sciences research

ONE of the seven short-term targets of China's white paper on space activities has to do with space-based basic research, an area where it has been active in recent years. The objective, according to the document, is to use the next generation of satellites beyond the present SJ series to strengthen the studies of micro-gravity, space material science, space life-science, space environment and space astronomy including pre-studies for lunar exploration.

Scientific missions form only a small part of the Chinese space programme so far. The most recent scientific mission was SJ-5, a small 398 kg satellite launched in May 1999. Its purpose was to study the terrestrial magnetosphere and single out upset events that damaged satellites in orbit. Experiments comprised a suite of cosmic ray detection instruments: semi-conductor proton and heavy ions detector, static electrical analyser, electrical potentiometer, static single event monitor and dynamic single event monitor. The mission lasted only a short period and ended in August 1999. Microgravity (10-4 - 10-5 g) experiments have been flown in the FSW-1 and -2 series and on SZ-4. The first materials science payload was flown aboard FSW-0 satellite in 1987. The experiments were related to smelting and recrystallisation of alloys and semiconductor materials like gallium arsenide. Experiments using high-temperature superconductor materials YBCO are also stated to have been carried out aboard FSW satellites.

One of the ambitious physical sciences projects is that of Solar Space Telescope being developed with German collaboration. This project began in 1992 for a 1-metre telescope to be launched in 2005. The telescope will have a polarising spectrograph, accompanied by four side-mounted telescopes to examine the sun in wide-band, X-ray, and hydrogen spectral lines. It will enable a study of solar magnetic field and solar flares as well as the space climate. Placed in a 800-km orbit, the 2-tonne telescope is expected to have a life of five years. The $60 m (0.5 billion yuan) telescope's resolution will be ten times better than the European Space Agency (ESA)/NASA Solar and Heliospheric Observatory (SOHO) spacecraft launched in 1995. China will pay about 80 per cent of the programme cost and is responsible for the primary instrument on the spacecraft to be jointly developed by the Chinese Academy of Space Technology and Chinese Academy of Sciences.

The main Chinese scientific project under way at present is the Double Star mission - comprising an equatorial and a polar orbiting satellite - done jointly with the ESA. The ESA has agreed to contribute 8 million euros to the mission. The first of the two missions will be this December. The mission is a successor to the European Cluster project, which is studying the effects of the Sun on the Earth's magnetosphere - the `magnetic bubble' that protects the earth from the worst effects of solar storms. Ten of the instruments are the same as Cluster, so as to provide comparable data from different angles, especially from the polar points from the second satellite that are not matched by Cluster. There are eight more Chinese instruments. Each satellite is 2.4 tonnes, to be launched by CZ-2C. The equatorial satellite will fly in a 550-60,000 km orbit inclined at 28.5o to the equator while the polar satellite will fly from 350 to 25,000 km at 90o. The orbits are lower than Cluster and will keep Double Star mainly inside the magnetosphere.

Double Star will conduct a number of scientific investigations, most of which will augment measurements coming from the four Cluster satellites. The equatorial-orbiting satellite, which will be launched in December, will investigate the earth's huge magnetic tail, the region where particles are accelerated towards the polar regions by a process known as magnetic re-connection. When these particles reach the earth, they can cause power cuts, damage satellites and disrupt communications. The other (polar) satellite, which is slated for June 2004, will investigate physical processes taking place over the magnetic poles and the development of aurorae.