SHI JIAN 2

Shi Jian 1, in March 1971, was China’s first scientific satellite and highly successful (Chapter 1). It was eight years before China was again ready to launch scientific satellites. This time, the Chinese attempted to launch three satellites in one go. This was by no means unusual, for the Russians had pioneered three-in-one launches in 1964 and had even launched eight-in-one missions (coincidentally, the first taking place the day after Dong Fang Hong was put into orbit in 1970). This is not to minimize the achievement, for the deployment of three scientific packages in this manner can often be accident-prone (as more advanced space nations have sometimes been reminded, to their cost). The original Shi Jian 2 project dated to 1972, when it was defined as a single space physics satellite to cover eight fields of work. In the course of refinement, three more areas were added, with design concluded by the end of 1974. An extensive instrumentation package was prepared (Table 7.1).

Table 7.1. Shi Jian 2 instruments.

Magnetometer

Semi-conductor electron unidirectional intensity detector Semi-conductor proton unidirectional intensity detector Semi-conductor electronic directional probe Scintillation counter

Four-channel long-wave infrared radiometer Two-channel short-wave infrared radiometer Earth atmosphere ultraviolet background radiometer Solar ultraviolet radiometer Solar soft x-ray proportional counter Thermoelectric ionization barometer

The orbit was planned for 250-3,000 km, inclination 70°, with an operational lifetime of six months. Shi Jian 2 was a 257-kg, eight-sided, 1.23-m-diameter prism, 1.1m high, with four small solar panels. The Shi Jian 2 had a single ultra-short-wave transmission system at 40.5 MHz and 162 MHz, and would send back telemetry both in real time and by tape recorder able to hold 520,000 bits of data at a time. It was the first Chinese satellite to store information for later retransmission, being dumped to ground stations during overpasses of China, and was the first Chinese satellite to use solar panels (as distinct from solar cells attached to the main body of the spacecraft, like Shi Jian 1). Each panel was 1.14 m long and 0.56 m wide, making a total span of 2.55 m2. The four solar panels contained 5,188 small solar cells, generating 140 W, which charged nickel cadmium batteries. It was the first Chinese satellite to have a full solar orientation system to point it towards the Sun and thereby obtain maximum solar power to support the electric demands of the scientific instruments. A hydrazine-fueled thruster system would keep the satellite’s panels pointed towards the Sun, rotating the spacecraft at 15-20 revolutions per minute. Shi Jian 2 made extensive use of the louver system of thermal control so successful on Shi Jian 1. The satellite represented a substantial advance in satelhte design.

Although originally intended for launch on the Long March, it was calculated that, if the Feng Bao launcher were used, it would be possible to lift two other satellites at the same time, although this also meant an alteration to the orbit, to 59.5°, 240-2,000 km. The first Chinese three-in-one launch came to grief and failed to reach orbit on 28th July 1979 when the Feng Bao’s second-stage vernier engine, designed for the final low-powered thrust to orbit, failed. There was a spare Shi Jian 2, but the other two satellites had to be built from scratch.

A fresh attempt was organized and Shi Jian 2, 2A, and 2B were put into orbit in darkness on 19th September 1981. No fewer than 59 separate operations had to be carried out perfectly in sequence for the separation procedure to work – and it did. The scientific satellites entered similar orbits: 232-1,615 km, 59.5°, 103 min. The other two satellites were entirely different: Shi Jian 2A, the main one, was heavier, bell-shaped, with two cones and antenna, while Shi Jian 2B was a combined metal

ball and balloon, linked by a thin wire and designed to measure decay rates due to atmospheric drag. The three satellites operated for 332, 382, and six days, respectively. Shi Jian 2 provided details of the configuration, distribution, and boundaries of the Earth’s radiation belts. By flying during the period of an 11-year peak of solar activity, it was able to measure radiation from our Sun at its most violent and enable predictions of solar storms to be made.