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Space


China and Geophysics Research

When starting to develop satellites, China began to develop the series of scientific detection and technological test satellites to make the advanced test of new technology badly needed for space mission, and carry out space environment monitor and space scientific research. Since the 1970s, China has developed and launched the SJ-1 and SJ-2, SJ-4 and SJ-5 satellites, which formed the preliminary series of the SJ scientific detection and technological test satellites.

Shi Jian (Practice) 1

The SJ-1 was successfully launched on March 3, 1971. The satellite was placed into an orbit with an apogee of 1826km, a perigee of 266km, inclination of 69.6 and orbit period of 106 min. Its similarly spherical structure with a diameter of 1m was completely covered. There are 14 pieces of silicon solar cell mounted on the trapezoidal planes of upper and lower hemispherical shells. The satellite used the spin-stabilized attitude control system. In the middle of the satellite there is a circular pressurized capsule with short-wave telemetric instruments and the ultrashort- wave beacon transmitter and receiver, and silver-zinc chemical battery. Between the main capsule and outer case there are four auxiliary capsules. They are auxiliary capsule 1 with two sets of nickel-cadmium (Ni-Cd) batteries and small telemetry equipment in it, auxiliary capsule 2 with the limiter and the phase-shifting adjuster network in it, auxiliary capsule 3 with a 5cm responder in it and auxiliary capsule 4 with a 10cm beacon machine.

There were two scientific payloads in the satellite: the G-M counter and BE window integrating ionization chamber. The G-M counter was used for detecting cosmic rays and measuring the total flux of protons with energy of more than 16.4 MeV and the total flux of electrons with energy of more than 0.88MeV. The BE window integrating ionization chamber was used for exploring solar X-rays with measuring wavelength being (1-8)10-2?.

The task of the space technology test of the SJ-1 satellite was to make the long-term space test of satellites basic technology and systems mainly including silicon solar sell and Ni-Cd battery system, the passive-active thermal control system, and the remote control system.

The SJ-1 operated normally and properly for 8 years -- far more than one year designed lifetime. It was few in foreign satellites developed in the 1960s. The SJ-1 provided valuable experiences for the development of satellites with long lifetime. And the long-term power supply system, long-term thermal control system and long-term telemetry system of the SJ-1 satellite won Achievement Prize of the National Science Congress in 1978.

Shi Jian (Practice) 2

Geophysics research on satellites has not been given many opportunities by PRC officials. The first notable experiments in the field were conducted by the Shijian-2 satellite, one of a trio of satellites launched on a single booster on 20 September 1981 along with Shijian-2A and Shijian-2B, when charged particle detectors were included in the multi-discipline scientific payload. The initial 235 km by 1,600 km orbit limited the data collection period to less than one year. The SJ-2 satellite fleet includes the SJ-2, SJ-2A and SJ-2B. On September 20, 1981 China launched these three satellites on one rocket for the first time, which marked a new breakthrough in space technology.

The weight of the SJ-2 is 250kg, operating in an orbit with an apogee of 1600km, a perigee of 240km and inclination of 50.5? The main body of the satellite is an octahedral pyramid with a circumscribed circle diameter of 615m. On the top of the satellite, the four sides are equipped with four movable solar wings and the other four are equipped with blinds, spinning stabilized toward the sun. There are four explosive bolts with a diameter of 16 mm connected with the launch vehicle.

Two main tasks of SJ-2 were to detect space physical environment parameter, and to test new technology for the satellite, mainly using the solar panel to supply power for satellite instruments, spin stabilized and directing towards the sun attitude control, the magnetic core memory and delayed telemetry and control technology, ultrashort-wave unified system with tracking and telemetry common use radio channel and passive-active thermal control system for the whole satellite and for the first time using several blinds adjust the temperature of the whole satellite.

Shi Jian (Practice) 2-A

The SJ-2A satellite is a beacon transmitter satellite used for the detection of the ionosphere. The mass of the satellite is 480kg, using the silver-zinc cell. High frequencies of the beacon transmitter are 162 MHz and 40.5 MHz. The former one was used for tracking. The principle of the measurement is that the ground station receives Doppler shift and Faraday spin of the two signs passing through the ionosphere to inverse the integrated electronic concentration of the ionosphere.

Shi Jian (Practice) 2-B

The SJ-2B is a passive radar calibration test satellite. A balloon with a diameter of 4m was used as a guiding optical beacon connected with a metal ball with a diameter of 0.45m by a 600m silk rope, which was used for the radar's calibration.

The balloon would expand after it was placed into orbit because of sublimate and a little residual gas in it. The polyester aluminum plated surface of the balloon was very bright and guided the radar to find the metal ball. In the first 16 rounds in the orbit, Kashi station for 7010 radar and Zijinshan Observatory acquired 5 targets in orbit and successfully carried out the radar calibration.

Shi Jian (Practice) 4

Chinese scientists did take advantage of the first test flight of the CZ-3A launch vehicle on 8 February 1994 to deploy the 400-kg Shijian-4 spacecraft. Placed into a GTO of 212 km by 36,092 km with an inclination of 28.6 degrees, Shijian-4 carried proton and electron detectors and a single event upset (SEW) monitor to return geophysical data. The spacecraft was spin-stabilized (10-20 rpm) and employed conventional, body-mounted silicon solar cells and NiCd batteries for the electrical power system (Reference 61).

The SJ-4 was used to detect the space radiation environment and radiation effect. In order to detect the geosynchronous transfer orbit environment the SJ-4 had a specially designed a space radiation environment and radiation effect test project. Three instruments were designed for the space radiation environment and radiation effect test project, including a satellite surface potentiometrer and two single particle effect testers (one single particle static monitor and one single particle dynamic monitor). The working principle of the single particle static and dynamic monitors is as follows: They make the self-checking with the computer's normally working program, check their operation, record faults position and accident time, and correct errors line by line to maintain proper operation. And the system has the ability to restart and record accident time when meeting faults of the whole machine.

Shi Jian (Practice) 5

The SJ-5satellite was launched into an 870 km similar circle orbit on May 10, 1999. The satellite was designed to operate normally in orbit for three months and carry out a two-layer scientific experiment in microgravity environment, new technology demonstration experiment, and the detection and countermeasure research of the single particle. According to the preset sequence the SJ-5 was launched, tested in orbit, transferred, managed for a long time and tested for lifetime.

The mass of the SJ-5 satellite is 30kg. Its structural configuration is a cube with each side of length being nearly 1.2m when the solar panels are folded and its wingspan is 5m when the solar wings deploy. The satellite was composed of such subsystems as the mechanism and construction, thermal control, attitude control, housekeeping, power and system circuit, measurement and control, antenna, and payload.

Chinese Academy of Space Technology (CAST) is devloping a small satellite bus for science and earth observation missions. The first two satellites based on this bus are Shijian-5 (SY-5) and Haiyang-1 (HY-1 or Ocean-1). Both satellites weigh 340kg and have two solar panels. With 11 science payloads onboard, SJ-5 will test 3 different kinds of attitude control methods: 3-axis, spin and gravity-gradient.




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