Dong Fang Hong 47

Launch data: Designation 25731 / 99025B Launch date 10 May 1999 - 01:33 UT Launch site Taiyuan Launch vehicle< CZ-4B(#54) Mission Scientific & Technology (Shijian) Sun-synchronous Earth orbit: Perigee / Apogee  870 km Eccentricity   Inclination  98.8 deg Period  102.35 min

Illustration of the deployed SJ-5 spacecraft (image credit: CAST)

Spacecraft data:

Description:

• SJ-5 is a Chinese scientific and technology demonstration satellite. It is the first modern small satellite of China with a new minisatellite platform, namely CAST968, designed and developed by CAST (Chinese Academy of Space Technology), while CSSAR (Center for Space Science & Applied Research) of CAS was responsible for the development of the payload and the ground application system. The overall objectives of the mission include:
  • Demonstration of advanced space technology experiments including the operation of multiple-mode attitude control, integrated onboard electronic system, a unified S-band TT&C system, S-band data transmitter, on-board data management system and large-capacity solid state storage.
  • Detection of SEU (Single Event Upset) and investigation of the corresponding countermeasures. In addition, dose measurment of the high-energy particles in the space environment
  • Demonstration of a space science fluid experiment.
• The main goal of the SJ-5 mission was to develop a modular minisatellite platform to be used for a number of different applications.

Mission details:

• SJ-5 represents the first minisatellite of China based on the modern CAST968 bus using a lightweight multifunctional aluminum honeycomb structure. The bus configuration resembles a box with overall dimensions of 1.2 m x 1.1 m x 1.04 m. The total deployed length of SJ-5 spacecraft is about 5 m.
• The ACS (Attitude Control Subsystem) features two modes of attitude stabilization, namely three-axis as well as spin-stabilized attitude control. The spin rate of the S/C is between 10-15 rpm during the spin control mode (a comparison of the two control modes is an experiment objective). Operations in spin control mode are being conducted about the axis of least inertia. The attitude measurement information is provided by a sun sensor and an infrared Earth sensor (pointing accuracy of < 0.5º, stabilization of < 0.005º/s). Actuation is provided by an offset momentum wheel, magnetorquers, and a cold-gas propulsion system (hydrazine). The 80386EX microprocessor system is used by the ACS.
• The following attitude modes are provided by the ACS:
  • The nominal mode for the science payload requires sun-pointing and spin stabilization. This is accomplished by spinning the S/C at 10~15 rpm with thruster augmentation, based upon sun sensor body rates.
  • The alternate mode for the science payload requires sun-pointing and three-axis stabilization. In this mode, the attitude is controlled using a bias-momentum wheel and three magnetic torque bars.
  • The Earth-pointing mode of the spacecraft employs three-axis stabilization. In this mode, the attitude is controlled using the technique of gravity gradient with a bias-momentum wheel and three magnetic torque bars, based upon a three-axis magnetometer. An Earth sensor is used for S/C Earth pointing.
• Thermal control is realized mainly by passive techniques. A redundant design is being used for key subsystems.
• The following technologies were introduced/demonstrated on the newly developed SJ-5 spacecraft bus, CAST968, offering greatly improved data handling and communication capabilities, in particular with respect to future Chinese satellites.
  • Use of a central computer and multiple management execution units located in each subsystem
  • An onboard CAN (Controller Area Network) bus is used; interface support of MIL-STD-1553B and RS-485 is provided
  • A large solid-state memory for data storage
  • The CCSDS (Consultative Committee for Space Data Systems) communication protocol standard with high-speed and multi-channel technology for repeated connection (data transmission between S/C and ground)
  • A high-speed data transmitter in S-band.
• The total S/C mass is 298 kg; the payload mass is 58 kg; an average power of 165 W is provided by the solar array of 3.4 m2 in size (hinged panel design). NiCd batteries of 17Ah capacity are used for power supply in the orbital eclipse phase. The S/C design life is three months.
  
  

  Schematic view of the CAST968 bus (image credit: CAST)

  
  
• RF communications: The spacecraft transponder was developed in China. Data transmission and tracking services are provided in S-band with 1 Mbit/s and 4 kbit/s downlink rates.
• Mission status: The science experiments were conducted during the first 3 months of the mission (until August 1999). Thereafter, various technology demonstrations and spacecraft attitude maneuvers (sun pointing, Earth pointing, etc.) were executed successfully. Spacecraft data were received until February 2000.
• The development of the modern CAST968 bus, utilizing an integrated electronic concept and a new manufacturing approach, provided in particular improved capabilities and brought the operational flexibility of the spacecraft system to a higher level of performance. - The same advanced bus concept is also being used on such follow-up missions as HY-1 (launch May 15, 2002), and on the spacecraft TC-1 and TC-2 of the DSP (Double Star Project), a joint CNSA/ESA science mission with launches in 2003 and 2004. All follow-up missions are operational as of 2006.

Sensor/experiment complement:

• There are 11 science experiments onboard, developed by CSSAR and by the Institute of Mechanics (joint program). The experiments or instruments are:
  • SEP (Single Event Phenomena) Monitor
  • SEP Shielding Experiment Device
  • SEU (Single Event Upset) Detector
  • SEP synthetical detector
  • SEL (Single Event Latch-up) Experiment
  • High-energy Proton / Heavy Ion Detector
  • High-energy Electron Detector
  • PMOS Dosimeter (a radiation dose detector).
• The eight instruments are used to measure the SEU effect and the high-energy particle environment. The observation of SEU, the investigation of the countermeasures and the measurement of the radiation in the space charged particle environment are more comprehensive compared with those in the SJ-4. With eight instruments, the investigation of SEU countermeasures includes almost all the methods known today. The measurement range of the energy spectra of the high-energy charged particles is the most completed so far, and the measurement of the radiation total dose is the first ever taken in china .The charges particles distributions in the abnormal area of the south Atlantic and in the subsiding areas of the two poles in the orbit have been obtained for the first time with the instrument developed by CSSAR. The collected data and the research results are significant for improving the design of space electronic instruments, raising the reliability and extending satellite's service life.