AOCS IN SATELLITE COMMUNICATION PDF

The attitude and orbit control subsystem (AOCS) provides attitude information communications service equipment, and scientific instruments. Control is. An operating communications satellite system consists of Physical Structure. Attitude and Orbit Control System. (AOCS). Power System. Thermal Control. oriented framework for Attitude and Orbit Control System or AOCS of satellites. Understanding the case study requires some familiarity with the AOCS domain.

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If there is any change in satellite orbit, then it sends a signal regarding the correction to Orbit control subsystem. So, the second gas jet will stop the motion of satellite in that axis direction. The orientation of a satellite in space is crucial, whether it be for telecommunications or Earth observation craft, or for astronomy missions like XMM-Newton. In this method, we can stabilize the satellite by using one or more momentum wheels.

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In this method, each axis contains two gas jets. From then on, the X-ray observatory’s life in space, for more than ten years, has been beating to the rhythm of its “electronic heart”. The satellites, which perform this kind of operation are called as de-spin. Power systems and rockets are present in this drum. The TTCM subsystem present at earth station monitors the position of satellite. Based on telemetry data received from the satellite and orbital data obtained from the tracking system, the control system is used to correct the position and attitude of the satellite.

These forces change cyclically over a hour period, since the satellite moves around the earth. An electric motor drives this communication system.

A satellite which uses multiple frequency bands usually has four or more antennas.

Create your website today. This subsystem consists of rocket motors that are used to move the satellite back to the correct orbit when external forces cause it to drift off station and gas jets or inertial devices that control the attitude of the satellite.

On the basis of data supplied by a star-tracker telescope, which recognises the different star formations in its field of view, the AOCS computers calculate the appropriate momentum of the reaction wheels for precision manoeuvring of the spacecraft during observations or to change the target. This drum is covered with solar cells. The second gas jet will be operated for same period of time, when jn satellite reaches to the desired position.

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Satellite Communication – AOC Subsystem

Then, it satelite resolve that issue by bringing the satellite into the correct orbit. Following are the two methods to make the satellite that is present in an orbit as stable. Orbit control subsystem is useful in order to bring the satellite into its correct orbit, whenever the satellite gets deviated from its communicaation. They will provide the rotation in both directions of the three axes. The fully redundant AOCS represents some kg of electronics: Note that this is not a bright source avoidance cone, but driven by requirements on the spacecraft’s alignment with respect to the Sun to ensure sufficient energy supply and thermal stability.

This method is called as three-axis method. Learn all you need in order to create a. The AOCS has also been designed to enable the satellite to operate in an autonomous mode for 36 hours, and during eclipses. It is also used to control the antenna pointing and communication system configuration to suit cokmunication traffic requirements and to operate switch on the satellite.

The receiver-transmitter units are known as transponders. It is usually composed of one or more antennas, which receive and transmit over wide bandwidths at microwave frequencies, and a set of receivers and transmitters that amplify and retransmit the incoming signals. It is responsible for the detection of anomalies of whatever origin and their correction.

Spinner contains a drum, which is of cylindrical shape. However, should any serious anomaly occur, such as a prolonged loss of contact, XMM-Newton will automatically enter a survival mode and wait for direct control to be re-established from Earth.

All communications satellite derive their electrical power from solar cells.

AOC subsystem is helpful in order to make the antennas, which are of narrow aocw type points towards earth.

These three axes define the altitude of satellite. The letter use is housekeeping, since these subsystems serve to support the communications system. Two types of transponder in use: All eventual failures must be detected. Most satellite antennas are designed to operate in a single frequency band, for example, C band or Ku band.

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The design of the AOCS has been driven by a fail-safe approach. Given XMM-Newton’s very specific orbit highly elliptical, irregular eclipse seasons, Sun avoidancethis required very complex hardwired logic within the unit.

Attitude and orbit control system(AOCS) | Satellite Communication

Altitude control subsystem takes care of the orientation of satellite in its respective satelllite. These systems are partly on the satellite and partly at the controlling earth station. If there is a change in altitude of the satellite, then the angles between the respective axes will be changed.

After this, the de-spin system operates in order to make the TTCM subsystem antennas point towards earth station. ESA’s X-ray space observatory targets distant X-ray sources for long periods often exceeding ten hours and one of the key requirements of the satellite is its very high pointing accuracy and stability.

ESA uses cookies to track visits to our website only, no personal information is collected. In addition, a solar aspect angle within the range must be maintained at all times. The telemetry system sends data derived from many sensors on the satellite, which monitor the satellites health, via telemetry link to the controlling earth station. The power is co,munication by the communications system, mainly in its transmitters, and also by all other electrical systems on the satellite.

Communication subsystem is placed on top of the drum. A vital requirement of the XMM-Newton mission is that its delicate science detectors must not be damaged by luminous sources in the sky.

Let X, Y and Z are another set of Cartesian axes. Due to this, the spin axis gets stabilized and the satellite will point in the same direction.

We know that satellite may deviates from its orbit due to the gravitational forces from sun, moon and other planets.

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