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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The orientation of a satellite in space is crucial, whether it be for telecommunications or Communivation observation craft, or for astronomy missions like XMM-Newton. After this, the de-spin system operates in order to make the TTCM subsystem antennas point towards earth station. In this method, we can stabilize the satellite by using one or more momentum wheels.

Power systems and rockets are present in this drum. If there is a change in altitude of the satellite, then the angles between the respective axes will be changed.

During launching phase, the satellite spins when the small radial gas jets are operated. Due to this, the spin axis gets stabilized and the satellite will point in the same direction. This set of three axis satelite the information about orientation of the satellite with respect to reference axes. These three axes define the altitude of satellite. Two types of transponder in use: Most satellite antennas are designed to operate in a single frequency band, for example, C band or Ku band.

Orbit control subsystem is useful in order to bring the satellite into its correct orbit, whenever the satellite gets deviated from its orbit. In this method, each axis contains two gas jets. In addition, a solar aspect angle within the range must be maintained at all times. 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”.

Satellites are of this type are called as spinners. OK Find out more about our cookie policy. The receiver-transmitter units are known as transponders. Given XMM-Newton’s very specific orbit highly elliptical, irregular eclipse seasons, Sun avoidancethis required very complex ln logic within the unit. This method is called as three-axis method. Missions Show All Missions. This drum is covered with solar cells.


A satellite which uses multiple frequency bands usually has four or more antennas. In this way, the AOC subsystem takes care of the satellite position in the right orbit and at right altitude during entire life span of the satellite in space.

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. Communication subsystem is placed on top of the drum.

Satellite Communication AOC Subsystem

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. The direction of this motor will be opposite to the rotation of satellite body, so that the antennas point towards earth.

The communication subsystem is the major part of the satellite. The letter use is housekeeping, since these subsystems serve aocd support the communications system.

ESA Science & Technology: Engineering

Likewise it will never point to within These forces change cyclically over a hour period, since the satellite moves around the earth. By continuing to use the site you are agreeing to our use of cookies. A vital requirement of the XMM-Newton mission is that its delicate science detectors must not be damaged by luminous sources in the sky. 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.


All eventual failures must be detected.

Before delivery for integration into the spacecraft, the AOCS system underwent several weeks of intensive testing, and subsequent System Validation Tests on the assembled satellite have confirmed its perfect operation. You can also try this books 1. 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 communicatiob satellite.

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. However, should any satfllite 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. Create your website today.

For redundancy XMM-Newton carries a second star-tracker telescope. The TTCM subsystem present at earth station monitors the position of satellite. If there is any change in satellite orbit, then it sends a signal regarding the correction to Orbit control subsystem.

The AOCS has also been designed to enable the satellite to operate in an autonomous mode for 36 hours, and during eclipses.

Satellite Communication – AOC Subsystem

The design of communiccation AOCS has been driven by a fail-safe approach. So, the second gas jet will stop the motion of satellite in that axis direction. These systems are partly on the satellite and partly at the controlling earth station. The pointing accuracy of the 10 m long XMM-Newton is 0. It is also used to control the antenna pointing and communication system configuration to suit current traffic requirements and to operate switch on the satellite.

Altitude control subsystem takes care of cojmunication orientation of satellite in its respective orbit.