Satellite Launch Vehicle
This tutorial section on satellite basics covers following sub topics:
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This page of satellite tutorial covers satallite launch procedure basics and describes steps involved in putting the satellite in its parking space.
The Satellite is used for various applications such as commnication, space and earth exploration etc.
The satellite is launched in the space with the help of launch vehicle.
It is used so that satellite will cross the earth's atmosphere as well as gravitational pull.
There are two types of launch vehicles viz. expendable type or reusable type. The expendable type of vehicles gets distroyed in space after placing the satellite in orbit. Ariane and Delta are expendable type of launch vehicles.
The re-usable type returns to the earth after leaving it at certain altitude above the earth. The examples of reusable type are GSLV and PSLV. Following are typical steps involved in a satellite launch procedure.
Navigation and guidance of the launch vehicle are important so that satellite can attain needed altitude, orbit path and essential kinematics requirements.
The satellite launch vehicle is a complex system and consists of following functional modules:
• Propulsion systems
• Auto Piloting
• Aerodynamic structure
• Interactive Steering subsystem
Satellite Launch Procedure
The four orbit stages involved in the satellite launch procedure are as follows:
1. Circular low earth orbit
2. Hohmann elliptical transfer orbit
3. Intermediate drift orbit
4. Circular Geostationary orbit
Figure depicts typical satellite launch procedure followed by space companies such as ISRO.
Following are the major steps involved in the launch process.
• Step-1: The launch vehicle takes the satellite into low earth orbit. The satellite is injected into desired 3-axes stabilized mode to achieve gyro condition using commands issued by launch vehicle to carry pyro firing.
• Step-2: After satellite reaches apogee AKM is fired for long duration to take satellite to intermediate orbit. This intermediate orbit is referred as transfer orbit. AKM is the short form of Apogee Kick Motor which contains liquid fuel.
• Step-3: The second apogee motor firing is carried out so that satellite attains needed angular velocity and acceleration for Geo-synchronization. This helps satellite to be in LOS from central earth stations. If required it is tracked through other countries earth stations.
• Step-4: Further stabilization and attitude control is achieved using control of momentum/reaction wheels. Antennas and transponders are turned on which brings satellite into stabilized geostationary orbit. Examples of geostationary satellites are INTELSAT, COMSAT, INSAT etc.
Once the satellite is placed in the parking space(i.e. designated orbit), following activities need to be performed
as part of maintenance.
• Orbit maintenance• Attitude maintenance• Thermal management• Power management• battery maintenance• Payload operations• Software requirement
Some of these operations are routine in nature whereas some are scheduled as and when required.