Satellite Launch Procedure | Procedure to launch satellite

This describes satallite launch procedure. It mentions various steps or procedure followed in order to launch satellite in its parking space.

The Satellite is used for various applications such as communication, 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 placing satellite 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 : These are mechanisms designed to generate thrust and propel a vehicle forward. There are various types of propulsion systems which include Jet Engines, Rocket Engines and Electric Propulsion.
•  Auto Piloting : Autopiloting refers to the capability of a vehicle to navigate and control itself without direct human input. Autopilot systems typically consist of sensors (like GPS and inertial sensors), a control system, and actuators (such as motors or servos) that manipulate the vehicle's controls (like ailerons, elevators, and rudders).
•  Aerodynamic structure : Aerodynamic structure refers to the design and shape of a vehicle to optimize its performance through the air or fluid. Wing design, fuselage shape, control surfaces (elevators, ailerons, and rudders), and other features contribute to the overall aerodynamics of a vehicle.
•  Interactive Steering subsystem : The interactive steering subsystem is a component of a vehicle's control system responsible for managing and responding to steering input. Components include the steering wheel, steering column, linkages, and the steering mechanism itself.

Satellite Launch Procedure

The four orbit stages involved in the satellite launch procedure are as follows:
1. Circular low earth orbit (LEO) : It is an orbit around the Earth which is characterized by its low altitude and circular shape. LEOs range from approximately 160 to 2000 Kms above the Earth's surface.
2. Hohmann elliptical transfer orbit : It is a specific type of elliptical orbit used for spacecraft transfer between two circular orbits. The transfer orbit is energy-efficient, requiring the least amount of propellant. It is elliptical, with one point in the initial orbit and the other in the final orbit. The spacecraft performs two engine burns: one to leave the initial orbit and enter the transfer orbit and another to leave the transfer orbit and enter the final orbit.
3. Intermediate drift orbit : An Intermediate Drift Orbit is an orbit that lies between a geostationary orbit and a Low Earth Orbit, typically characterized by a higher inclination than a geostationary orbit. Satellites in intermediate drift orbits do not remain stationary relative to Earth's surface but have a slower eastward drift. They are often used for communication satellites that cover specific regions without requiring the continuous high altitude of a geostationary orbit.
4. Circular Geostationary orbit : It is a circular orbit around 35,786 kilometers above Earth's equator, where satellites have an orbital period equal to Earth's rotation period, resulting in a fixed position relative to the Earth's surface. Satellites in GEO appear stationary in the sky, making them ideal for communication, weather monitoring, and Earth observation.

satellite launch-procedure

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 pyrotechnic (pyro) firing. Pyrotechnic devices are used to perform various functions, such as separating rocket stages, deploying payloads, or initiating specific actions during different phases of the launch.
➨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. An Apogee Kick Motor (AKM) is a type of rocket motor or propulsion system designed to perform the critical task of raising the apogee (the highest point in an orbit) of a satellite's trajectory. The AKM is typically used in geostationary transfer orbits (GTO) or other orbits where the satellite needs to reach a specific apogee altitude before circularizing its orbit.
➨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 earth stations in its vicinity.
➨Step-4: Further stabilization and attitude control can be 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.
Note: Some of these operations are routine in nature whereas some are scheduled as and when required.

The entire procedure involves a series of carefully orchestrated steps to transport a satellite from Earth's surface to its intended orbit in space. Overview of the same can be summarized as follows.
➨Mission Planning and satellite integration with the payload fairing.
➨Launch Vehicle Integration with encapsulated satellite
➨Transport of launch vehicle and payload to the Launch Site
➨Launch vehicle erection on the launch pad
➨Countdown of sequence of timed events
➨Ignition of rocket engines and lifting off of the launch vehicle from the launch pad
➨Ascent and Staging process
➨Orbital Insertion od satellite from payload fairing
➨Deployment of satellite into its intended orbit or trajectory
➨Payload Operations including deployment of solar panels, antennas and other structures, establishment of communication with ground stations etc.

Conclusion : Throughout the entire satellite launch procedure, ground control teams monitor the mission, and telemetry data is transmitted from the satellite to ensure its health and performance. The successful execution of each step in the launch procedure is crucial for the satellite to reach its designated orbit and fulfill its intended mission objectives.

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