Satellite Launching Procedure and Processes

This comprehensive guide covers each step of the satellite launching process, from initial planning and selecting the right launch vehicle to executing the launch phases and deploying the satellite into its intended orbit.

Understanding the satellite launching procedure helps in optimizing the satellite’s functionality and lifespan, ensuring mission success. Satellites are used for various applications such as communication, space, and earth exploration.

The satellite is launched into space with the help of a launch vehicle. This is essential so that the satellite can cross the Earth’s atmosphere and overcome gravitational pull. There are two types of launch vehicles: expendable and reusable.

Expendable vehicles are destroyed in space after placing the satellite in orbit. Ariane and Delta are examples of expendable launch vehicles. Reusable vehicles return to Earth after placing the satellite at a certain altitude. GSLV and PSLV are examples of reusable launch vehicles.

The following are typical steps involved in a satellite launch procedure. Navigation and guidance of the launch vehicle are critical so that the satellite can attain the needed altitude, orbit path, and essential kinematic requirements.

The satellite launch vehicle is a complex system and consists of the following functional modules:

• Propulsion systems: These are mechanisms designed to generate thrust and propel a vehicle forward. There are various types of propulsion systems, including 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 Process

The four orbit stages involved in the satellite launching procedure are as follows:

1. Circular Low Earth Orbit (LEO): It is an orbit around the Earth 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.

Figure depicts typical satellite launch process followed by space companies such as ISRO.

The 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 the desired 3-axes stabilized mode to achieve gyro condition using commands issued by the 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 the satellite reaches apogee, AKM is fired for a long duration to take the satellite to an intermediate orbit. This intermediate orbit is referred to as a 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 the satellite attains the needed angular velocity and acceleration for Geo-synchronization. This helps the 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 the satellite into a 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), the 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. An 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 of the satellite from the payload fairing
• Deployment of the 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 launching 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 satellite launch process is crucial for the satellite to reach its designated orbit and fulfill its intended mission objectives.