Did you know that the orbit of the Hubble Space Telescope is changing, and due to this, its altitude is also decreasing? It is expected to return to the Earth’s atmosphere by 2030. Why is this?
This is because satellites change their orbit naturally. This occurs due to natural factors like atmospheric drag, solar radiations, and gravitational perturbations. However, some satellites can be made to change their orbits on demand. The satellite must be equipped with specific characteristics like propulsion systems and maneuverability.
To find out more, please continue reading.
Satellites
A satellite is any object in space and orbit, i.e., revolves around another bigger object. There are two types: natural satellites and artificial satellites. These two have their own specified purpose.
Types Of Satellite Orbit
Let us look into the three main types of orbits. All satellites are put into one of these and are expected to retain their orbit.
High Earth Orbit
Satellites in high earth orbit are at a distance of 42164 kilometers from the center of the Earth. When they reach this point in space, they find a comfortable position to be in and begin to orbit at the same speed at which the Earth orbits.
These satellites are called geosynchronous satellites.
Due to the speed of the satellite and the Earth being the same, the satellite seems to stay stationary at one longitudinal point on Earth. These satellites may still move North and South but do not move on the x-axis relative to the ground.
An example of a high-orbit satellite is the Geostationary Operational Environmental Satellite (GOES). Due to their constant ability to monitor one area, these satellites provide ample information about the weather conditions and environmental factors necessary to determine the weather.
Moreover, they are used for communication and monitoring solar activity.
Medium Earth Orbit
Compared to satellites with a high earth orbit, satellites with a medium earth orbit are closer to the Earth. There are two major types of medium earth orbit.
- Semi-synchronous orbit – This orbit is 26560 kilometers from the center of the Earth and is near-circular. The orbit takes 12 hours to complete and can move over one particular position twice. The semi-synchronous orbit is used for GPS satellites.
- Molniya orbit – To provide information about the Northern and Southern locations on Earth, satellites with a Molniya orbit are used. This moves in an extreme ellipse closer to the Earth from one end than the other. It takes 12 hours to complete one orbit.
Low Earth Orbit
These satellites are the closest to the Earth and are often visible from ground stations. They complete one orbit in approximately 90 minutes. These are essential for information about Earth observation, remote sensing, and scientific research.
However, low Earth orbit satellites are susceptible to damage due to the changes in the atmosphere and a higher risk of coming in contact with space debris and radiation. They require regular maintenance and damage repair to ensure they do not fall.
For further understanding, watch this Youtube video: Geostationary vs Geosynchronous vs Polar Orbits : UPSC.
Do Satellites Change Orbit?
Satellites are launched into space by rockets. These rockets carry the satellites, are launched quickly, and drop them in their desired location, where they move in their assigned orbit. Once these satellites find their assigned orbital positions, it is difficult to change orbit.
Satellites can change their orbits if they are built with maneuverability. However, this poses a high risk to the satellite, so it is usually not a common practice.
Typically, satellites stay in the orbit that they are designed for to fulfill the purpose that they are sent for. Orbit decay may occur, and the satellites may naturally change their orbit due to the factors surrounding them. We will discuss these later in the article.
Are All Satellites Able To Change Orbit?
For satellites to change their orbit, two important factors are required and must be built into their design to allow the satellite to do so. These are the satellite’s maneuverability and propulsion capability.
Maneuverability
When satellites are designed, their maneuverability is determined. Maneuverability refers to the ability of the satellite to adjust its position or change its orbit in space.
The weight, size, and purpose of the satellite determine how much it will be allowed to maneuver, and hence, some satellites are not allowed to maneuver the slightest, while others have much more space to do that.
For a satellite to be maneuvered, it requires adequate propulsion systems to assist it.
Propulsion
Propulsion systems are set in place to allow for satellite movement. These systems impact the satellite’s velocity and affect the orbit. There are three major types of propulsion systems, chemical, electric, and gravity assist.
Each system employs a different process to change the satellite’s acceleration. Chemical propulsion is used when satellites require quick acceleration; electrical propulsion is used when satellites need to function for longer durations, and gravity assist is used for satellites with low fuel reserves.
The satellite’s capability to change its orbit can be determined depending on the type of propulsion used and the satellite’s size.
Why Do Satellites Change Orbit?
Apart from the processes that the ground stations of satellites can control to change their orbits, all satellites are vulnerable to changes in orbit due to environmental conditions. Let us discuss these factors below.
- Atmospheric Drag – Air and gas particles are sparse in the space where satellites are launched, but some residues remain. These impose a slight drag on the satellite, causing it to move. The orbit moves out of its orbit over time.
- Solar Radiation – Solar radiation can exert pressure on objects in space. This pressure puts a small force on the satellite, but because the force is continuous, it makes the satellite change its orbit over time.
- Gravitational Perturbations – All celestial bodies have a gravitational force. When this pull force is constant, it can affect the orbit of any satellite.
These issues are counteracted with advanced systems in satellites which help keep the satellite in its original position. Moreover, thrusters may be introduced to increase the speed of the satellite and maintain its orbital position.
Final Thoughts
Scientists have long aimed at making satellites that stay in their orbit. Once this was achieved, they have now equipped satellites with mechanisms that allowed them to switch their orbit. With technological advances, this may become more common and easily attainable soon.
