Satellites are used for many purposes, but where do they stay to achieve them? Today, we’ll find out about the different orbits that satellites use.
Low Earth Orbit
One of the most populous regions for satellites is the low Earth orbit, which is the region in space relatively close to Earth. However, the term “relatively close” can be ambiguous, as the low Earth orbit spans to 2000 kilometers above Earth according to NASA, and 1000 kilometers from our planet according to ESA.
There is one main reason why missions choose to put satellites so close to our planet. It is easier to get from Earth to low Earth orbit than to anything farther from the globe because less delta-v (acceleration) is necessary. The less the required acceleration, the less fuel is needed to launch anything to the desired orbit, and the lower the cost of the mission, given that all other variables are identical. Thus, by default, satellites launch to low Earth orbit unless another location is better.
Due to the relatively high density of abandoned defunct satellites in this region, space debris is the most prominent issue there. The Kessler syndrome, an unstoppable chain reaction between space debris collisions, is the most likely to occur there, preventing anything from launching beyond the cloud of small pieces of garbage.
Further out, there is the geostationary orbit, which is about 35786 kilometers above Earth. The attractive thing about it is that the orbital period of a satellite in this orbit is precisely the rotation period of our planet. This property makes it suitable for satellites that need to consistently stare at a small patch of the Earth, such as communication satellites or weather satellites.
Nevertheless, the downside of this orbit is that it is hard to observe the polar regions using it. This is because if any inclination is introduced to the orbit, the view from the satellite to the Earth is not motionless, and the purpose of the spacecraft may not be well-achieved.
If a mission wants the spacecraft’s trajectory to cover the entire globe, choosing a polar orbit is a great idea. By orbiting perpendicular to Earth’s rotation, the trajectory eventually traverses the whole planet as it rotates. As the last sentences suggest, the satellites using this kind of orbit are usually global observation satellites.
A special type of polar orbit, called a sun-synchronous orbit, keeps the orbit in sync with the Earth’s rotation such that it passes through the same latitude at the same time of the day. This is very useful for satellites that observe multiple locations intermittently while keeping them in low Earth orbit instead of geostationary orbit.
In this article, we’ve mentioned 3 types of orbits where satellites commonly orbit our planet. If you want more information about where satellites orbit Earth, please visit the webpages in the references below.
References and Credits
- (2020, March 30.). Types of orbits. Retrieved April 20, 2022, from https://www.esa.int/Enabling_Support/Space_Transportation/Types_of_orbits
- (n.d.). LEO Economy FAQs. Retrieved April 20, 2022, from https://www.nasa.gov/leo-economy/faqs
- (n.d.). What is a solar sun-synchronous orbit? Retrieved April 20, 2022, from https://www.futurelearn.com/info/courses/observing-earth-from-space/0/steps/245745
- Howell, E. (2015, April 24). What Is a Geosynchronous Orbit? Retrieved April 20, 2022, from https://www.space.com/29222-geosynchronous-orbit.html