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What is a Low Orbit Satellite?

It’s easy to think that satellites are more effective the higher they go into space, but this is not always the case. Indeed, among the most popular ways to put satellites into advantageous positions is that of low Earth orbit.

A low orbit satellite can serve many important roles that are just as crucial as those performed by satellites in the lofty heights of medium Earth orbits or geostationary orbits. Here we examine our closest orbit and identify its strengths.

What satellites are in low Earth orbit?

A great number of satellites are held in low Earth orbit (LEO) and this is due to the advantages of such a relatively close proximity to the planet. ‘Relatively’ is a key word, because an LEO satellite could be merely 160km above the Earth’s surface or as much as 1,000km.

LEO is ideal for satellites that exist with the mission of photographing or recording footage of the Earth’s surface. Being closer allows for higher resolution images from a substantial vantage point while minimising obfuscation.

Low orbit satellites are not bound by the need to exist on a specific plane like those in geostationary orbit (GEO), which must follow the Earth’s equator. As a result, LEO gives satellites the flexibility to be launched into different orbital inclinations while being able to perform their roles in more or less the same way.

LEO is not ideal for tasks that require constant tracking, however, such as traditional way of handing telecommunications. This is due to a combination of their close proximity and high speed of travel, making them difficult for ground stations on Earth to lock on to and maintain a link with. However, recently there has been a boom in potential telecommunications (IoT in particular) from low Earth orbit, with companies such as Kepler, Fleet, Huber and others building pilot constellations ofminiaturised satellites.

It is these smallsats that  are typically placed into LEO.

These low orbit satellites are cost-effective and versatile; however, they have limited lifespans. Many smallsats are designed to last a handful of years at most, and need constant replenishment if constellation upkeep is a factor. Some flight software solutions for these satellites have adapted to this need, eliminating the need to develop a brand new package from scratch every time one of these satellites is completed and prepared for orbit.

How many low earth orbit satellites are there?

According to the UCS Satellite Database, it is thought that just over 4,000 satellites are in LEO. However, it can be difficult to get a full and accurate picture of how many satellites are in Earth’s orbit due to the sheer number being launched every year.

Indeed, 2021 saw an incredible rise in the number of satellites leaving Earth, just shy of a 42 per cent year-on-year increase. Combine that with the number of satellites reaching the end of their useful lives and becoming inactive, as well as unregistered satellites finding ways to get into space regardless of regulatory challenges, and attempting to find the true number of active satellites in orbit yields differing results.

The number of low orbit satellites can certainly be expected to increase at a considerable rate in the coming years. Companies like OneWeb and the SpaceX-operated Starlink are current frontrunners in LEO satellites, the latter using them to establish competitive 5G networks and broadband services. However, they face competition from others – particularly nations who are determined not to fall behind in space presence, like China.

With that in mind, is thought that as many as a further 7,000 LEO satellites could be seeing their launches over the next decade.

How long can a satellite stay in low Earth orbit?

Many satellites in LEO are smallsats, meaning that while LEO isn’t reserved for these more compact craft, it is heavily populated with them.

As such, given the lifespans of these smaller spacecraft and the limited resources they have at their disposal, LEO isn’t always a long-term endeavour.

Depending upon where a satellite falls in the spectrum of LEO space, it could stay up for mere months or for potential decades. A middling lifespan for many smallsats in LEO is around three to five years. It depends on the altitude of the satellite in question and its velocity. Too close to the Earth means encountering thicker atmospheric layers which create drag and cause orbital decay, slowing the satellite and making the gravitational pull of the planet more effective.

The International Space Station, which maintains a low orbit of roughly 400km, is continually losing velocity and altitude due to atmospheric drag. It’s thought to lose up to 100 metres of altitude and 5cm/s of velocity per day. In order to sustain LEO, it must briefly use its thrusters to regain lost altitude about once a month. Without this help, the ISS would have likely long lost its orbit.

Satellites in higher orbits like GEO can sustain their distances for many, many years, but low orbit satellites are likely to struggle in the long term. Whereas GEO satellites are moved further away from Earth into a ‘graveyard’ orbit when they reach the end of their life, LEO satellites are too close to be moved so far and instead are expected to enter Earth’s atmosphere and burn up, leaving no debris or parts on the ground.

Can I put my own satellite into low orbit?

Harnessing miniaturisation and standardisation of electronics, smaller, yet very capable satellites can now be launched in higher volumes for lower cost. With the appropriate off-the-shelf hardware and software, smallsat missions have never been more accessible. Bright Ascension’s Flight Software Development Kit has been built from the ground up to create a component-based architecture for quick and cost-effective mission development. Choose from a library of pre-validated software pieces that help you to build your mission-specific software easily and repeatably, getting your satellite ready for orbit faster than ever.

Learn more: Book a demo

We run regular demo sessions for our Flight Software Development Kit and Mission Control Software that you can book at any time. These are group sessions but you can join anonymously and participate as much or as little as you like. Book demo today.