Low Earth Orbit
Vast opportunities exist in space. Low earth orbit holds the potential to revolutionize technology, with LEO satellites able to connect the world in ways that have never seen before.
First, let’s explain the different types of orbits around Earth. Low earth orbit (LEO) is the closest to Earth. This ranges from 160 km to 2,000 km. After that comes medium orbit (MEO). The distance ranges from 2,000 km to 35,786 km. It is at this height that navigational satellites are most effective.
Geosynchronous orbits (GEO) follow the sidereal rotation of the Earth. At an altitude of more than 22,223 miles (36,000 kilometers), GEO satellites orbit the Earth at the same pace as Earth rotates: 24 hours for a complete rotation. Geostationary satellites fall into this category, which remain in orbit above a fixed point on Earth. A geosynchronous satellite is not necessarily a geostationary satellite. As a result of their elliptical orbits, some spacecraft drift east and west over a fixed point on the surface throughout a full orbit. It is possible for some satellites to have orbits that are not aligned with the planet’s equator. These orbital paths are said to have degrees of inclination. As a result, a full orbit of the satellite will take it north and south of Earth’s equator. For geostationary satellites to remain stationary, they must fly above the equator. There are several television satellites, communications satellites, and weather satellites that use geostationary orbits. The last is high earth orbit (HEO), which is anything above 35,786. There are only 56 satellites in high earth orbit, used for communications, satellite radio, and remote sensing.
The proximity of LEO to Earth makes it useful for multiple reasons. It is the most popular orbit for satellite imaging because of its proximity to the surface, which allows for higher-resolution images. This orbit is also used by the International Space Station (ISS), since it is easier for astronauts to travel between it and Earth. It takes a satellite in this orbit approximately 90 minutes to circle Earth at a speed of 7.8 km per second. At this speed, the ISS travels around Earth 16 times a day.
The closer they are to Earth, the faster their rotation around the Earth, and thus the smaller their communication field. As a result, more satellites are needed to provide coverage. Satellites in LEO often work together in constellations to provide continuous coverage. Constellations of satellites like this, consisting of several of the same or similar satellites, can often be launched together to create a ‘net’ around the planet. By working together, they can cover large areas of Earth simultaneously.
Almost 5,000 satellites currently orbit the Earth in LEO. In the next ten years, this number is expected to skyrocket. Many of those satellites are military, weather, and observational satellites. LEO satellites do not always follow the same path around Earth – their plane can be tilted to follow a different path. This allows satellites to use more routes, which is one of the reasons why LEO is so popular.
The proliferation of satellites in low Earth orbit, along with thousands more expected in the next few years, makes space debris a pressing concern. A space junk, or space debris, is composed of discarded launch vehicles or parts of a spacecraft that float hundreds of miles above the Earth, posing a collision risk with satellites.
The debris can also be caused by explosions in space or missile tests conducted by countries to destroy their own satellites. Several countries have shot down satellites, creating space debris, including Russia, China, the United States, and India.
Approximately 23,000 pieces of debris larger than a softball orbit the Earth, according to the U.S. government. One million pieces of debris are larger than one centimeter, and half a million are larger than one millimeter. It is estimated that 15 to 16 orbits of the Earth are made by debris every day, traveling at incredible speeds – about 15,700 miles per hour (25, 265, kph) in low Earth orbit – making collisions more likely and potentially severely damaging a satellite or spacecraft.
NASA estimates that debris in orbits below 600 kilometers will fall back to Earth within several years, but debris above 1,000 kilometers will continue circling for a century or more.
With so many satellites in orbit, the opportunities and possibilities are endless. Last year NSTXL saw several opportunities awarded for LEO projects. An $8.4 million contract was awarded to Tyvak by AFRL through SpEC for a Precise Space Flight Experiment. This prototype, released through the Space Enterprise Consortium (SpEC), will develop a spacecraft for new Very Low Earth Orbit missions with a plan to launch in 2024.
LEO Data Exploitation and Enhanced Processing (DEEP) prototype was awarded to Slingshot Aerospace through the Space Enterprise Consortium (SpEC) OTA vehicle managed by NSTXL. This prototype is meant to detect and mitigate radio frequency threats in contested air spaces. The fielding of new near-global, persistent proliferated Low Earth Orbit (pLEO) satellite constellations advances the scope to collect, process, exploit, and deliver satellite telemetry in ways not previously possible.
Another critical space orbit project – Space Mesh Networking End Crypto Unit (ECU) Prototype Project was also awarded last year, a new hardware and software prototype for space forces designed to protect large, interconnected satellite networks from cyberattacks.
Whether it’s maintaining space safety with a new technology or cleaning up space debris, NSTXL is prepared to help the warfighter in whatever capacity is needed. With members like SciTech, Leolabs, and Launcher in our network, NSTXL remains ready to take government innovation to the next level.