Relevance: GS-2: Science and Technology- developments and their applications and effects in everyday life. Environmental pollution and degradation.

Key phrases: LEO, constellation, GSO and GEO, Polar Orbit, Sun-Synchronous Orbit, International Space Station.

Why in News?

• Low Earth orbit (LEO) satellites, which quickly rose to prominence over the past couple of years as a cost-effective solution for satellite internet providers, may not be the most efficient solution for the field.

Context:

• Relying solely on LEO satellites to deliver connectivity would require massive investment and also cause major environmental concerns, Rajeev Suri, chief executive of British satellite communications firm Inmarsat, said at the 2022 Technology & Leadership Summit organized by the National Association of Software and Service Companies (Nasscom).
• A market estimate says that by the end of 2030, to support a constellation of more than 12,000 satellites, Starlink will need to have launched 23,000 satellites given the five-year lifespan. That is more than double the entire number of satellites launched by the entire world till date. This is a massive number.

Various orbit of Satellites:

• There are essentially three types of Earth orbits: High Earth Orbit (also called GSO and GEO), Medium Earth Orbit, and Low Earth Orbit.
  • A low Earth orbit (LEO) is, as the name suggests, an orbit that is relatively close to Earth’s surface. It is normally at an altitude of less than 1000 km but could be as low as 160 km above Earth – which is low compared to other orbits, but still very far above Earth’s surface.
  • Medium Earth orbit comprises a wide range of orbits anywhere between LEO and GEO. It is similar to LEO in that it also does not need to take specific paths around Earth, and it is used by a variety of satellites with many different applications.
  • It is very commonly used by navigation satellites, like the European Galileo system (pictured).
  • Geosynchronous Orbit (GSO) & Geostationary Orbit (GEO): Objects in GSO have an orbital speed that matches the Earth’s rotation, yielding a consistent position over a single longitude. GEO is a kind of GSO. It matches the planet’s rotation, but GEO objects only orbit Earth’s equator, and from the ground perspective, they appear in a fixed position in the sky. GSO and GEO are used for telecommunications and Earth observation.

  

Why Low Earth orbit is preferred?

• Unlike satellites in GEO that must always orbit along Earth’s equator, LEO satellites do not always have to follow a particular path around Earth in the same way – their plane can be tilted. This means there are more available routes for satellites in LEO, which is one of the reasons why LEO is a very commonly used orbit.
• LEO’s close proximity to Earth makes it useful for several reasons. It is the orbit most commonly used for satellite imaging, as being near the surface allows it to take images of higher resolution.
• It is also the orbit used for the International Space Station (ISS), as it is easier for astronauts to travel to and from it at a shorter distance.
• Satellites in this orbit travel at a speed of around 7.8 km per second; at this speed, a satellite takes approximately 90 minutes to circle Earth, meaning the ISS travels around Earth about 16 times a day.
• LEO satellites are deployed at orbits of 1,000km or less from the Earth’s surface and are typically smaller in size than most other types of satellites that offer satellite connectivity. This makes LEO satellites cheaper to build and deploy in orbit. They also offers much lower latency in terms of connectivity in comparison to geostationary earth orbit (GEO) satellites.

Issues with Satellite launching in LEO:

• The LEO environment is becoming congested with space debris because of the frequency of object launches. This has caused growing concern in recent years, since collisions at orbital velocities can be dangerous or deadly. Collisions can produce additional space debris. Ex. namely the infamous collision between satellites Cosmos-2251 and Iridium 33 in 2009 that created a huge cloud of debris.

• Communications satellites in LEO often work as part of a large combination or constellation, of multiple satellites to give constant coverage i.e. create a ‘net’ around Earth. However, GEO satellites do not require multiple units to be deployed to offer connectivity and can offer comparable bandwidth. GEOs also are capable of operating for around 15 years, against a five-year lifespan of LEO satellites.
• The issue of space junk and the reaction of aluminium with solar radiation because of LEOs in Earth’s higher atmosphere are also key concerns.
• Thousands of satellites and 1500 rocket bodies provide considerable mass in LEO, which can break into debris upon collisions, explosions, or degradation in the harsh space environment. Fragmentations increase the cross-section of orbiting material, and with it, the collision probability per time. Eventually, collisions could dominate on-orbit evolution, a situation called the Kessler Syndrome.
• Apart from the Adjacent Satellite Interference (ASI) which generates signal interference with spacecraft belonging to other orbital constellations, debris makes near space activities such as the missions to the International Space Station (ISS) as well as astronomical study of near space difficult.

Way forward:

• Reliance Jio, which recently announced its entry in the satellite internet space in partnership with European satellite operator SES, will use GEO and medium earth orbit satellites for its services is a good step towards connectivity and sustainability.
• The correct approach for a sustainable satellite connectivity service would be a hybrid one. Hybrid networks using GEO, LEO, and terrestrial 5G could be a simpler and more efficient way to meet customer needs. For instance, when in an aircraft, you don’t need online gaming, but might want high-speed connectivity but not low latency. In maritime operations, if there is a lot of network congestion and you don’t have enough bandwidth or capacity through GEO satellites, you can use 5G hotspots for this. LEOs would suit other areas, too.
• Regardless of whether the mega satellite constellations are developed and launched by states or commercial enterprises, they will have to jointly commit to reducing and mitigating the dangers posed by debris. Establishing an international convention that regulates the presence of satellites in LEO is another possible way in making LEO less congested and more sustainable for use.

Source: Live Mint  

Mains Question:

Q. “Satellite mega-constellations create risks in Low Earth Orbit, the atmosphere and on Earth”. Illustrate (250 words).