SpaceX’s Starlink is currently a hot topic. So, let’s try to understand in depth what is all about.
So, what is this satellite internet all about?
Satellite internet is internet access provided through communication satellites. They work on different frequency bands such as L (1-2 GHz), C (4-8 GHz), Ku (12-18 GHz), Ka (26.5-40 GHz). Frequency bands are chosen depending upon the usability, range, data transmission speed, power capability, intended cost of satellite, etc. For e.g: a higher frequency Ku band can achieve a high download speed of nearly 500 Mbps (bits and not bytes) such speeds are not possible for low-frequency bands.
In the early-stage satellite internet sector, Teledisc was a prominent aspirant. Its idea was to create a broadband satellite constellation of hundreds of low-orbiting satellites in Ka frequency band, to provide low-cost internet access. From 2010 onwards, high throughput satellites such as ViaSat-1, Jupiter, etc. have achieved further improvements.
Now as we saw in our previous article, there are different orbits in which satellites can be placed. Let’s understand the pros and cons of communication satellites placed in these orbits.
Due to the fixed nature of geostationary orbit, the antennas at the ground need not move to constantly track them. But one major drawback is latency (delay between requesting data and receipt of response). If all other signaling delays could be eliminated, it still takes a radio signal about 250 milliseconds (ms), or about a quarter of a second, to travel to the satellite and back to the ground.
Factoring in other normal delays from network sources gives a typical one-way connection latency of 500–700 ms from the user to the ISP, or about 1,000–1,400 ms latency for the total round-trip time (RTT) back to the user. This is more than most dial-up users experience at typically 150–200 ms total latency.
Medium Earth orbit (MEO) and low Earth orbit (LEO) satellite constellations do not have such great delays, as the satellites are closer to the ground. For e.g: The current LEO constellations of Globalstar and Iridium satellites have delays of less than 40 ms round trip. Unlike geostationary satellites, LEO/ MEO satellites do not stay in a fixed position in the sky. Consequently, ground-based antennas cannot easily lock into communication with anyone specific satellite. Therefore, multiple satellites are necessary to establish a permanent internet connection.
Since 2014, many companies announced developing satellite internet constellations in LEO such as SpaceX (Starlink), OneWeb, Amazon (Project Kuiper), Facebook (Athena). Many planned constellations deploy laser communication for inter-satellite links to effectively create a space-based internet backbone.
Now coming specifically to Starlink; Starlink is a key part of Elon’s long-term plan to help humanity colonize Mars. SpaceX hopes to use Starlink revenue to fund the development of Starship and Super Heavy. SpaceX says each satellite will be “capable of tracking on-orbit debris and autonomously avoiding collision,” and that 95 percent of the satellites’ components will quickly disintegrate in Earth’s atmosphere at the ends of their lifetimes.
Though International Astronomical Union (IAU) has voiced many concerns about the risk to astronomy. We hope more clarity and solutions are found in days to come.