Satellite connectivity Skills: none IT concepts: geostationary, medium-Earth, and low-Earth orbit satellite characteristics, spectrum and licensing, satellite technology progress, important Internet-service satellite projects and some of their implications This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.

Where does this topic fit? Internet concepts Applications Technology (communication) Implications Internet skills Application development Content creation (images)

Low-Earth, medium Earth and geostationary satellite characteristics Altitude (miles) Latency (milliseconds) Orbit time (hours) LEO < 1,200 20-25 Around 2 MEO 1,200-22,236 110-130 Around 12 GSO 22,236 250-280 24 Orbit characteristics calculator Why is the geostationary satellite altitude exactly 22,236 miles while LEO and MEO are ranges? Where would the moon fit in this picture?

Footprint of a proposed SpaceX Starlink satellite Starlink is the trade name of SpacX’s proposed Internet-service satellite constellation. All things being equal, will LEO, MEO or GSO satellites have the largest footprint?

Footprint example – LEO and VLEO The signal is strongest when the satellite is directly overhead and fades as it moves away. When it gets too weak, the ground terminal automatically switches to another satellite with a better signal. Where would the strongest signal would be within the footprint?

Geostationary orbit (GSO) 35,786 km (22,236 mi) and directly above the equator Video broadcast and slow Internet The satellite remains over the same point on the Earth since it rotates around the Earth exactly once per day. Animate

Medium Earth Orbit (MEO) 1,200 - 22,236 miles Global Positioning System and medium speed Internet A relatively small constellation can insure full coverage of the Earth with multiple visible satellites. This animation shows the orbits of the GPS satellites and the number that are visible above the central US at a given time. Animate Source

Low-Earth Orbit (LEO) Under 1,200 miles Earth imaging, science, fast Internet (?) To be sure the entire Earth is covered at all times, many more satellites are needed. This animation was prepared for Teledesic, which was formed in the 1990s, but failed because the technology was inadequate, Internet use was much less common and there was much less complementary terrestrial technology. Animate

Ku-band: 12 to 18 gigahertz GHz Ka-band: 26.5 to 40 GHz Spectrum Ku-band: 12 to 18 gigahertz GHz Ka-band: 26.5 to 40 GHz V-band: 40 to 75 GHz E-band: 60 to 90 GHz Good news – higher frequency means faster transmission Good news – higher frequency means smaller antennas Bad news – higher frequency means more power or less distance Best news – you only have to know the previous good/bad news, not the frequency bands These statements are true given that other things remain equal. For example, more efficient

Licensed versus unlicensed spectrum Each country controls its own spectrum and the International Telecommunication Union tries to keep it uniform. The ITU is a UN agency. Did you apply to the FCC for a WiFi license? It WiFi is license-free. WiFi is in the 2.4 and 5 GHz bands. Do WiFi radios uses licensed or unlicensed spectrum?

Address the “digital divide” Do all Internet users have the same quality of service? Is there a digital divide within the United States? If successful, LEO will have many applications – the big one is to bring the Internet to unserved people. Source

Fewer, faster hops than fiber on long routes Another hoped-for advantage Los Angeles to Punta Arena, Chile Source

Teledesic failed in the late 1990s, what has changed?

In 1945, Arthur C. Clarke proposed geostationary satellite communication (The vision) “Fig. 2. Typical extra-terrestrial relay services. Transmission from A being relayed to point B and area C; transmission from D being relayed to whole hemisphere.” http://lakdiva.org/clarke/1945ww/ Extra Terrestrial Relays, Arthur C. Clark, Wireless World, October 1945, pages 305-308. Clark is best known as a science fiction author. Check out the article on 2001 a Space Odyssey. Arthur C. Clark also wrote 2001 a Space Odyssey

Technology progress – ground station equipment The “dish” on the left could only establish a link to a satellite and it had to be precisely pointed at a geostationary satellite and transmission and latency were very slow. Today’s “terminal” includes the antenna and a fast computer for switching between satellites as they move and interfaces for the Internet, mobile phone network and Wifi. It will be simple for a user to install. Early geostationary satellite dish in rural India Proposed low-Earth orbit satellite terminal with solar panels

Technology progress – communication Beam forming High speed Laser between satellites

Technology progress – rocketry Reusability Payload increases Milestones Founded; 2002 First Falcon 1 demo flight; 2006 First Falcon 1 flight to orbit: 2008 … First Falcon Heavy flight to orbit: 2018 First BFR flight to orbit: 2022 (est) Payload to LEO (https://en.wikipedia.org/wiki/Comparison_of_orbital_launch_systems) Falcon 1: 470 kg (expendable) Falcon 9: 13,150 kg Falcon Heavy : 33,800 kg BFR: 150,000 kg Reuability of booster, second stage and fairing Falcon 1: Expendable Falcon 9: Partial reuse Falcon Heave: Partial reuse BFR: Full reuse Elon Musk says they would have gone bankrupt had the 2008 Falcon 1 flight failed – it was their fourth attempt.

SpaceX Starlink status Three leading contenders four markets: Cloud service provider, mobile operators, air and sea, civil/government O3b mpower press conference: https://www.facebook.com/SES.Satellites/videos/1684713954894111/ OneWeb status SpaceX Starlink status O3b status

LEO optimism

Summary We have seen three types of satellite orbit – LEO, MEO and GEO – along with their characteristics, reviewed the technical progress that has made constellations of LEO and MEO Internet-service constellations possible and considered a few implications of their availability,

Track the progress of the Internet-service satellite projects here. Resources Track the progress of the Internet-service satellite projects here.

Self-study questions I mentioned three leading companies Which one(s) is/are pursuing the consumer market? Which one(s) is/are pursuing other markets? What are some non-consumer markets for satellite connectivity Which is best suited to the consumer Internet service market: LEO, MEO or GSO? Which has a larger footprint: LEO, MEO or GSO? Which has a longer latency time: LEO, MEO or GSO? What is latency a measure of?