Feb 22 2021
Kacific1: The Advantages of Geostationary Orbit
On 16 December 2019, Kacific launched its first Ka-band HTS satellite, Kacific1, into geostationary orbit from Cape Canaveral, Florida, on a SpaceX Falcon 9 launch vehicle. The satellite became operational in early 2020.
But what is a geostationary orbit and what are the advantages of geostationary orbit? It’s a grand phenomenon of physics, and where most satellites reside. The geostationary orbit (GEO) is where the vast majority of communications and television satellites have been since Telstar first carried TV signals in 1965 and direct-to-home satellite TV started in the 1980s.
In 1945, British science-fiction writer Arthur C. Clarke showed in the October 1945 issue of the Wireless World magazine that if a satellite is in a circular orbit 35,786 kilometres above the Earth’s surface(a radius of 42164km when you add the radius of the earth), in the plane of the equator, and travelling at 11,070 kilometres/hour in the same direction as the rotation of the earth, then it appears to us to be stationary (the “Geostationary” orbit). You have to move fast to stand still, apparently! A little bit faster, or further from Earth and centrifugal forces would take the satellite into an elliptical graveyard orbit and eventually into outer space. Too close or too slow and gravity will eventually pull it back to earth.
That eventuality is a problem; dead satellites and stray parts continue for many years to rotate at the same speed in the same orbit. NASA reports that more than 21,000 parts larger than 10 cm are known to exist, and 500,000 between 1 and 10 cm. All the satellites and debris are travelling in the same direction and the same speed, so destructive impacts that we see in movies are extremely rare.
The speed and distance of a satellite in the geostationary orbit apply whatever the mass of the satellite, even to a 1-centimetre fragment weighing a gram. Kacific1 is a Boeing (Hughes) type BSS-702 with a launch mass of 6.8 tonnes (the gross weight of a big six-wheel truck) but it still just stays there year after year, with occasional tweaks from Kacific Satellite Operations Control. Its orbital position is 150°East in the geostationary arc; that’s almost overhead Massau Island, Papua New Guinea. From there Kacific1 can provide its broadband internet services from Nepal right into the middle of the Pacific and New Zealand.
Geostationary advantages satellite in Geostationary Earth Orbit appears to be in a fixed location to someone on Earth, so the reception antenna does not have to track its movement. The is perfect for high-speed internet connection because:
- A single satellite in the geostationary orbit can cover distances as large as whole oceans or continents, about one-third of the earth, meaning that three satellites in a system can cover the whole earth(except the polar regions).
- This wide area coverage makes high-speed Internet access from remote locations quick and easy.
- The satellite remains in the same relative position throughout the day, so antennas do not have to move, therefore; the reception dish does not require tracking so it’s simple and affordable
- The fixed position of the satellite gives a more stable bandwidth and internet connection. In Kacific’s case, the satellite’s performance is enhanced by
- Spot beams provide extra power(better service) in the areas where the users are; this gives reduced bandwidth cost.
- The necessary technical features making Kacific less subject to rain-fade than MEO and LEO satellites. The Geostationary disadvantage: latency. A minor disadvantage of the geostationary orbit is the distance from earth and “latency”, the extra milliseconds it takes for signals to get there and back. At the speed of light is takes a quarter of a second, more precisely .2387 of a second or 238.7 milliseconds. This makes no difference to our consumption of TV, YouTube, email and social media. In fact, your office and home internet have delays of the same order due to server response time at your ISP and international trunking and coordination in the packet switching with traffic from other users. Latency might be critical for financial market trading, but then they would be using dedicated connections other than on a satellite. But satellites have latency issues whichever orbit they are in. For example, a Middle Earth Orbit satellite at 20,200 km from the earth needs 134.8 milliseconds for data to get there and back. Global Positioning by satellite, which is in this orbit, has to allow for latency by building the distance of the triangulating satellites from the GPS receiver into the instantaneous calculations and by using synchronised atomic clocks. Why does Kacific not use MEO or LEO?LEO (Low Earth Orbit) and MEO (Middle Earth Orbit)are not ideal for getting broadband to underserved communities: •LEO and MEO require a constellation of multiple satellites, covering the entire planet, so the cost is higher.
- LEO and MEO satellites do not remain stationary relative to the earth, so they need complicated handover between satellites, which requires sophisticated and expensive tracking terminals. LEO needs even higher-speed tracking systems. As a result, bandwidth from LEO and MEO is more expensive.
- LEO and MEO can be subject to poor reception when deployed in rugged terrain due to the varying view angle with the satellite. However, LEO and MEO are suited to certain applications:
- LEO satellites are suited for some military applications, imagery and manned spacecraft like the ISS at 150 to 1000 km above the earth. (Airliners fly about 10kms above the earth.)
Do satellites fall out of the sky? No, they don’t “fall”. At the end of a satellite’s life, the operator can command it to slow down, whereupon it drops out of its orbit. Some are boosted into outer space. Most de-commissioned satellites burn up as they enter the earth’s atmosphere. In some cases, a few parts can get through and land on earth, so the operator’s Plan B must be to bring them down, if they survive re-entry, over the far oceans or uninhabited land-mass.
On July 11, 1979, Skylab returned to Earth, burning up over the Indian Ocean and Western Australia. Some large chunks survived re-entry, making landfall southeast of Perth and elsewhere. Nobody was hurt, but the Australian town of Esperance charged NASA $400 for littering. The media report from time-to-time on satellite re-entries. The 6.5-ton UARS climate satellite, launched in September 1991, studied Earth’s atmosphere for 14 years, was decommissioned by NASA in December 2005 and fell to Earth (with no reported damage) in September 2011. The European Space Agency’s GOCE satellite fell to Earth on Nov. 10, 2013, but met a fiery doom during re-entry as with China’s Tiangong space station on Oct. 13, 2019. An operational satellite has never fallen out of orbit by accident and they remain working and stable for 15 to 25 years.
Kacific –the Heart of Broadband
Kacific is delivering high-speed two-way internet to thousands of telcos, ISPs, other networks, and the end-consumers that they connect. The Kacific1 satellite is stable and happy in geostationary orbit and will be serving us all for 15 years or more.