A satellite is basically any object that revolves (or in other words, route ways) around another object in space. Some satellites are congenital, while others are artificial ( man- made). The moon is an illustration of a natural satellite that orbits the world. within the system, there are six planetary satellite systems containing 185 given natural satellites. 

now, the stint satellite usually refers to man-made objects flown in space. very similar to their natural counterparts, these orbit a planet and therefore the key difference is that they need been intentionally placed into orbit.

Sputnik 1 is that the world’s first satellite . it had been embarked on space on 4 October 1957 by the Soviet Union . Since then, about 8,900 satellites from quite 40 countries are launched.

It is important to notice here that satellites are used for several purposes. as an example , they will be wont to make star maps and maps of planetary surfaces, and also take pictures of planets they're embarked on .

Military and civilian earth observation satellites, communications satellites, navigation satellites, weather satellites, and space telescopes are some of the most common types.

Satellites are often computer-controlled semi-independent devices. Satellite subsystems are responsible for a variety of functions, including power generation, thermal control, telemetry, and attitude.

Satellites include space stations and human spaceships in orbit. Satellite orbits vary widely depending on the satellite's purpose, and are categorised along the way. Low earth orbit, polar orbit, and geosynchronous orbit are three well-known (overlapping) classes.

How are these satellites embarked on space?

this is often through with a launch vehicle, basically a rocket that places the satellite into orbit. More often than not, the rocket lifts faraway from a launch pad ashore but there are some that are launched stumped from a submarine or a mobile maritime platform, or aboard a plane.

In this blog, we shall take an in depth check out communications satellites. they're called so because they're used for communication purposes.

What is the definition of a communications satellite?

A satellite is a man-made satellite that uses a transponder to relay and amplify radio telecommunications signals. It basically establishes a link between a source transmitter and a receiver located at different points on the globe. Television, telephone, radio, internet, and military applications all use communications satellites.

There are currently 2,134 communications satellites within the earth’s orbit and these comprise both private and government organizations. Several are in geosynchronous orbit 22,236 miles (35,785 km) above the equator, in order that the satellite appears stationary at an equivalent point within the sky.

The orbital period of those satellites is that the same because the rotation rate of the world , which successively allows the satellite dish antennas of ground stations to be aimed permanently at that spot; they are doing not need to move along and track it. Since the high frequency radio waves used for telecommunications links pass by line of sight, they get obstructed by the curve of the world.

What these communications satellites do is that they relay the signal round the curve of the world thus making possible communication between widely removed geographical points. Communications satellites use a good range of radio and microwave frequencies. International organisations have regulations defining which frequency ranges (or bands) specific organisations are allowed to utilise to avoid signal interference. Signal interference is less likely as a result of this band assignment.

Satellite Orbits :

Satellites are often classified as per their orbits. As mentioned earlier, many are geostationary satellites, as they need a geosynchronous orbit (GEO), which is 22,236 miles (35,785 km) from the earth’s surface. Here the satellite appears to be within the same position within the sky when viewed by ground observers. So here ground antennas don't need to track the satellite across the sky.

Medium Earth Orbit (MEO) satellites are those that are closer to the earth; their orbital altitudes vary from 2,000 to 36,000 kilometres (1,200 to 22,400 mi) above the world . The region below medium orbits is around 160 to 2,000 kilometres (99 to 1,243 mi) above the world and is named Low Earth Orbit (LEO).

With MEO and LEO satellites orbiting the world faster, they're not continually visible within the sky at a hard and fast point on the world . Instead, they seem to cross the sky and “set” once they go behind the world . this suggests that offering continuous communications services with these lower orbit satellites would wish a much bigger number of satellites, thus ensuring that a minimum of one among them is usually within the sky to facilitate transmission of communication signals. But it's also important to notice that thanks to their relatively shorter distance to the world , their signals are much stronger.

Satellite Constellations

A constellation of satellites is a group of spacecraft that work together. The Iridium and Globalstar systems are two such constellations that are said to provide satellite phone services (mostly to rural places). There are 66 satellites in the Iridium system. Today, a low-earth-orbit satellite may provide discontinuous coverage by storing data received while travelling over one part of the earth and transmitting it later while flying over another section. A good example is the CASCADE system, which is being employed by Canada's CASSIOPE satellite.

Rise of Communication satellites : 

The Soviet Union launched Sputnik 1, the world's first artificial earth satellite, into orbit on October 4, 1957. It was equipped with an on-board radio transmitter that operated on two frequencies: 20.005 and 40.002 MHz at the time. Sputnik 1 was a significant step forward in space research and rocket development. It was not, however, deployed in orbit to relay data from one point on Earth to another. Pioneer 1, a planned lunar probe, was the primary satellite used to carry communications. The spacecraft travelled high enough to carry out a proof-of-concept telemetry relay around the globe, first from Cape Canaveral to Manchester, England, then from Hawaii to Cape Canaveral, and then across the earth from Hawaii to Manchester.

Applications/ Uses of Communications Satellites

1. Satellite phones:

They are the primary and historically most vital use of communications satellites. The fixed Public Switched Telephone Network carries telephone calls from landline phones to an earth station, from where they're transmitted to a geostationary satellite. The downlink follows a similar path. With significant improvements in submarine communications cables through the utilization of fiber-optics, satellites are not any longer getting used for fixed telephony on an equivalent scale. But that doesn’t mean that satellites are not any longer used for communication. foreign places like Ascension Island, Saint Helena, Diego Garcia, and Easter Island haven't any submarine cables in commission , so those areas need satellite telephones. Satellite communication is additionally needed in continents and countries where landline telecommunications are rare to nonexistent - say, in Antarctica, Greenland large regions of South America, Africa, Canada, China, Russia, and Australia. Other land use for satellite phones include ships stumped , rigs stumped , copy for hospitals, military and recreation. Typically, satellite phone systems function through an area phone system during a n isolated area with a link to the phonephone system in a main acreage .There also are services which will send a radio wave to a phone system . during this example, almost any sort of satellite are often used. Satellite phones reach out on to a constellation of either geostationary or low-earth-orbit satellites. Calls are subsequently routed to a satellite teleport that is linked to the wireless lan.

Satellite television

 It refers to the delivery of television programmes to viewers via a satellite orbiting the earth and relaying it to the viewer's location. The signals are received via a satellite dish, an outdoor parabolic antenna, and a low-noise block downconverter. A receiver - either an external set-top box, or a built-in television tuner - decodes the specified television programme for viewing on a television receiver . satellite TV offers a good range of channels and services. it's the sole television available in many remote areas that don't have terrestrial television or cable television service. Modern systems signals are passed on from a satellite on the Ku band frequencies (12–18 GHz) that require only alittle dish but a meter in diameter.Also unlike early systems that used analog signals, modern ones use digital signals which permit transmission of the fashionable television standard HDTV , because of the much improved spectral efficiency of digital broadcasting. As of 2018, the sole channels counting on satellite broadcasting in analog signals are Brazil’s Star One C2 and American channel C-SPAN on AMC-11. Different receivers are required for the 2 types.Unencrypted transmissions and channels are available for free-to-air or free-to-view. Other channels (pay television) use encryption and require viewers to subscribe and pay a monthly subscription to receive programmes.satellite television consumption now features a lot less takers thanks to the cord-cutting trend where people are preferring to observe internet based streaming television.

Satellite Radio:

A satellite radio or subscription radio (SR) is essentially a digital radio wave that's relayed by a satellite and this typically covers a wider geographical range than terrestrial radio signals. Satellite radio provides audio broadcast services in some countries, among them is that the US. Mobile services, like SiriusXM, and World space, let listeners travel across the continent and tune to an equivalent audio programming anywhere,Music Choice and Muzak's satellite-delivered material, for example, require a fixed-location receiver and a dish.altogether instances, the antenna should have a transparent view to the satellites. In places that have tall buildings, bridges, or maybe parking garages obscuring the signal, repeaters are often wont to make the signal available to listeners.

Amatuer Radio Satellite:

Amateur radio operators make use of amateur satellites, that are created specifically for amateur radio traffic. Most of those satellites function as space borne repeaters, and are generally employed by amateurs equipped with UHF or VHF radio equipment and highly directional antennas like Yagis or dish antennas. thanks to launch costs, most amateur satellites are embarked on low earth orbits, and are designed to affect only a couple of brief contacts at a given time.

Satellite internet :

Internet access via communications satellites is referred to as satellite Internet access.Today, consumer grade satellite Internet service is usually offered to people through geostationary satellites which will provide relatively high data speeds, especially because of newer satellites using Ku band to realize downstream data accelerates to 506 Mbt/s. After the 1990s, satellite communication technology has been used as a way to attach to the web using broadband data connections. this is often particularly useful for people in remote areas who cannot avail a broadband connection.

Satellites used for Military Purposes:

Communications satellites also are used for military communications applications, like Global Command and Control Systems. Military systems that use communication satellites are the MILSTAR, the DSCS, and therefore the FLTSATCOM of the us , NATO satellites, UK satellites (for example, Skynet), and satellites of the previous Soviet Union . GSAT-7, India's first military communication satellite, has transponders that operate in the UHF, F, C, and Ku bands. Military satellites usually operate within the UHF, SHF or EHF (also referred to as Ka band) frequency bands.

Satellite Communication Today :

Since the launch of the primary satellite Sputnik 1, around 8,900 satellites from quite 40 countries are launched. consistent with a 2018 estimate, 5,000 are in orbit. Out of those 5,000, 63% of operational satellites are in low-earth orbit, 6% are in medium-earth orbit (at 20,000 km), 29% are in geosynchronous orbit (at 36,000 km) and therefore the remaining 2% are in elliptic orbit. Some large space stations have actually been launched in parts and assembled in orbit. it's important to notice that out of the 5,000 satellites in orbit, only 1,900 were operational in 2018, while the remainder have now become space debris.Five satellite collisions have resulted in space debris as of December 2016.

Space debris is additionally referred to as space trash, space litter, space junk or orbital debris.Today, several steps are being taken to affect such debris. The U.S. features a set of ordinary practices for civilian (NASA) and military (DoD and USAF) orbital-debris mitigation, very similar to the ecu Space Agency. In 2007, the world organization for Standardization (ISO) began preparing a world standard for space-debris mitigation.

Germany and France have posted guarantees to protect property from harm caused by debris.Another approach to mess mitigation is designing the mission architecture so on always leave the rocket second-stage in an elliptical geocentric orbit with a low-perigee, thus ensuring rapid orbital Decomposition of used rocket bodies and avoidance of long-term orbital debrisExternal removal of space debris has not seen many takers primarily because it's been found to be not cost effective.

April 2018 saw the launch of the RemoveDEBRIS mission. Using mock targets in low earth orbit, this mission will test the effectiveness of multiple Active Debris Removal (ADR) systems.it'll do so by completing several planned experiments and therefore the platform is accordingly fitted with a net, a harpoon, a laser ranging instrument, a dragsail, and two CubeSats (miniature research satellites). RemoveDEBRIS was launched aboard the SpaceX Dragon refill spacecraft as a part of the CRS-14 mission and it received the International space platform (ISS) on April 4, 2018

Read more at : 

1 ) https://www.mindstick.com/news/920/astro-an-emerging-private-rocket-company