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A simple definition of a satellite is “satellite is an object that orbits a planet or a star.” We all know that Earth is a satellite as it orbits the sun and so is the Moon as it revolves around the Earth. Both Earth and Moon are natural satellites. But in the modern age, the word “satellite” is normally used for an object that is launched into space intentionally for a variety of reasons.
Artificial Satellites
If human intervention is involved in placing the machine(satellite) into orbit, it is an artificial satellite. Artificial satellites commonly move in a geostationary orbit. Satellites are fully autonomous. Once they are in the orbit, they rotate around the Earth, using sophisticated lenses and sensors to image the planet or the star and send data back to the ground station. Satellites make it easier and more efficient to plan the operations.
From Sputnik1 to SpaceX
“The Soviet Union was the first to launch a satellite into space. The satellite was launched in 1957 and was called Sputnik 1. The first satellite picture of Earth came from NASA's Explorer 6 in 1959.”1
The first international space station Salyut 1 was the first international space station, that was launched by the Soviet Union on April 19, 1971. This station was launched into low Earth orbit and hosted the crew of 3 cosmonauts for an unprecedented 24-days mission.
But sadly, this mission ended unpropitiously as the crew died due to the sudden depressurization of their Soyuz 11 spacecraft shortly before reentry into the Earth’s atmosphere. Over the ensuing decades, Russian engineers kept working on the original Salyut design. This journey led them towards launching more adept generations of space stations including the Salyut series, DOS, and Almaz programs.
Space X: The commercial space industry
SpaceX, founded by Elon Musk, is the first private space company that accomplished the monumental feat of launching and returning a spacecraft from Earth’s orbit. This company, then, started a series of setting historical landmarks in space exploration. Till now, it is the only private company capable of returning a spacecraft from low-Earth orbit. Moreover, it launched the first commercial spacecraft “Dragon spacecraft” to deliver cargo to and from the International Space Station. In 2020, SpaceX took humans to space as well.
Falcon 9 is the first reusable rocket which is also created by SpaceX. The mission in which Falcon 9 rocket was flown is known as Commercial Resupply Services 13 (CRS-13). It was launched from Cape Canaveral Air Force Station in Florida. It was the first time NASA approved such a mission and the fourth time SpaceX has launched with what it says is a “flight-proven” booster.
SpaceX's Falcon 9 booster launched the Crew-1 mission in November 2020 and it was brought to port after landing on a barge at sea. This booster has been reused for the Crew-2 mission; making it the first time the “same rocket booster” has been used for multiple human launches. That’s a history-making step taken by the combined effort of both SpaceX and NASA.
China’s First space station
China Manned Space Agency (CMSA) started to build a low Earth orbit space station in 2021. In May 2021, Tianhe, the first of the orbiting space station's three modules were launched by China, and the country aims to finish building the station by the end of 2022.
CMSA hopes to include three astronauts on Tiangong for at least a decade. Many experiments from China and other countries will be carried out on the space station.
Global Space Internet
The internet will soon change into the Global Space Internet. Elon Musk’s Starlink is going to provide a broader internet connection worldwide through a string of satellites. Currently, Starlink is available for testing in limited parts of the US, Canada, Mexico, New Zealand, Australia, the UK, and several other countries. Soon enough, maybe by the end of 2023, the service would be available worldwide.
Starlink is the first satellite internet service provider to use low Earth orbit, with all of its satellites orbiting between 540 and 1,150 kilometers above the Earth's surface. Such low-flying satellites can send data faster and with less latency (or lag time), thus, providing a better service. Other Global Space provider projects include Amazon Project Kuiper, OneWeb, and Telesat. They can give Starlink a hard competition in the future.
Types of Satellites
Satellites are launched into space to fulfill a specific role and on the basis of their role they are categorized into the following types:
1. Communication Satellite
Communication satellites receive signals sent their way from a ground terminal, amplify them and then transmit them back to another ground terminal. This space station is used for telecommunication, radio, and television signals.SCORE was the first communication satellite. It was launched on December 18, 1958.
2. Geocentric Orbit type Satellite- LEO, MEO, HEO
All the satellites having Earth as their center of revolution are geocentric satellites. Geocentric orbits are mostly classified based on altitude. The lowest altitude where a stable orbit can be created is 100 miles. This is called the low Earth orbit (LEO). All objects whose furthest distance from Earth while in a stable orbit ( apogee of the spacecraft) is greater than 2000 kilometers, but less than 35000 km are said to be in the MEO. A high Earth orbit(HEO) is a geocentric orbit with an altitude above 35,786 kilometers, 22,236 mi.
3. Geostationary Satellites (GEOs)
Geostationary satellites appear to be fixed over one spot above the equator synched with the orbit of the Earth. The position of the satellite is relative to earth antennas hence it does not need reorientation. It is best for meteorological applications because these satellites are positioned at a high altitude (35,786 kilometers).
4. Global Positioning System (GPS)
GPS informs you of your location on Earth. It is used for navigation, mapping, tracking, and timings. Ivan A. Getting, Roger L. Easton, and Bradford Parkinson invented GPS. The first prototype spacecraft was launched in 1978 and the full constellation of 24 satellites became operational in 1993. Global positioning system (GPS) is available Free of cost everywhere on Earth.
5. Ground Satellite
Satellite Ground Stations (SGS) are built for collecting and streaming remote sensing satellite data to a variety of users and applications. Such centres collect weather and other data to provide customers and the public with the required information. Satellite ground stations generally consist of the following main components: a reception antenna, a feed horn, waveguide, and receiver. All are typically mounted on a pedestal. Satellite Ground Stations can also be protected by a ‘radome’; the sphere used to cover the antenna.2
6. Nano-Satellites, CubeSats and SmallSats
The Nanosatellite Launch Adapter System (NLAS) was developed to increase access to space while simplifying the integration process of miniature satellites, called nanosats or CubeSats. CubeSats are a class of nanosatellites that use a standard size and form factor. Small spacecraft (SmallSats) focus on spacecraft with a mass of fewer than 180 kilograms. NASA Ames launched its first CubeSat, GeneSat, in December 2006. Since then Ames has launched 16 CubeSat spacecraft varying in size from 1U to 3U with an additional 12 CubeSats in development or awaiting launch.3
7. Navigation Satellite
It is used to trace the exact location of any object on Earth. It has led to the development of new applications, technology, and business uses.
8. Polar Satellite
A polar satellite passes above both poles of the body being orbited (planet or a star) on each revolution. It, therefore, has an inclination of almost 90 degrees to the equator. These satellites are used for mapping, earth observation, reconnaissance, as well as for weather forecasting.
9. Remote Sensing Satellite
Remote sensing satellites detect and monitor the physical characteristics of a geographical location by measuring its reflected and emitted radiation at a distance. Three types of orbits are typically used in remote sensing satellites, such as geostationary, equatorial, and sun-synchronous orbits.
Companies working on Satellites and other Space Technologies
A sample list of companies from satellites and space database that are engaged in Satellite technology, Space applications, Aerospace4 and Drones 5
1. Accion Systems Inc.
Accion Systems is developing affordable satellite propulsion technology for lightweight (under 200 kg) vehicles.
2. Air Force Office of Scientific Research (AFOSR)
AFOSR awards research grants and contracts for national defense to academic institutions and commercial firms.
3. Arianespace
Arianespace offers space transportation services for any type of commercial and institutional satellite into any orbit.
4. Asia-Pacific Satellite Comm Co (APSCC)
APSCC is a non-profit association representing the satellite and space-related industries worldwide.
5. ADS Group Limited
ADS is the trade organization for the UK’s aerospace, defense, security, and space industries.
6. AeroVironment
AeroVironment operates advanced Unmanned Aircraft Systems (UAS) and electric transportation solutions.
7. ALCORE Technologies
Alcore is an industrial company specializing in unmanned aerial surveillance vehicles less than 600 lbs (300 kg).
8. Association of Universities for Research in Astronomy (AURA)
AURA operates three centers: Optical-Infrared Astronomy Research Laboratory; Solar Observatory; and the Space Telescope Science Institute.
9. Canadian Space Agency (CSA)
CSA promotes the peaceful use and development of space to advance knowledge and the economic benefits for Canadians.
10. DroneUp
DroneUp provides end-to-end aerial solutions for data collection and delivery.
Conclusion
Scientists are working on satellites and continuing their research and experiments to develop even better technology in the future. For now, satellites have applications in areas such as Navigation, Reconnaissance, Space science, Climate & environmental monitoring, Communication, Weather forecasting and more, etc.
Footnotes
1 NASA Knows! (Grades K-4) series.
2 ESS Weathertech (ESS) is an advanced technology company specializing in solutions in environmental and allied fields such as meteorology, hydrology, oceanography, atmospheric, fire weather, and other specialized engineering fields, supplying to government, defense, research, institutional, aviation industries and the private sector.
3 What are SmallSats and CubeSats? | NASA
4 Aerospace; the branch of technology and industry concerned with both aviation and space flight.
5 In aviation and space, a drone refers to an unpiloted aircraft or spacecraft.
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