Satellite

• 1. Introduction

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  On the 4th of October 1957, the Soviet Union launched Sputnik 1, the first artificial satellite to reach Earth's orbit. The unexpected announcement of its success set off the Sputnik crisis in the United States and lit the fuse on the Space Race within the Cold War. A satellite is an object, usually a spacecraft, placed into orbit around a celestial body. As of the 28th of June 2025, there are 12,952 satellites in Earth's orbit. Of those, 8,530 belong to the United States, 1,559 to Russia, and 908 to China. How did a single Soviet sphere multiply into a swarm of nearly thirteen thousand machines? What keeps them aloft, what work do they do, and what happens when their working lives end? The answers reach from a thought experiment by Isaac Newton to a wooden satellite prototype called LingoSat.

• 2. Imagining The Orbit

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  Isaac Newton published the first mathematical study of an artificial satellite in his Philosophiae Naturalis Principia Mathematica in 1687. His thought experiment, known as Newton's cannonball, was meant to explain the motion of natural satellites. Fiction reached orbit before rockets did. Edward Everett Hale wrote the first fictional depiction of a satellite being launched, a short story titled The Brick Moon, in 1869, and the idea surfaced again in Jules Verne's The Begum's Fortune in 1879. Konstantin Tsiolkovsky, who lived from 1857 to 1935, published Exploring Space Using Jet Propulsion Devices in 1903, the first academic treatise on using rocketry to launch spacecraft. He calculated the orbital speed required for a minimal orbit and reasoned that a multi-stage rocket fueled by liquid propellants could reach it. Herman Potocnik explored orbiting spacecraft for peaceful and military observation in his 1928 book, The Problem of Space Travel, and described geostationary satellites that Tsiolkovsky had first put forward. In a 1945 Wireless World article, the English science fiction writer Arthur C. Clarke described communications satellites in detail and suggested that three geostationary satellites could cover the entire planet. The United States Air Force's Project RAND captured the stakes in May 1946, calling a satellite vehicle one of the most potent scientific tools of the twentieth century.

• 3. The Race To Launch

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  Sputnik 1 did more than circle the Earth. It helped identify the density of high atmospheric layers by the way its orbit changed, and it provided data on radio-signal distribution in the ionosphere. The chief designer behind it was Sergei Korolev, working under the Sputnik program. Political timelines collided in the mid-1950s. The White House announced on the 29th of July 1955 that the United States intended to launch satellites by the spring of 1958, an effort that became Project Vanguard, and two days later the Soviet Union announced its own plan to launch by the fall of 1957. Sputnik 2 carried the first living passenger into orbit on the 3rd of November 1957, a dog named Laika, sent without any possibility of return. The United States answered on the 31st of January 1958 with Explorer 1, its first artificial satellite, whose radiation detector led to the discovery of the Earth's Van Allen radiation belts. Weather watching from space began with the TIROS-1 spacecraft, launched on the 1st of April 1960 as part of NASA's Television Infrared Observation Satellite program, which sent back the first television footage of weather patterns taken from space. Other nations followed but often leaned on borrowed rockets. France broke that pattern on the 26th of November 1965, when the Asterix satellite reached orbit aboard a Diamant A rocket launched from Hammaguir in Algeria, making France the sixth country to have an artificial satellite.

• 4. Staying Aloft

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  Spaceships become satellites by accelerating or decelerating to reach orbital velocities, settling into an orbit high enough to avoid orbital decay from atmospheric drag and above their Roche limit. As of 2018, about 90% of the satellites orbiting Earth sit in either low Earth orbit or geostationary orbit, where a satellite stays still in the sky relative to a fixed point on the ground. Some imaging satellites choose a Sun-synchronous orbit so they can scan the entire globe under similar lighting. Most satellites use chemical or ion propulsion to adjust their orbit, paired with reaction wheels that control their three axes of rotation. Chemical thrusters usually burn hydrazine-based monopropellants or monomethylhydrazine and dinitrogen tetroxide bipropellants, which are hypergolic, meaning they combust spontaneously on contact. Ion thrusters on satellites are usually Hall-effect thrusters, which accelerate positive ions through a negatively charged grid. Ion propulsion is more efficient with propellant but produces very small thrust, around 0.5 newtons, so it requires a longer burn. These thrusters usually use xenon because it is inert, easily ionized, has a high atomic mass, and stores as a high-pressure liquid. Power comes mostly from solar panels, attached by slip rings that rotate to face the sunlight, while a few craft in deep space rely on radioisotope thermoelectric generators. Every solar-powered satellite also carries batteries, most commonly lithium-ion, because sunlight is blocked inside the launch vehicle and at night.

• 5. Eyes And Signals

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  Earth observation satellites gather information for reconnaissance, mapping, and monitoring of weather, ocean, and forest. As of 2021, there are over 950 such satellites, with the largest number operated by Planet Labs. Weather satellites track clouds, city lights, fires, the effects of pollution, auroras, sand and dust storms, snow cover, and the boundaries of ocean currents. Drought can be monitored by comparing the current vegetation state to its long-term average, and anthropogenic emissions can be tracked by evaluating tropospheric nitrogen dioxide and sulfur dioxide. When an observation or communications satellite is deployed for military or intelligence purposes, it becomes a spy or reconnaissance satellite, used for early missile warning, nuclear explosion detection, electronic reconnaissance, and radar imaging surveillance. Navigational satellites transmit radio time signals so that mobile receivers on the ground can fix their location, and the clear line of sight combined with improving electronics allows accuracy on the order of a few meters in real time. Communications satellites act as radio relay stations in orbit, each carrying dozens of transponders with a bandwidth of tens of megahertz. To save cost and effort, many satellites use a standardized bus, the most popular being small CubeSats, and similar satellites can work together as constellations. The first standardized satellite bus was the HS-333 geosynchronous communication satellite, launched in 1972.

• 6. Crowded And Dirty Skies

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  Aluminium typically makes up around 40% of a satellite's mass, valued for being lightweight and cheap, yet it is one of the most carbon-intensive metals to mine and refine. Satellite manufacturing also draws on rare elements such as lithium, gold, and gallium, some in limited supply. Launch vehicles demand far more raw material, and their booster stages are usually dropped into the ocean and not recovered; two empty boosters from Ariane 5, made mainly of steel, weighed around 38 tons each. Rocket launches release black carbon, carbon dioxide, nitrogen oxides, aluminium, and water vapour into every layer of the atmosphere. The greenhouse gases from rockets are considered trivial, contributing around 0.01%, compared with the aviation industry, which accounts for 2-3% of total global greenhouse gas emissions. The greater worry sits higher up, in the stratosphere, where radicals such as nitrogen oxides, hydrogen oxides, and chlorine oxides can deplete ozone in trace amounts, though launch rates would need to increase tenfold to match regulated ozone-depleting substances. The sky itself is changing. The overall diffuse brightness of the night skies is estimated to have risen by up to 10% above natural levels, which may confuse insects and night-migrating birds that navigate by celestial patterns. Some craft leave more dangerous legacies; Kosmos 954, Kosmos 1402, and the Transit 5-BN-3 dispersed radioactive materials when they came down.

• 7. Endings And Aftermath

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  Physical collection or removal of dead satellites is not economical or even currently possible. When satellites reach the end of life in a controlled manner, they are intentionally deorbited or pushed to a graveyard orbit farther from Earth, but that orbit holds them for hundreds of years and only delays the problem of space debris. After the late 2010s, as large satellite internet constellations more than doubled the number of active on-orbit satellites within five years, companies began proposing regular planned deorbiting of older satellites as part of obtaining a launch license. SpaceX Starlink satellites, the first large internet constellation to exceed 1000 active satellites on orbit in 2020, are designed to be fully demisable and burn up completely on reentry. Yet reentry introduces more material and pollutants into the atmosphere, raising concerns about damage to the ozone layer and a possible accidental geoengineering of the climate, and roughly 70% of deorbited satellites end up in the ocean and are rarely recovered. Space debris can drive a Kessler syndrome that could curtail future space endeavors, while the astronomical community, including the IAU, reports that orbital pollution from constellations like Starlink is rising significantly. Wood has been proposed as an alternative material to cut pollution and debris. Japan's space agency, JAXA, and NASA plan to send a wooden satellite prototype called LingoSat into orbit in the summer of 2024, having sent the first wood samples into space in 2021 to test the material's resilience.