In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as Earth's Moon.
A geostationary orbit, often referred to as a geosynchronous equatorial orbit (GEO), is a circular geosynchronous orbit 35,786 km (22,236 mi) above Earth's equator and following the direction of Earth's rotation. An object in such an orbit appears motionless, at a fixed position in the sky, to ground observers. Communications satellites and weather satellites are often placed in geostationary orbits, so that the satellite antennae that communicate with them do not have to rotate to track them, but can be pointed permanently at the position in the sky where the satellites are located. Using this characteristic, ocean-color monitoring satellites with visible and near-infrared light sensors can also be operated in geostationary orbit in order to monitor sensitive changes of ocean environments.
A Low Earth Orbit (LEO) is an Earth-centered orbit with an altitude of 2,000 km (1,200 mi) or less, or with at least 11.25 periods per day and an eccentricity less than 0.25. Most of the manmade objects in space are in LEO. A histogram of the mean motion of the cataloged objects shows that the number of objects drops significantly beyond 11.25.
A natural satellite or moon is, in the most common usage, an astronomical body that orbits a planet or minor planet.
Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object.
Anti-satellite weapons (ASAT) are space weapons designed to incapacitate or destroy satellites for strategic military purposes. Several nations possess operational ASAT systems. Although no ASAT system has yet been utilised in warfare, a few nations have shot down their own satellites to demonstrate their ASAT capabilities in a show of force. Only the United States, Russia, China, and India have demonstrated this capability successfully.
A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. As of February 2019, there are 352 minor planets known or suspected to have moons. Discoveries of minor-planet moons are important because the determination of their orbits provides estimates on the mass and density of the primary, allowing insights of their physical properties that is generally not otherwise possible.
Initially, the term space debris referred to the natural debris found in the solar system: asteroids, comets, and meteoroids. However, with the 1979 beginning of the NASA Orbital Debris Program, the term also refers to the debris from the mass of defunct, artificially created objects in space, especially Earth orbit. These include old satellites and spent rocket stages, as well as the fragments from their disintegration and collisions.
A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited on each revolution. It therefore has an inclination of 90 degrees to the body's equator. A satellite in a polar orbit will pass over the equator at a different longitude on each of its orbits.
A geocentric orbit or Earth orbit involves any object orbiting Planet Earth, such as the Moon or artificial satellites. In 1997 NASA estimated there were approximately 2,465 artificial satellite payloads orbiting the Earth and 6,216 pieces of space debris as tracked by the Goddard Space Flight Center. Over 16,291 previously launched objects have decayed into the Earth's atmosphere.
The Indian Space Research Organisation is the space agency of the Government of India headquartered in the city of Bengaluru. Its vision is to "harness space technology for national development while pursuing space science research and planetary exploration." Indian National Committee for Space Research (INCOSPAR) was established by Jawaharlal Nehru, the first Prime Minister of the Indian Government under the DAE in 1962, with the urging of scientist Vikram Sarabhai recognizing the need in space research. INCOSPAR grew into ISRO in 1969 also under the DAE. In 1972 Government of India setup a Space Commission and the Department of Space (DOS), bringing ISRO under the DOS. The establishment of ISRO thus institutionalized space research activities in India. It is managed by the Department of Space, which reports to the Prime Minister of India.
The Kessler syndrome, proposed by the NASA scientist Donald J. Kessler in 1978, is a scenario in which the density of objects in low Earth orbit (LEO) is high enough that collisions between objects could cause a cascade where each collision generates space debris that increases the likelihood of further collisions. One implication is that the distribution of debris in orbit could render space activities and the use of satellites in specific orbital ranges impractical for many generations.
The Orbiting Carbon Observatory (OCO) is a NASA satellite mission intended to provide global space-based observations of atmospheric carbon dioxide. The original spacecraft was lost in a launch failure on 24 February 2009, when the payload fairing of the Taurus rocket which was carrying it failed to separate during ascent. The added mass of the fairing prevented the satellite from reaching orbit. It subsequently re-entered the atmosphere and crashed into the Indian Ocean near Antarctica. The replacement satellite, Orbiting Carbon Observatory 2, was launched 2 July 2014 aboard a Delta II rocket. The Orbiting Carbon Observatory 3, a stand-alone payload built from the spare OCO-2 flight instrument, will be installed on the International Space Station's Kibō Exposed Facility in April 2019.
RazakSAT is a Malaysian Earth observation satellite carrying a high-resolution camera. It was launched into low Earth orbit on 14 July 2009. It was placed into a near-equatorial orbit that presents many imaging opportunities for the equatorial region. It weighs over three times a much as TiungSAT-1 and carries a high resolution Earth observation camera. Developed in conjunction with Satrec Initiative, the satellite's low inclination orbit brought it over Malaysia a dozen or more times per day. This was intended to provide greatly increased coverage of Malaysia, compared to most other Earth observation satellites. An audit report released in October 2011 revealed that the satellite had failed after only 1 year of operation.
A geosynchronous satellite is a satellite in geosynchronous orbit, with an orbital period the same as the Earth's rotation period. Such a satellite returns to the same position in the sky after each sidereal day, and over the course of a day traces out a path in the sky that is typically some form of analemma. A special case of geosynchronous satellite is the geostationary satellite, which has a geostationary orbit – a circular geosynchronous orbit directly above the Earth's equator. Another type of geosynchronous orbit used by satellites is the Tundra elliptical orbit.
Several Asian countries have space programs and are actively competing to achieve scientific and technological advancements in space, a situation sometimes referred to as the Asian space race in the popular media as a reference to the earlier Space Race between the United States and the Soviet Union. Like the previous space race, issues involved in the current push to space include national security, which has spurred many countries to send artificial satellites as well as humans into Earth orbit and beyond. A number of Asian countries are seen as contenders in the ongoing race to be the pre-eminent power in space.
The Iridium satellite constellation provides L-band voice and data coverage to satellite phones, pagers and integrated transceivers over the entire Earth surface. Iridium Communications owns and operates the constellation, additionally selling equipment and access to its services. It was originally conceived by Bary Bertiger, Raymond J. Leopold and Ken Peterson in late 1987 and then developed by Motorola on a fixed-price contract from July 29, 1993 to November 1, 1998, when the system became operational and commercially available.
Palapa-D, also known as Palapa D1, is an Indonesian geostationary communications satellite which is operated by Indosat Ooredoo. It was built by Thales Alenia Space, based on the Spacebus-4000B3 satellite bus, and carries 35 G/H band and 5 J band transponders. It is positioned in geostationary orbit at a longitude of 113° East, where it will replace the Palapa C2 satellite.
Kosmos 163, also known as DS-U2-MP No.2, was a Soviet satellite which was launched in 1967 as part of the Dnepropetrovsk Sputnik programme. It was a 280-kilogram (620 lb) spacecraft, which was built by the Yuzhnoye Design Bureau, and was used to investigate micrometeoroids and particles of dust in space.
