According to the Union of Concerned Scientists, a total of 1,381 satellites were still operational at the end of 2015. These satellites are mostly located in low Earth orbit (LEO) between 200 and 2,000 kilometers (124–1,242 miles) of altitude. LEO is home to 759 active satellites, or 55% of the total. This family of orbits remains the main orbital location of satellites due to the wide range of missions it allows and to the low energy required to reach it, which typically results in lower launch costs.
According to the Union of Concerned Scientists, a total of 1,235 satellites were active at the end of 2014. These satellites are mostly located in low Earth orbit (LEO) between 200 and 2,000 kilometers (124–1,242 miles) of altitude. LEO is home to 655 active satellites, or 53% of the total.
Satellites include a wide variety of systems performing an even wider range of missions from their different orbits. In 2014, launch operators attempted to place 296 spacecraft into orbit (including both satellites and other types of payloads), an increase of 38% from 215 spacecraft in 2013. The majority of spacecraft are launched to LEO—in 2014, this was the destination for 79% of all spacecraft, or 60% when excluding nanosatellites, which have masses of less than 10 kilograms (22 pounds).
There were 1,165 active satellites in orbit at the end of 2013, all performing various missions depending on their configuration and orbit. Of all active satellites, 437 (approximately 38% of the total) were in geosynchronous equatorial orbit (GEO), an orbit 35,790 kilometers (22,240 miles) above the Equator, which allows satellites to circle the Earth exactly once per day, thus appearing to be fixed above a single point on the Earth’s surface, which is valuable in communications applications.
In 2013, 193 satellites were successfully launched on behalf of 29 different countries. Of these, 101 were “microsatellites,” with a mass of less than 91 kilograms (200 pounds). These satellites often carry scientific payloads or serve as demonstrations of new technologies. They usually operate in LEO, have a short life cycle, and are launched together with a larger primary payload. In most cases, three to six microsatellites piggyback on the primary payload, although one Minotaur launch in November 2013 carried 29 such spacecraft, and a Dnepr launch two days later deployed 32 more.
Satellite teleports are permanent ground-based satellite uplink facilities. Teleports consist of several satellite dishes sited near a major terrestrial communications backbone, and they serve as the link between terrestrial communications infrastructure and in-orbit telecommunications satellites. According to WTA’s teleport industry report, a total of ## teleports were operated by commercial and broadcast companies worldwide as of 2010.
In 2012, 119 satellites were successfully launched on behalf of 24 different countries and international organizations. There were 1,050 active satellites in orbit at the end of 2012, according to the Union of Concerned Scientists. Of these, 435 satellites (approximately 41% of the total) were in GEO. An additional 504 satellites (48% of the total) operate in LEO, with most flying at an altitude of 600–900 kilometers (370–560 miles). Between these extremes is medium Earth orbit (MEO), in which there are 73 satellites (7% of the total). The 38 remaining satellites (4% of the total) are in highly elliptical orbits (HEO); the high and low altitudes of their orbits are quite far apart—sometimes tens of thousands of kilometers
The closer proximity to the Earth also greatly reduces signal delay from a LEO satellite to ground stations and allows for smaller receivers on the ground. While minimizing signal delay is not vital for DTH services or corporate networks, it makes the orbit ideal for voice traffic being sent directly to handheld devices. These lower orbits are challenging since the satellites constantly move in and out of view of individual ground receivers. If it is necessary to maintain a continuous link despite the movement of the satellites, a fleet of spacecraft is required to form a constellation.
Telecommunications technology has made the world a much more intimate place. This is in no small part due to satellites circling the globe providing communications, scientific research, broadcasting, navigation, imagery, and support for national defense efforts. The first satellite, Sputnik, was launched by the Soviet Union in 1957 and served to demonstrate that man-made objects can reach and maintain a simple orbit. This small craft with limited instrumentation did little more than measure the density of the upper atmosphere and provide information on how radio waves propagate through the ionosphere.