Rockets, satellites, and the services they provide, once the domain of governments, are increasingly launched and managed by privately owned companies. Until 1982, the U.S. government launched all civil and commercial payloads into orbit, and U.S. launch vehicle manufacturers produced vehicles only under contract to the National Aeronautics and Space Administration (NASA) or the Department of Defense (DOD). Most of the satellites they carried into orbit were owned by U.S. or foreign government agencies. Now, commercial payloads are generally launched by private providers, and the payloads themselves are increasingly likely to be owned by private entities: Of the 576 U.S.-owned satellites currently in orbit, 286 were launched for commercial reasons and another 12 on behalf of academic users. The growth of the commercial space sector is a result of a deliberate shift in federal policy. The Commercial Space Launch Act of 1984 states the following: [T]he United States should encourage private sector launches, reentries, and associated services and, only to the extent necessary, regulate those launches, reentries, and services to ensure compliance with international obligations of the United States and to protect the public health and safety, safety of property, and national security and foreign policy interests of the United States . That law was amended in 2004 to provide that "the regulatory standards governing human space flight ... evolve as the industry matures so that regulations neither stifle technology development nor expose crew or space flight participants to avoidable risks as the public comes to expect greater safety for crew and space flight participants from the industry." National security agencies have emphasized the importance of the commercial space industry, in particular the space industrial base. To foster its growth, the commercial space industry has purposely been insulated from some types of federal regulation often applied to other industries. For example, the Commercial Space Launch Act directs the Secretary of Transportation to issue regulations affecting the design and operation of launch vehicles only to protect the safety of crew, thereby giving launch vehicle manufacturers and operators wide leeway in developing new rockets. An initial eight-year "learning period" for this limited regulation has been twice extended, most recently until 2023. Global spending on space activity reached an estimated $323 billion in 2015. Of this amount, nearly 40% was generated by commercial space products and services and 37% by commercial infrastructure and support industries. The U.S. government—including military and national security agencies and NASA—accounted for about 14% of global spending, and government spending by other countries the remaining 10%. The commercial space industry has distinct subsectors. Most commercial payloads are placed in orbits around Earth by launch vehicles that have the thrust to escape Earth's gravity. Typically, the firms that provide commercial launch services also design and assemble the rockets they launch. The payloads, such as satellites and manned space capsules, are manufactured by other firms. Service providers (such as television broadcasters) may design and build their own satellites, or purchase them from third-party manufacturers. The ground stations that control and communicate with the payloads, which form an integral part of the spacecraft operations, may be operated by the launch services, the payload owners, or entirely separate entities. The satellite supply chain is global, with a small number of manufacturers. Satellites are custom-made for their users, using specialized parts, which require extensive testing to ensure they will operate in a space environment where replacement and repair are generally not options. Because there are a limited number of rocket launches each year, supply chain deadlines are governed by a satellite launch window; if that window is missed because of production or regulatory delays, it may be many months or even years before another launch vehicle will be available to carry the satellite into orbit. Minimizing the mass and physical dimensions of a satellite is critically important, because heavier or bigger satellites are likely to require larger, more costly launch rockets. Appendix A shows a range of existing satellites, their weight, and corresponding familiar objects that approximate the same mass. The United States is the largest manufacturer of spacecraft, followed by the European Union and Russia. The global commercial satellite manufacturing sector, with $6 billion in revenues in 2015, attempted 86 launches carrying 262 spacecraft. Of these, 126 were satellites weighing less than 22 pounds (10 kilograms). The growing use of these smaller satellites has led to a doubling in the number of satellites launched. However, smaller satellites comprise a tiny portion of the mass of vehicles sent into space: Of 392 tons of satellites launched in 2015, the total weight of satellites under 22 pounds was barely half a ton. Regardless of their size and type, satellites generally utilize similar types of components and instruments ( Figure 1 ), including the following: S olar panels generate electricity that is stored in onboard rechargeable batteries . A propulsion tank adjusts altitude and orbit control and assists in placing the satellite into final orbit; several thrusters assist with these maneuvers and may be used later to move the satellite into a new orbit or, when the satellite's useful life is over, into a "graveyard" orbit farther away from Earth. T hermal control is the skin that prevents damage to the internal components in the extreme temperatures of space. Satellites pass through a wide range of temperatures, ranging from about -300°F to +200°F. Certain components, such as batteries, have an optimum operational range of about +50°F to +85°F. The skin is composed of a multilayer thermal blanket made of lightweight reflective films. In addition, a coated or mirrored optical solar reflector may be used, which acts like a radiator to keep the components from overheating due to solar energy and radiation. An electronics system controls satellite functions, such as flight operations, the direction in which the satellite points, and mathematical analysis. A communications system includes a transmitter, a receiver, antenna e that send data to and receive instructions from ground stations, and an amplifier that produces high-power radio frequency signals. Specialized components are determined by the core mission of the satellite. For example, a remote sensing satellite might include an image sensor, a telescope, and a digital camera. Satellites are placed into different types of Earth orbits depending on their planned use: low Earth orbit, medium Earth orbit, geosynchronous Earth orbit, and high Earth orbit ( Figure 2 ). The altitude of the orbit determines how frequently the spacecraft orbits the Earth. Some types of space activities require closer proximity to Earth for supply and maintenance and to provide higher-resolution images of Earth. Others operate farther in space to more effectively deploy their services. The International Space Station (ISS), for example, is in low Earth orbit, taking 90 minutes for a full orbit, while a television or weather satellite in geosynchronous orbit will take a full day. A satellite in geosynchronous orbit matches the Earth's rotational speed, so unlike other types of satellites, it will remain in the same place above the Earth and can therefore provide the same locations with weather monitoring or telecommunications. At the end of June 2016, 1,419 satellites were in operation, with 55% in low Earth orbit, 36% in geosynchronous orbit, 7% in middle Earth orbit, and the remainder in high Earth orbit. Of these, 576 are U.S. satellites, 140 Russian, 181 Chinese, and 522 from other countries. Of the U.S. satellites, 286 are commercial, 146 military, 132 government, and 12 civil. The commercial launch industry booked $2.6 billion in revenues in 2015, when it attempted 86 rocket launches. Of these, 83 launches successfully placed payloads into orbit. Twenty-two launches carried commercial satellites and 64 carried government payloads; some carried both. It has been estimated that total costs of global launches for commercial, civil, and military purposes (including servicing the ISS) in 2015 were about $8 billion. The U.S. Government Accountability Office (GAO) identified three factors spurring the growth of the U.S. launch industry: the NASA commercial cargo program and other federal contracts; aggressive pricing by SpaceX and some other private providers, which are "more price competitive compared with foreign launch providers"; and the emerging space tourism and small satellite industries. A traditional spaceport was a facility owned by the federal government, such as Kennedy Space Center and Cape Canaveral Air Force Station (both in Florida) and Vandenberg Air Force Base (in California). The federal government has used these facilities for its own launches and also promoted their use for commercial space access. Several private providers of launch services have chosen to build their own facilities. The Federal Aviation Administration (FAA) has licensed 10 spaceports in seven states: California, Florida, Texas, Oklahoma, Alaska, Virginia, and New Mexico. California, Florida, and Texas each have two licensed spaceports. Additional launch sites have been proposed in other states. Spaceports are configured for specific uses. Some are planned only to launch large vertical rockets, while others hope to lure space tourism with facilities for winged launch vehicles. Regardless of the type of launch vehicles using the sites, they have common infrastructure needs, including access for delivery of large launch vehicle components; room to assemble rocket parts into a launch vehicle; facilities for receiving and storing propellants and loading them aboard rockets; secure facilities for storing cargo, payloads, and scientific experiments; work space for crews, engineers, and launch personnel; and meteorological equipment to monitor weather patterns prior to scheduled launches. The ISS also increasingly offers certain types of launch services; part of it is designated as a national laboratory, a shared resource for NASA and private industry; astronauts have used its robotic arm to launch small satellites into orbit, many of them only 4-inch cubes. In 2015, 42 small satellites, primarily with commercial functions, were launched as cargo to the ISS for later deployment into individual orbits. U.S. crew members and cargo were transported to the ISS in NASA's Space Shuttle from 2000 until 2011, when the shuttle was retired.