Төмен салмақты және кішкентай спутниктік жүйелер

Satellites of low mass and size, usually under 500 kg

A small satellite, miniaturized satellite, or smallsat is a satellite of low mass and size, usually under While all such satellites can be referred to as "small", different classifications are used to categorize them based on mass. Satellites can be built small to reduce the large economic cost of launch vehicles and the costs associated with construction. Miniature satellites, especially in large numbers, may be more useful than fewer, larger ones for some purposes – for example, gathering of scientific data and radio relay. Technical challenges in the construction of small satellites may include the lack of sufficient power storage or of room for a propulsion system.

A number of commercial and military contractor companies are currently developing microsatellite launch vehicles to perform the increasingly targeted launch requirements of microsatellites. While microsatellites have been carried to space for many years as secondary payloads aboard larger launchers, the secondary payload paradigm does not provide the specificity required for many increasingly sophisticated small satellites that have unique orbital and launch timing requirements. In July 2012, Virgin Orbit announced LauncherOne, an orbital launch vehicle designed to launch "smallsat" primary payloads of into low Earth orbit, with launches projected to begin in 2016. Several commercial customers have already contracted for launches, including GeoOptics, Skybox Imaging, Spaceflight Industries, and Planetary Resources. Both Surrey Satellite Technology and Sierra Nevada Space Systems are developing satellite buses "optimized to the design of LauncherOne". Virgin Orbit has been working on the LauncherOne concept since late 2008, and , is making it a larger part of Virgin's core business plan as the Virgin human spaceflight program has experienced multiple delays and a fatal accident in 2014. In December 2012, DARPA announced that the Airborne Launch Assist Space Access program would provide the microsatellite rocket booster for the DARPA SeeMe program that intended to release a "constellation of 24 micro satellites (~ range) each with 1 m imaging resolution." The program was cancelled in December 2015. In April 2013, Garvey Spacecraft was awarded a contract to evolve their Prospector 18 suborbital launch vehicle technology into an orbital nanosat launch vehicle capable of delivering a payload into a orbit to an even more capable clustered "20/450 Nano/Micro Satellite Launch Vehicle" (NMSLV) capable of delivering payloads into circular orbits. The Swiss company Swiss Space Systems (S3) has announced plans in 2013 to develop a suborbital spaceplane named SOAR that would launch a microsat launch vehicle capable of putting a payload of up to into low Earth orbit. The Spanish company PLD Space born in 2011 with the objective of developing low cost launch vehicles called Miura 1 and Miura 5 with the capacity to place up to into orbit.

In the ten years of nanosat launches prior to 2014, only 75 nanosats were launched. One challenge of using nanosats has been the economic delivery of such small satellites to anywhere beyond low Earth orbit. By late 2014, proposals were being developed for larger spacecraft specifically designed to deliver swarms of nanosats to trajectories that are beyond Earth orbit for applications such as exploring distant asteroids.

The term "femtosatellite" or "femtosat" is usually applied to artificial satellites with a wet mass below Like picosatellites, some designs require a larger "mother" satellite for communication with ground controllers. Three prototype "chip satellites" were launched to the ISS on on its final mission in May 2011. They were attached to the ISS external platform Materials International Space Station Experiment (MISSE 8) for testing. In April 2014, the nanosatellite KickSat was launched aboard a Falcon 9 rocket with the intention of releasing 104 femtosatellite sized chipsats, or "Sprites". In the event, they were unable to complete the deployment on time due to a failure of an onboard clock and the deployment mechanism reentered the atmosphere on 14 May 2014, without having deployed any of the 5 gram femtosats. ThumbSat is another project intending to launch femtosatellites in the late 2010s. ThumbSat announced a launch agreement with CubeCat in 2017 to launch up to 1000 of the very small satellites. In March 2019, the CubeSat KickSat 2 deployed 105 femtosats called "ChipSats" into Earth orbit. Each of the ChipSats weighed 4 grams. The satellites were tested for 3 days, and they then reentered the atmosphere and burned up.

Small satellites usually require innovative propulsion, attitude control, communication and computation systems. Larger satellites usually use monopropellants or bipropellant combustion systems for propulsion and attitude control; these systems are complex and require a minimal amount of volume to surface area to dissipate heat. These systems may be used on larger small satellites, while other micro/nanosats have to use electric propulsion, compressed gas, vaporizable liquids such as butane or carbon dioxide or other innovative propulsion systems that are simple, cheap and scalable. Small satellites can use conventional radio systems in UHF, VHF, S band and X band, although often miniaturized using more up to date technology as compared to larger satellites. Tiny satellites such as nanosats and small microsats may lack the power supply or mass for large conventional radio transponders, and various miniaturized or innovative communications systems have been proposed, such as laser receivers, antenna arrays and satellite to satellite communication networks. Few of these have been demonstrated in practice. Electronics need to be rigorously tested and modified to be "space hardened" or resistant to the outer space environment (vacuum, microgravity, thermal extremes, and radiation exposure). Miniaturized satellites allow for the opportunity to test new hardware with reduced expense in testing. Furthermore, since the overall cost risk in the mission is much lower, more up to date but less space proven technology can be incorporated into micro and nanosats than can be used in much larger, more expensive missions with less appetite for risk.

Small satellites are difficult to track with ground based radar, so it is difficult to predict if they will collide with other satellites or human occupied spacecraft. The U. S. Federal Communications Commission has rejected at least one small satellite launch request on these safety grounds.