Nanosatellites, also called "nanosats", are a relatively recent term used to describe artificial satellites with a mass between 1 and 10 kg (2.2–22 lb). Larger satellites are often called microsatellites, while smaller satellites are called picosatellites. The term "nanosatellite" appears to have been introduced by NASA some time around 2004. It is still in the process of adoption, as many satellites of this size are simply called "small satellites."
The idea of a nanosatellite has absolutely nothing to do with nanotechnology, a term that refers the precise engineering of materials on atomic and molecular scales. From a nanoscale perspective, a 5-kg satellite looks like Mt. Everest. Nanosatellites are appealing because their small size makes them affordable and opens up the potential for a swarm of the satellites. They can piggyback on larger launches, avoiding the need for a dedicated launch. From a military perspective, a nanosatellite may be useful for the redundancy it could offer. Its small size might also help it avoid detection.
One of the earliest uses of the term "nanosatellite" was by NASA in reference to their volleyball-sized Miniature Autonomous Extravehicular Robotic Camera (Mini AERCam) satellites, which weigh about ten pounds. The purpose of this nanosatellite, which is still in testing, is to be launched from a larger parent craft and used for the purpose of inspecting the outside of a larger vehicle without necessitating a risky spacewalk. The value of such safety systems is acutely obvious, as the Space Shuttle Columbia broke up during reentry in February 2003, leading to the death of all seven crew members. This accident may have been avoided if the shuttle's heat shield was examined more closely before reentry.
As crucial electronics components such as cameras become more miniaturized, nanosatellites become possible. There is limited research in the area of nanosatellites today, as most space companies and universities focus on larger satellites, but there are signs that many are recognizing the potential of nanosatellites and conducting innovative research into them.