The Smallest Classes of Small Satellites Including Femtosats, Picosats, Nanosats, and CubeSats

Abstract

The term small satellite (or “smallsat”) is almost intentionally vague. In fact, it covers a surprisingly broad range of miniaturized spacecraft - usually defined by its mass. The smallest type of “smallsat” is the tiny “femto satellite” that can have a mass that ranges up to 100 g (or about 3.5 ounces). The next larger class is the “pico satellite.” This type of “smallsat” is defined as ranging from 100 g to 1 kg (or about 2.2 pounds) in mass. A pico satellite is also considered to represent the mass most commonly attributed to a 1-unit CubeSat which has the dimensions of 10 cm × 10 cm × 10 cm - or a cube that is 2.53 in. on each side. Then there is the so-called nano satellite which ranges from 1 to 10 kg - often a multiunit CubeSat. CubeSats, currently, come in sizes that range from a 1-unit spacecraft up to 6 units, or the equivalent of 6 CubeSats in volume. What is sometimes overlooked when we talk of “smallsats” are miniaturized experiments which are not independent free flyers. Such systems are considered hosted payloads that can fly on larger spacecraft and derive their power, thermal control, orientation, and commands from the host satellite on which they are mounted in space. These hosted payloads can vary from a few grams to several kilograms, but are typically below 10 kg in mass. Another more recent innovation is the ability to send up experimental packages to the International Space Station (ISS). Companies that facilitate this type of small space experiments include NanoRacks for NASA or Space Applications Services for ESA. These companies manage such facilities on the ISS that are operated by astronauts to carry out experiments that are typically designed by students, academic institutions, or even small companies. This approach is highly cost-efficient especially for student experiments. Future space habitats like the Bigelow Aerospace Genesis habitats and larger facilities like the Chinese Space Station are conceived as test beds for low gravity experiments by governmental, military, corporate, or private experiments. This various types of “hosted” small-scale space missions are designed to be cost-efficient, consolidate launch operations, and also avoid the problem of creating orbital space debris. But so-called smallsats do not stop with femtosats, picosats, and nanosats. The concept of a small satellite or miniaturized satellite continues to include even larger spacecraft as well. Thus there are “microsatellites” (which are typically defined as ranging from 10 to 100 kg or up to about 220 pounds) and even so-called minisatellites ranging from 100 to 500 kg. Sometimes the range for “minisatellites” is stated as from 100 to 1000 kg, but this is less common. The spectrum of such small spacecraft sizes thus ranges from about 10 g up to 500 kg in mass. This is a gigantic range that constitutes a ratio of 1 to 50, 000 between the tiniest and the biggest of these types of spacecraft. The range is so vast that it essentially makes the term “smallsat” almost meaningless without further information. In order to make an equivalent analogy, this would be much like saying that a child’s toy airplane glider made out of balsa wood and a single-engine private airplane are the same class of aircraft. In short, one thus needs to know mass, volume, power, stabilization capabilities, operational frequencies, and more to understand what any “smallsat” actually is in fact. This chapter starts the handbook by addressing just the tiniest of “smallsats” and their uses. It discusses the characteristics and surprisingly wide range of applications of “femto satellites, " “pico satellites, " “nano satellites, " and “CubeSats” that have developed over the past 20-year period. The miniaturization of sensors, digital processors, power supplies, and other components has made these smallest of spacecraft impressively capable.