Small Satellite Technology
Small Satellite Technology
The first satellites built by people were very small. The Soviet Union's Sputnik, which opened the Space Age in 1957, weighed only 84 kilograms (185 pounds). The American response, Explorer-1, weighed 14 kilograms (31 pounds). These early small satellites proved that it was possible to put equipment in orbit and use it, providing the first opportunities for scientific observation outside Earth's atmosphere. Explorer provided the data that led to the identification of the Van Allen radiation belts that surround Earth. Bell Labs's Telstar, about the size of a car tire, provided the first transatlantic television link, and Pioneer 10, weighing about 270 kilograms (595 pounds), was launched in 1972, and is the first satellite to leave the solar system. Thirty years after its launch, Pioneer is still functioning and was more than 7 billion miles from Earth.
Almost all satellites are powered by sunlight, and small satellites, which intercept less of this resource, are limited in power as much as they are in size, mass, and budget. However, the modern revolution in digital electronics and portable computing technologies has enabled engineers to build satellites weighing just a few kilograms that have capabilities rivaling those of older, larger satellites. Because launch costs have remained virtually constant since the beginning of the space age, small satellites and their lower costs are receiving renewed attention.
What Is a Small Satellite?
Small satellites are defined as those weighing less than 1,000 kilograms (2,204 pounds). Those below 100 kilograms (220 pounds) are referred to as microsatellites, those with a mass less than 10 kilograms (22 pounds) are known as nanosatellites, and those under 1 kilogram (2.2 pounds) are called picosatellites. However, the major difference between small and large satellites is not their weight but the way they are built. Small satellites are built by small, highly interactive teams that work with the satellite from conception through launch and operation. Large satellites are built in larger, more formally structured organizations. Small satellite teams typically have fewer than twenty members, whereas large satellites may be built by organizations with tens of thousands of people.
The small satellite team has the advantages of speed and efficiency, the ability to evaluate the implications of each design decision for the entire satellite, and the insight into all aspects of the satellite's design and application. The combination of low cost, rapid development, and low launch costs makes small satellites suitable for new applications that are not possible with larger spacecraft.
Students and hobbyists gain hands-on experience in space by building, launching, and operating satellites. Student-built satellites have hosted advanced communications experiments, astronomical and Earth-observing instruments, and video cameras that can be used to look at themselves and the satellites launched with them. Most amateur satellite activity focuses on building novel voice and digital communications links.
A very promising new application of small satellites is the inspection of larger satellites. A low-cost nanosatellite can observe the target spacecraft as it separates from its launch vehicle, deploys solar panels, and begins operations. Any problem during the initialization of operations, or later in the spacecraft's life, can be diagnosed by the escorting nanosatellite, which would have visible and infrared cameras as well as radio-based diagnostics.
Early exploration of the solar system relied on small spacecraft such as those in the Mariner series (200 kilograms [441 pounds]), the first spacecraft to visit Mars and Venus, and the Ranger (360 kilograms [794 pounds]) lunar missions. Modern interplanetary spacecraft explore their target planets and moons with the aid of robots, and these robots are also becoming very small. The Mars Sojourner, a robotic rover, weighed just 11 kilograms (24 pounds), and its host spacecraft, the Mars Pathfinder, weighed just 570 kilograms (1,257 pounds) plus 320 kilograms (705 pounds) of propellant to guide its flight from Earth to Mars. Although the development teams were large, the small size of these interplanetary spacecraft is remarkable, especially compared with large spacecraft such as the space shuttle that are needed to take human crews a few hundred miles into low Earth orbit.
The Future of Small Satellites
Because small satellites require only a corner of a laboratory, basement, or garage, plus some basic equipment for their construction, there are hundreds of small satellite developers around the world. By contrast, developers of large satellites include a few major corporations and government laboratories in the largest and wealthiest countries. The proliferation of developers and users of small spacecraft has unleashed the same creative forces that propelled the personal computer to its dominant position in the computer market.
The leading commercial developers of small satellites include AeroAstro and Surrey Satellite Technology Limited. University-based developers of small satellites include Stanford's Starlab, Weber State, the Technical University of Berlin, Technion (Israel), the University of Stellenbosch (South Africa), and the University of Mexico. Governments are building small spacecraft in labs in the United States, Canada, the United Kingdom, Israel, Spain, France, Sweden, Finland, Norway, Denmark, Russia, Japan, Australia, Malaysia, and almost 100 other countries.
The future of small satellites, and in large part the future of space exploration and application, will rely on the creativity of this diverse population of developers.
see also Communications Satellite Industry (volume 1); Satellite Industry (volume 1); Satellites, Future Designs (volume 4); Satellites, Types of (volume 1).
Fleeter, Rick. The Logic of Microspace. Torrance, CA: Microcosm Press, 2000.
Wertz, James R., and Wiley J. Larson, eds. Reducing Space Mission Cost. Torrance, CA: Microcosm Press, 1996.
——. Space Mission Analysis and Design. Torrance, CA: Microcosm Press, 1999.
Space Access See Accessing Space (Volume 1).