Satellites, like Dairy Milk, Mars Bars and Snickers, are getting smaller these days. Factors contributing to this shrinkage include new technology, continued miniaturisation of computing components and increased launch costs â€“ whereas smaller size equals less weight and less weight equals lower costs.
According to the Union of Concerned Scientists database at the end of August 2015, the total launch weight of all satellites still in orbit is approximately two and half million kilograms! A sobering thought given that most of these are travelling in excess of seventeen thousand miles per hour! The Guinness Book of Records lists the heaviest commercial satellite as TerreStar-1 that had a launch mass of 6 903.8 kg in 2009; whereas the heaviest payload is the Chandra X-Ray Observatory Telescope that had a weight of 22 753 kg when launched in 1999. Although, it should be noted there are number of large military satellites in space whose launch weight cannot be verified. However, everyone can agree that these satellites are large and heavy!
Smaller satellites have been around since 2000, but it wasnâ€™t until 2013 when 92 smaller satellites were launched in a single year that the numbers became significant. There are a number of categories of small satellites:
- Minisatellites have a mass of between 100 kg and 500 kg.
- Microsatellites have a mass between 10 kg and 100 kg.
- Nanosatellites have a mass between 1 kg and 10 kg.
- Picosatellites have a mass between 0.1 kg and 1 kg.
- Femtosatellites have a mass between 10 g and 100 g.
Smaller satellites do have technical challenges. These include shorter overall life, limitations on propulsion and manoeuvring capabilities, less computing power and very low bandwidth communication systems. There have been a number of innovative solutions developed to respond these challenges, for example the UK company Oxford Space Systems have developed deployable structures, such as antennas and solar panels, based on the principles of origami using â€˜shape memoryâ€™ materials. This has resulted in lighter, simple and cheaper deployable structures, for example, they have a parabolic antenna scalable up to twelve metres.
Technical issues are not the only challenges for small satellites, the regularity framework has not yet adapted to the changing market. As weâ€™ve discussed previously, within the UK the Outer Space Act 1986 details the regulations for satellite launches. These are based around large satellites, and are not at all favourable to small satellites. The UK Space Agency recently issued a series of recommendations on how the regulatory approach might be tailored for smaller satellites.
Smaller satellites offer a more flexible, and cheaper, way of getting sensors and experiments into space. While this is great for smaller companies and educational institutes; commercial organisations are also taking advantage of this new trend. It will be interesting to see if the trend for smaller satellites continues to grow or, like mobile phones, the miniaturisation ceases and they get bigger again!