Philosophy of Micro and Nanosatellites

‘Small satellites - Big future’, title of 2010 Appleton Lecture by Prof. Sir Martin Sweeting at The Institute of Engineering&Technology on Jan 19, 2010

History of satellites started since the launching of Sputnik 1, first Earth-orbiting artificial satellite, on October 4, 1957. Interestingly, micro and nanosatellites showed their existence at the very initial stage of human space exploration. Sputnik 1 had a mass of 83.6kg while Explorer 1, first satellite of US launched at 1958, had a mass of 14kg. They are categorized as micro (<100kg) and nanosatellite (<20kg) respectively according to classification in the present day.  

  Figure 1: Sputnik-1

Figure 2: Explorer-1

As the launch vehicles capability steadily increased from 1960s onwards, larger, heavier and more complex satellites were designed and launched into the space. The trend has concerned space community about the decrease in flight opportunities, increasing cost per mission as well as long design and development life-cycle which could take more than 10 years for a complex mission. Compromised solutions had been made in integrating diverse and incompatible functions into large satellite, therefore, result in a poor and inefficient design. Failure of a system could possibly ruin the whole mission.

 Figure 3: TerreStar-1 communication satellite with a launch mass of 6910kg is the largest communication satellite ever built and launched into space on 2009-07-01.

Realizing of these demerits, microsatellites regained attention of space community. Functionalities of a large satellite were distributed into several smaller satellites which are smaller in mass, less complex and cheaper to develop. This also leads to a shorter development life-cycle and improved reliability. Design-to-cost approach, introduced at Third United Nations Conference on the Exploration and Peaceful Uses of Outer Space (UNISPACE III), Vienna, Austria, 1999 and pioneered by Surrey Satellite Technology Ltd (SSTL), utilizes existing technologies to achieve cost reduction. The approach imposes a strict constraint on cost and schedule to avoid cost overrun which is commonly seen in previous design-to-capability approach. Relatively short mission life time of microsatellites permits utilization of non-space-qualified components or known as commercial off-the-shelf (COTS) components, e.g. MEMS sensors with very low mass and low volume. These cutting edge components are generally more superior in performance than those space qualified components. At the same time, the approach is also supported by advance in electronic miniaturization and emerging of small launchers.

The microsatellite philosophy is particularly attractive for space emerging countries. These countries able to initiate their own space program now at reduced mission complexity and cost. Micro and nanosatellites have provided an affordable way for the space emerging countries to achieve space independence by putting their own communication, earth observation or defense security satellites into orbit. Performance of their microsatellites may not match with larger satellites but they have the direct control and access to the satellites without relying on major satellite service providers.

 Figure 4: SNAP-1, a 6.5kg nanosatellite developed by SSTL

Figure 5: CubeSat and InnoSat developed by ATSB 

The philosophy also benefits established space agencies. NASA has embraced on ‘faster, better, cheaper’ approach to promote a cost effective way to carry out near-Earth scientific missions and planetary explorations, e.g. it allows NASA to send at least a spacecraft to Mars during each Earth-Mars launch window in the future. They have been granted with more mission opportunities that novel technological ideas can be verified and proved in a shorter timeframe. Cost saving in microsatellite missions is approximately two orders of magnitude compare to larger satellite missions, allows the missions to be more diversified and more potential users involved. According to recent information gathered, as shown in Figure 6, a significant development in microsatellites (<100kg) over the last 10 years further verifies the potential of micro and nanosatellites.

 Figure 6: Number of micro (<100kg) and nanosatellites (<20kg) being launched into space from 1990 to 2009 (up to November 2009). From 2000 to 2009, nanosatellites (<20kg) contribute a significant proportion of total microsatellites (<100kg).