INTRODUCTION to Small Satellites

Welcome

Welcome to the Small Satellites Home Page! The purpose of these pages is to provide up to date information, resources, references and links for space researchers and enthusiasts on the internet. While small satellites have literally been around since the dawn of the Space Age, large satellites and programmes have dominated the industry. However, as a reaction to reducing budgets, emphasis in the 1990's in industry on "Smaller, faster, better, cheaper" has focused increased attention on the capabilities and advantages that small satellites can bring to existing and new applications..

The pages presented here should answer such questions as "What is considered a small satellite?", and "What could you do with a small satellite?". These pages commence with a history of small satellites, and go on to show why small satellite missions have gained considerable interest. The SSHP concentrates on 'modern' small satellites, but data on many of the original small satellites has also been included. The SSHP classifies and lists past, present and future small satellite missions. Launchers are also dealt with in detail, because cost reduction is a one of the major driving forces in reducing satellites size, and small satellites therefore place challenging demands on existing launchers and launch services.

Small Satellites

Small satellites have literally been around since the dawn of the Space Age. But the success of trunk communications via satellite, coupled with manned exploration of space has forced the space industry towards ever larger and more expensive missions. Small, cheap satellites used to be the exclusive domain of scientific and amateur groups. Now major advances in microelectronics, in particular microprocessors, have made smaller satellites a viable alternative. They provide cost-effective solutions to traditional problems at a time when space budgets are decreasing.

Interest in small satellites is growing fast world-wide. Businesses, governments, universities and other organisations around the world are starting their own small satellite programmes. But what are the benefits to be gained from using small satellites? Traditionally satellites have become ever larger and more powerful. INTELSAT-6, a trunk communications satellite, has a design life of 10-14 years, weighs 4600kg at launch, and has deployed dimensions of 6.4 x 3.6 x 11.8m. It generates 2600W, and can support up to 120,000 two way telephone channels, and three TV channels. Consequently development times and satellite costs have been rising, and a single in-orbit failure can be costly. A typical modern micro-satellite weighs 50kg, has dimensions 0.6m x 0.4 x 0.3m, and generates 30W. Smaller satellites offer shorter development times, on smaller budgets and can fulfill many of the functions of their larger counterparts. As micro-satellites can benefit from leading edge technology, their design life time is often more limited by the rapid advances in technology rather than failure of the on-board systems. A perfect example of this is the Digital Store and Forward satellite UoSAT-2 launched in 1984, which is still operational in 1995. It carries an 128kbytes on-board message store and operates at 1200bps data rate, but was superceded by UoSAT-3 in 1990 with 16MByte message store, operating at 9600bps. The current satellite in this series, FASat-Alfa (1995) has 300MBytes of solid state message store, and operates at 76,800bps. The significant reductions in costs make many new applications feasible. Recently it has been recognised that small satellites can complement the services provided by the existing larger satellites, by providing cost effective solutions to specialist communications, remote sensing, rapid response science and military missions, and technology demonstrators.

"Large satellite" - Milstar-F5	"MicroSatellites" - HealthSat-2

Recently constellations of satellites have been proposed to provide voice and data communications to mobile users world-wide. These systems are divided into "Little LEO's" and "Big LEO's and MEO's". The latter offer a real time mobile voice communication systems and require medium sized and powerful satellites, but the little LEO's will provide data services, and can be successfully implemented by small satellites. These systems no doubt will establish the small satellite in the marketplace.
More...[Little LEO constellations]

After a spate of high profile failures of faster better cheaper missions, NASA reports have added "smarter" to the mantra. It was concluded that the cost may have been taken to limits where reliability was significantly affected. [ref. Spaceviews 20 Mar 2000]

Small satellite numbers

The numbers of satellites launched in the three main small satellite categories are plotted below.

Mass distribution

The mass distribution of small satellite (<500kg mass) is plotted below for the period 1980-1999. The trend line shows an upward trend, but this is deceptive. It can be seen that the number of minisatellites in the 100-500kg mass class has increased, and that their trend is towards lighter spacecraft. It could be argued that technology has permitted larger spacecraft to be built smaller making the minisatellite class spacecraft more popular.

For microsatellites the trend is also towards smaller satellites, and the first modern nanosatellites have been launched towards the end of the 1990's. The general trend is also marginally downwards, although statistics are distorted by the early Soviet military constellations and communications satellite constellations of the late 1990's.

Customers

The customer type are plotted for the period 1980-1999, as well as the yearly distribution over this period. A clear trend can be seen from military to civil small satellite missions as the primary market. Government share of small satellite missions is also growing.

Applications

The applications are plotted for the period 1980-1999, as well as the yearly distribution over this period.