The challenge of miniaturisation for space applications

By miniaturising spacecraft and reducing their mass, we can grant easier access to space at a lower cost. Small satellites will therefore be categorised based on their mass, although this classification is not yet standardised:
  • Femtosatellite : mass < 100 g
  • Picosatellite : mass < 1 kg
  • Nanosatellite : mass < 1–50 kg
  • Microsatellite : mass < 100–150 kg (NASA < 100 kg)
  • Minisatellite: mass  < 500 kg (NASA smallsatellite < 180 kg)

Scale and categories of small satellites – Source: NASA, Small Spacecraft Technology State of the Art 2014

 What are nanosatellites?

Nanosatellites are a new category of space instruments that range from 1 kg to 50 kg and are primarily characterised by their small size, although what truly makes them interesting is their standardisation. What’s more, these instruments consume less energy compared to large spacecraft.

Diagram of a cubesat nanosatellite showing the different constituent parts – Source: ‘Nanosatellites – réflexions’, ESEP, Dec. 2014

How the cubesat was born

Cubesats were created in 1999 as the result of collaborative work between Professor Jordi Puig-Suari from California Polytechnic State University (Cal Poly) in San Luis Obispo and Professor Bob Twiggs from Stanford University’s Space and Systems Development Laboratory (SSDL). The goal was to develop standard small satellites at a lower cost, thus allowing the universities to produce and launch their own spacecraft. A cubesat is a standard nanosatellite in the shape of a cube measuring one cubic decimetre. Its volume is therefore one litre and should weigh less than 1.33 kg (see image below, taken from CubeSat Design Specification Rev. 13, The CubeSat Program, Cal Poly SLO).

Due to their standardisation, cubesats can be assembled with a view to building larger satellites in the event of greater payloads. In order for the universities to launch their cubesats into space, a deployment system was built by Cal Poly (the Poly Picosatellite Orbital Deployer, or P-POD) to serve as an interface between the launch vehicle and the cubesats. Once in orbit, a signal is sent from the launch vehicle to the P-POD to open the door and eject the cubesats.

The maximum capacity is three cubesats per P-POD (see image below: ‘Six CubeSats and their deployment systems (P-POD)’ – Source: CubeSat Design Specification Rev. 13, The CubeSat Program, Cal Poly SLO).

Small instruments with enormous scientific potential

The advantages of nanosatellites and cubesats over traditional spacecraft are the following:
  • Easier access to space technology: for SMEs (small- and medium-sized enterprises), laboratories and students

  • Design time: the production time for a nanosatellite is approximately five years, which is much shorter than for traditional spacecraft

  • Lower costs: the approximate cost is €1.5 million, compared to several tens of millions for standard satellites

Long considered only for teaching purposes due to their standardisation and ease of production, the vision for and use of nanosatellites changed radically in 2003 after the launch of MOST, a Canadian nanosatellite project. The MOST mini-telescope (Microvariability and Oscillations of STars) was actually the first nanosatellite to carry out a scientific mission, its role being to study stellar seismology.

Consequently, for more than a decade now, these small craft have gone from strength to strength, attracting the attention of a wide range of players (universities, laboratories, industrialists and SMEs) thanks to the endless variety of scientific subjects, technological demonstrations, experiments in orbit and so many other things that can be allocated as payloads to these small instruments with their deceptive capacity.