What Is a Nano-Satellite?
General Satellite Definitions
You’ve probably heard terms like CubeSat, NanoSat and Picosat thrown around increasingly often lately in news articles and blog posts, however usually without much explanatory information beyond “It’s a small satellite”. Luckily it’s not too difficult!
Satellites are defined in different classes according to their mass.The satellites you are used to thinking about are generally fairly large and heavy, falling into the ‘Large Satellite’ or ‘Medium Satellite’ category. Everything below 500Kg is termed a ‘Small Satellite’. However just to make things confusing, this category can be broken down even further!
Shown in the table are the first four common categories of small satellite. There are other categories at even lower masses but they aren’t commonplace… yet.
|Large Satellites||More than 1000 Kg|
|Medium Satellites||500 - 1000 Kg||Small Satellites|
|Mini Satellites||100 - 500 Kg|
|Micro Satellites||10 - 100 Kg|
|Nano Satellites||1 - 10 Kg|
|Pico Satellites||0.1 - 1 Kg|
NanoSat Form Factors
Alright so now you have the mass definitions down, it’s time to talk about shapes. Pretty much every medium and large satellite is a fully custom built machine that costs millions – if not billions – of dollars, takes years of development and looks something like these pictures below.
However in the nano-satellite world, the majority of satellites all look pretty much the same. The reason for this is that back around the year 2000 the California Polytechnic State University (sometimes referred to as CALPOLY) developed something called the CubeSat Specification. The document outlines what was the first ever standardised satellite design specification that would set the foundation for the explosion of new nano-satellites in the last two decades.
The CALPOLY design spec bases it’s nano satellite design on 10cm unit cubes. The smallest satellite – a 1-Unit (1U) – is nominally a 10cm x 10cm x 10cm cube and has a mass of 1.33kg, while larger satellites can be made by stacking units on top of each other – for example a 2U is 10cm x 10cm x 20cm. The spec only goes up to 3U, however nowadays 6U or even 12U can be made. It goes the other way too! Organisations have created 1/4U and 1/2U which are smaller than the original base unit. Just remember that however many ‘U’ it is, it just means that there are that many 10cm cubic volumes.
Perhaps the most important aspect of the CubeSat specification is that CALPOLY designed it to fit a launcher they called the P-POD. The interfaces, materials and allowed external dimensions of the satellite were defined to ensure the CubeSat would easily sit in the P-POD, which in turn could be easily installed into the majority of rockets. More impressively, the most common type of P-POD is a 3U which means it can fit 1 x 3U satellite or 3 x 1Us or 1 x 1U and 1 x 2U… you get the picture. this changed the space industry drastically as now anyone could build their own satellite and – as long as it complied with the CALPOLY specification – they could get it launched on any rocket equipped with a P-POD.
CubeSats are still the most well known, and most numerous, type of nano-satellite today. Other companies such as RocketLabs, Integrated Solutions In Space, and NanoRacks have come up with their own launchers that are essentially the same as the P-POD but with slight dimensional differences.
PocketQubes are essentially the fractional 1/2U cubesats mentioned above however with some differences. In 2009 the PocketQube concept was proposed in a collaboration between Morehead State University and Kentucky Space and it has very recently had an update with a new design standard released in June 2018 (Found here). The base unit is referred to as 1P and is a 5cm x 5cm x 5cm cube. Like the CubeSat, they go up from there but not in the same way. Where a 2U CubeSat is double the height of a 1U, a 2P PocketQube is more than double the height of a 1P.
The deployment mechanism also differs slightly from CubeSats – which tend to be slide along the internal rails of the P-POD – because they are so small. The PocketQubes are mounted to a backing plate which slides along the deployer similar to the CubeSat rails do. As such the deployers of PocketQubes are also different to the P-POD, and commercial variants are being developed. See here for an example.
In the last year or so information has emerged about a new, smaller, standard satellite package called the SunCube. This standard, developed by Arizona State University (ASU) is a minuscule 3cm x 3cm x 3cm and weighs only 100g!
ASU has also developed the FemtoSat Packager and Orbital Deployer (F-POD) which is a modified 1U CubeSat that can hold 27 1F SunCubes. The brilliance behind this deployer is that because it is essentially a cubesat, it can be placed on any launch mission that has CubeSat deployers installed and you get 27 satellites in the space (and cost) of 1! Indeed with this method, launch costs for these tiny satellites may potentially fall to as low as US$1000 in the future.
Finally we come to the TubeSat. These funky looking satellites differ from the prevailing cube shape and instead are – you guessed it – a tube!
The TubeSat was developed by InterOrbital Systems and are both smaller and cheaper than a CubeSat. Tubesats don’t have a conventional chassis, instead they are mainly a circular PCB stack with aluminium standoffs to provide some rigidity, and then some mounting infrastructure to attach the external Solar Panels. The TubeSat design specification can be found here.