Why are Satellites Produced in Cleanrooms?

During the manufacturing, assembly, transportation, testing, launching and duty processes, foreign substances could be remained, or later be discovered, in the system, which may cause shortening the lifetime of spacecraft and losing their functions partially or completely. These substances are generally called as pollutants.

The pollutants are fundamentally classified in two separate groups; molecular-scale pollutants and particulate pollutants

The molecular-scale pollutants are foreign substances shaped in thin films or liquid drops, or else exist in gas form. These substances could stick onto spacecraft during production or assembly. Additionally, highly radiated and vacuumed conditions of the spacecraft could cause substances to diffuse from spacecraft materials (For instance, the plastic-alike smell in new cars is caused by the same reason.). 

The particulate pollutants are micro-scaled and bigger-sized pollutants. The particulate pollutants (For example; dusts, pollens, dead skin cells, substances produced by metallic corrosion, metallic or non-metallic substances produced during manufacturing and assembly) could stick onto the surface of components forming the spacecraft during the production, assembly, transportation, storage and testing phases.

The pollutants may cause different problems in the spacecraft. The molecular-scale pollutants and particulate pollutants on the surface of the optic spacecraft components (For example; devices such as reflectors used in telescopes, photometers which calculate the direction, density and polarization of the light, radiometers, spectrometers and polarimeters) might prevent these devices to function properly by altering their light-reflecting and light-absorbing properties. 

The pollutants may also cause problems in terms of keeping the thermal balance in the spacecraft. Since there is no air in the space, a heat transfer in the spacecraft is achieved through radiation and transmission. In order to keep the temperature of spacecraft and its inner devices at constant level, the parts of the spacecraft with high heat loss is produced by materials with high light-absorbing property, while the parts of the spacecraft facing toward sun are produced by materials with high light-reflecting property. The pollutants that stick onto the surface of those materials could cause overheating or overcooling by altering light-reflecting and light-absorbing properties of the material, thus, preventing them to function properly. 

The particulate pollutants might cause serious problems especially in the fuel system of the spacecraft. For example, the possible cause of the problem faced in Russian-owned space rocket named as Soyuz, which crashed in Siberia shortly after its launch in 2011, was identified as the pollutants in fuel channels, causing a shutdown in one of the rockets by preventing adequate amount of fuel to reach to the engine.  

In order to prevent the pollutant problem in the spacecraft, it should be paid attention to select materials that do not diffuse molecular-scale pollutants in conditions of high-radiation and vacuumed (For example; Kevlar, aluminium and beryllium mirrors).

Different cleaning procedures are applied to remove pollutants released during the components’ production. Additionally, the assembly and cleaning processes of spacecraft are performed in cleanrooms.

The cleanroom is an environment in which the amount of particle hanging in the air is below certain limit value. There are different cleanroom classifications and these classifications are designed depending on the amount of particles with a certain size in one cubic meter air. For example, in TUBITAK UZAY, the space Technologies Research Institute, the assembly and testing processes of satellites are performed in the cleanroom –located in Satellite Assembly, Integration and Testing Laboratories – installed by Demiralp Cleanroom Technologies.