High data rates to the ground station

Huge data quantities are generated as a result of the different experiments that are performed on the ISS (International Space Station). Transmitting the huge data quantities quickly to the ground station previously represented a bottleneck that can now be resolved using a new high-speed radio downlink. The companies Elma and SAIT have cooperated in an exemplary fashion in generating a solution.

This high-speed link earthwards is first being used to transmit data from a remote-sensing hyperspectral imager aboard of the ISS. Due to the enormous increase in the data rate, other scientists have already shown a huge amount of interest regarding this innovative data transmission technique.

The system is accommodated in a cube-shaped ATR enclosure (Air Transport Rack) from Elma, which is equipped with a modified cPCI backplane, a DC/DC converter as power supply and high-performance cooling from the system specialists in Pforzheim, Germany. And SAIT supplies the complete inner workings: A storage and interface unit handling essential functions. A specific embedded computer with a Flash drive equipped to meet the highest demands and several specially developed high-speed interfaces are used in the form of cPCI cards. Data from the scientific equipment is received via this unit through the internal ISS Ethernet network. After being buffered, the data is transferred to earth using a separate transmitter. Furthermore, the newly developed system includes the control and remote maintenance for the scientific experiments performed on the ISS and for the downlink transmitter.

In the pre-project phase, SAIT consulted with several system suppliers. These preliminary discussions indicated that an approach involving a fully integrated system with single board computer would not prove to be technically satisfactory. As a consequence, the decision was made in favour of a 19-inch system from Elma. What was especially convincing was the wealth of experience that the Elma specialists could demonstrate in the implementation of customer projects. References include the numerous applications with the highest demands on the mechanical and electrical stability that Elma has already implemented for aerospace applications. This was already reflected in the fact that a detailed and convincing concept was quickly generated in a cooperative spirit in the pre-project phase. This solution was developed, manufactured and successfully implemented based on this concept.

Significant challenges

• Modified CompactPCI backplane
• Powerful cooling
• Long lifetime and reliability
• Ruggedized
• Weight

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