Optical Switch Proves its Worth Aboard ISS

SPECTRODemo has been developed as a precursor demonstrator to increase the maturity of the complete optical chain, i.e., the fiber switch and spectrometer. The payload was launched on April 17, 2019 and operated continuously until August 9, 2019. The technology demonstrator was operated aboard the ISS within the ICE Cubes Facility – a small modular container which measures 2Ux2U, where 1U=10x10x10 cm³.

The demonstrator provides useful information for the upcoming development of the Exobiology Facility flight model, especially with respect to the operation, durability, and reliability of the fiber switch.
In the fiber switch concept, each cell is associated with its own dedicated multimode optical fiber. A switch unit is used to select the fiber that is measured by the spectrometer, which allows a higher flexibility in sample handling in a compact design. The configuration of SPECTRODemo supports continuous acquisition across six channels, with each channel recording a spectrum from a defined LED source through a calibrated neutral density filter with a fixed absorbance value.

The main objective is to assess the reliability of the system and potential modifications to assure repeatable measurements and suitability for the harsh environment of space. Consequently, an environmental test campaign was performed to evaluate whether critical components can survive the launch and the space environment. The fiber switch underwent vibration and shock testing and passed successfully. Additionally, the device experienced a thermal-vacuum test in which the setup was connected electrically and optically to equipment outside the chamber to verify the system performance during testing. Overall, eight cycles between -25°C and 60°C were performed. Performance was measured at extreme temperatures, without exhibiting any malfunctions in this case as well.