Monitoring needs of spacecraft are rapidly increasing due to new and more challenging missions, along with demands to reduce launching costs by minimizing the manufacture, assembly, integration and test time and employing new low weight materials balanced by the need for maximizing system lifetime while maintaining good reliability. Conventional electronic sensors are characterized by their low multiplexing capability and their EMI/RF susceptibility and it is in this scenario that Fiber Optic Sensors (FOS) in general, and more specifically Fiber Bragg Grating (FBG) technology offers important benefits, improving in various ways the already deployed sensing subsystems (e.g. reducing the weight associated with sensor cabling, increasing the number of sensing points) and enabling new monitoring applications that were not possible by using conventional sensing technologies.
This work presents the activities performed and the lessons learnt in the frame of ESA’s ARTES-5 project “Fiber Optic Sensing Subsystem for Spacecraft Health Monitoring in Telecommunication Satellites”. This project finished in July 2009, with the implementation and testing of two different demonstrators employing FBG sensor technology: FBG sensors for temperature monitoring in high voltage environments, and in particular in several parts of electric propulsion subsystems , and FBG sensors for thermal monitoring of array-antennas during RF testing .
In addition, the contacts performed with different actors within the space community allowed the identification of a special area of interest for the substitution of regular thermocouple instrumentation by FBG technology for thermal vacuum ground testing of satellites.
Fiber Optic Sensor (FOS) technology presents long recognized advantages which enable to mitigate deficient performance of conventional technology in hazard-environments common in spacecraft monitoring applications, such as: multiplexing capability, immunity to EMI/RFI, remote monitoring, small size and weight, electrical insulation, intrinsically safe operation, high sensibility and long term reliability. A key advantage is also the potential reduction of Assembly Integration and Testing (AIT) time achieved by the multiplexing capability and associated reduced harness.
In the frame of the ESA’s ARTES5.2 and FLPP-Phase 3 programs, Airbus DS-Crisa and FiberSensing are developing a Fiber Bragg Grating (FBG) – based temperature monitoring system for application in space telecommunication platforms and launchers. The development encompasses both the interrogation unit and the FBG temperature sensors and associated fiber harness.
In parallel Airbus DS - Crisa is developing a modular RTU (RTU2015) to provide maximum flexibility and mission-customization capability for RTUs maintaining the ESA’s standards at I/O interface level . In this context, the FBG interrogation unit is designed as a module to be compatible, in both physical dimensions and electrical interfaces aspects, with the Electrical Internal Interface Bus of the RTU2015, thus providing the capability for a hybrid electrical and optical monitoring system.
A novel miniature fiber Bragg grating (FBG) based temperature probe is presented. The sensor design integrates a ushape
lossless taper thus offering the advantages of a terminal temperature probe while enabling effective serial
multiplexing. We report on the experimental validation of the temperature probe design demonstrating lossless operation
and effective elimination of strain cross-sensitivity.