Structural health monitoring
Space debris increasingly jeopardizes the satellites’ missions by risking their structural integrity and operational capabilities. Whether such debris is from the defunctionalized satellite remnants or other orbiting objects, they may introduce serious structural deformation to the satellite panels. Using sensors to measure deformation from a potential collision helps predict and minimize the risk, e.g., turning the susceptible moving parts (like MEMS devices) off when the satellite is exposed to a debris cluster/swarm. Even space radiation may introduce strain to electronics and optoelectronic devices on a microscale.
Our group has been working on Spacecraft Autonomous Collision Avoidance Systems to reduce the risk of collision, especially in Low Earth Orbit (LEO); however, measuring the strain introduced by micro-debris and space radiation is not feasible by using Lidars and visible cameras. Therefore, to measure the strain in optoelectronic devices, a photonic sensor with the potential to be integrated into photonic circuits (PICs) is of high importance since photonic devices have shown space radiation hardness, making them great candidates for such applications. Therefore, a solution was proposed for measuring the strain induced by high-energy ions, space radiation, and micro-debris [1]. The proposed device is an integrable photonic strain sensor based on a suspended Bragg grating. This also helps gather detailed information about the space micro-debris, which is less provided for the LEO.
The proposed sensor is based on a suspended Bragg grating reflector designed on the top of a Si3N4 membrane. This strain sensor is designed to operate at the communication wavelength of 1550 nm, with a small footprint (~ 100 μm2). Working on both the reflection and transmission modes, the proposed structure simplifies the readout and post-processing circuits design. Our investigations showed that the reflection varies from 11% in the rest state to 91% when the structure is under the vertical strain of 10,000 microstrains (με). The device’s transmission also changes from a maximum value of 43% down to 4.5% for the same situation (i.e., from the stable state with zero strain to a maximum of 10,000 με). Therefore, the proposed sensor and measurement method enables effective monitoring of micro-debris parameters such as size, velocity, and impact energy, making this approach beneficial for integration into smart satellites.
References
[1] M. Maleki, N. Saha, G. Brunetti and C. Ciminelli, “Design of a Photonic Strain Sensor Based on a Suspended Bragg Grating Reflector,” in 2024 It. Conf. on Opt. and Photon. (ICOP), Firenze, Italy, 2024, pp. 1-4, DOI: 10.1109/ICOP62013.2024.10803632. link https://doi.org/10.1109/ICOP62013.2024.10803632.