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The world's first micro-debris measurement demonstration experiment conducted on the ISS using the concept of conductive (resistive) strip lines for micro-debris detection

The space debris monitor (SDM) is a large-area impact sensor for in situ measurements of micro-meteoroids and space debris of the sub-millimeter to millimeter size in the near-Earth space environment. These meteoroid and debris particles are very small to be detected by ground-based observations (radars and optical telescopes) but are sufficiently large to cause serious damage to spacecraft equipment in the low Earth orbit region. The nominal detection area of the SDM is 0.1 m2 (0.35 m × 0.3 m), but its dimensions can be easily modified to accommodate different SDM constraints.

The SDM is made from a flexible printed circuit, which is produced from a thin film of a nonconductive material (such as polyimide) on which thin conductive stripes are formed in parallel. The stripe width is approximately 50μm, and the spatial separation is approximately 100μm, as shown in Figure 1. When a micro-debris particle with an effective diameter near to or larger than the spatial separation of the stripes (here approximately 100μm) collides with the sensor film at a velocity sufficient to penetrate it, one or more of the stripes are cut and become nonconductive. Debris impacts can thus be detected by monitoring the electrical conductivity (resistivity) of the stripes. This sensor system can measure the size of the incident micro-debris particles by detecting the number of severed stripes. The measurement concept is registered as a patent in many countries (US8564430, CA 2712411, CN ZL200980108349.4, UA 94873, JP 5492568, EA1906)

The first SDM was launched with HTV-5 on August 19, 2015 and represents the world's first micro-debris measurement demonstration experiment to be conducted on the ISS using the concept of conductive (resistive) strip lines for debris detection. Another type of micro-debris sensor is also on board the HTV-5 mission and is based on an impact sensor that is a piezoelectric transducer. It comprises a Chiba-koudai Debris Monitor (CDM), where six piezoelectric sensors are attached to a structure of KASPER to provide impact timing information and impact momentum. JAXA is currently conducting an analysis of the acquired data.