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Abstract

The Trans-Iron Galactic Element Recorder for the International Space Station (TIGERISS) is under construction and is planned for launch in 2027 and will be attached at the SOX location on the Columbus module on the ISS. TIGERISS will make the first definitive measurements of Ultra-Heavy Galactic Cosmic Rays (UHGCRs; Z >29) on an individual element basis past barium ($^{56}$Ba), through the lanthinides, and to lead ($^{82}$Pb). TIGERISS has a geometry factor of 1.06 m$^2$ sr and is comprised of four planes of single-sided silicon strip detectors (SSDs) arranged in orthogonal X-Y layers with an X-Y pair above and an X-Y pair below two large-area Cherenkov detectors. The top Cherenkov detector is comprised of a mosaic of aerogel radiators (n =1.05) while the bottom Cherenkov detector has an acrylic radiator (n = 1.49). The combination of the Cherenkov velocity measurements with the precise measurements of the ionization and trajectory of the traversing cosmic rays leads to highly accurate charge measurements of $<$ 0.25 c.u. over the entire elemental range of $^5$B through $^{82}$Pb. These TIGERISS measurements are highly sensitive in determining the strength of s-process, r-process, and rp-processes of Galactic nucleosynthesis while providing critical data needed for multi-messenger studies to determine the contributions of extreme phenomena, including supernovae (SN) and Neutron Star Mergers (NSMs), in the production of galactic matter. The science goals of TIGERISS, mission status, instrument design and performance of the TIGERISS SSD subsystem in relation to the measurements and science goals of TIGERISS are discussed in this paper.