ANDES, the high resolution spectrograph for the ELT: RAM strategy during the preliminary design review

RAM analysis is crucial for the success of any measurement campaign and must be implemented at the earliest design phase of building an astronomical instrument. ANDES (ArmazoNes high Dispersion Echelle Spectrograph) currently in phase B will be the high-resolution spectrograph for the ELT formerly known as ELT-HIRES. Its design in the extended version foresees four spectrographs fed by fibers and operating both in seeing and diffraction-limited (adaptive optics assisted) mode. Due to these properties strictly related to flexibility and modularity, a RAM approach focused on different scientific data requirements permits a high availability for the main data acquisition modes. To implement this process, the product tree, active elements, modularity, component duty cycles, and degraded modes were defined in the earlier phases. In this way, RAM requirements contribute to defining design. This process avoids missing the control of particular aspects like maintenance accessibility, cost of operations, and downtime due to maintenance. The paper presents the process and how it is implemented in the ANDES project, thereby suggesting a design solution for the instrument.