## 2 ARCHES LIBS Module
### Hardware Description
Since the used AvaSpec-Mini was originally purchased for Raman spectroscopy, a 50 \(\upmu\)m slit was chosen for higher optical throughput. Typically,  
Figure 4: The instrument’s laser beam profile near the plane of the baffle, where samples are located during measurements, is roughly elliptical, with a \(FWHM\) along the major axis of approximately 90 \(\upmu\)m and a \(FWHM\) along the minor axis of about 40 \(\upmu\)m. Due to geometrical constraints, the measurement was conducted approximately 4.5 mm outside of the exit plane of the baffle. Figure 3: CAD model of LIBS measurement head. The laser exits the measurement head towards the ground. A baffle ensures that the instrument is positioned at the appropriate distance to the target with respect to the focal plane of the laser beam. better resolution is desired for LIBS, and in future upgrades, a smaller slit can enhance the quality of the LIBS data. It is important to note that the optical path for plasma emission is not optimized for maximum light-gathering capacity; for instance, half of the unpolarized plasma emission is rejected at the polarizing beam splitter. Additionally, the 200 um pixel height of the spectrometer would allow for a larger fiber core diameter to collect more light from a broader region of the plasma. However, to prevent detector saturation of the spectrometer at strong emission lines observed during development, a smaller 100 um fiber was chosen. For the same reason, a polarizing beam splitter was chosen over a dichroic beam splitter, even though the latter can achieve higher transmission for plasma emission. The presented configuration aims for effective utilization of the spectrometer's dynamic range while leaving enough headroom for materials with strong emission lines. With the chosen optics configuration, the amount of collected plasma emission and the sensitivity of the spectrometer allow for a high signal-to-noise ratio (SNR) in the LIBS data obtained from a single laser-induced plasma. This, in turn, enables short spectrometer exposure times around the laser pulse, virtually eliminating unwanted background signals from ambient light. An exposure time of 100 us is used to account for the drift and jitter of the laser pulse timing. The laser manufacturer states a jitter of 1 us. As the laser is passively Q-switched, control is limited to the start of its pump pulse. The actual release time of the laser pulse drifts with the pump diode temperature, which is uncontrolled in our setup. The generous 100 us time window, with a 60 us delay after the pump pulse trigger, allows for capturing the plasma emission under all operating conditions while being short enough to minimize the detector dark current and the influence of ambient light. All hardware components are under the control of a LutePanda single-board computer (SBC). The SBC also interfaces with a temperature and humidity sensor (DHT11), providing information about the environment inside the payload box during rover operations. Electrical power is supplied through the docking interface between the rover's robotic arm and the payload box. A power distribution unit (PDU), integrated into the standardized payload box system, distributes electrical power to all instrument components (refer to Figure 1). The payload box infrastructure facilitates communication between the instrument and the rover. Alongside the PDU, this combination forms the Management Unit of the payload box system as illustrated in Figure 5.  
All LIBS instrument components collectively weigh approximately 1 kg, well below the total weight limit imposed by the LRU2 robotic arm. To minimize the added torque to the robotic arm's movement, all instrument components were strategically positioned close to the docking interface at the backside of the payload box.