## 1 Introduction  
NASA has selected 12 new science and technology payloads, useful for the study of the Moon and to explore more of its surface as part of the Agency's Artemis lunar program [1, 2]. These investigations and demonstrations will help the Agency to send astronauts to the Moon by 2024 as a way to prepare to send humans to Mars for the first time. The selected investigations will go to the Moon on future flights through NASA's Commercial Lunar Payloads Service (CLPS) projects [3]. Many of the new selections incorporate existing hardware such as parts or models designed for missions that have already flown [4]. Seven of the new selections are focused on answering questions in planetary science or heliophysics while five demonstrate new technologies. One of these 12 payloads is a new class of Lunar Laser Ranging (LLR) experiment recently investigated by international Space Agencies, named NGLR, a new concept of Cube Corner Retroreflector (CCR) to be deployed on the moon's surface. The NGLR experiment is basically a single CCR whose diameter is 100 mm that must be pointed from the Moon toward the mean Earth direction. The experiment is aimed to be integrated on a lander deck, and no robotic arm is provided for its deployment.  
A simplified pointing system for the CCR could make use of a mechanism formed by a passive cardan magnetic suspension, able to compensate for the misalignment due to the slope of the landing site that can be consistent [5], dedicated to the alignment of the CCR toward the mean Earth direction. PM bearings, providing radial trust, that are embedded in the cardan suspension for alignment by gravity of the elevation and polarization angle of the device, represent a preferred option in order to deal with the short life demonstrated by Apollo's missions' mechanisms, due to the electrostatic charged nature of Moon dust and the continuous stream of solar wind ionized particles sweeping the regolith [6; 7].  
Such a system can be applied to any devices in needs of permanent pointing from Moon to Earth such as telemetry antennas. With reference to a commercially available pointing mechanism, which can be complex and expensive [8], the solution does not require actuators, representing an important improvement in terms of the mass, cost and reliability of the alignment system; regarding elevation and polarization angles, it is a passive system without the provision of electrical power by the lander.  
A sketch of the NGLR experiment cardan suspension layout is illustrated in Figure 1.  
According to Earnshaw's Theorem, it is not possible to fully stabilize an object using only a stationary magnetic field [9; 10; 11]. It is necessary to also provide axial control of the shaft since the PM bearings support the radial load, but they produce an unstable axial force when losing alignment between the stator and rotor magnets stack. The axial phasing between the rotor and the stator magnets must be accurately maintained in order to maximize the radial trust performances of the bearing. This mechanical phasing is opposed by the axial force between the stacks, which generates and tends to increase with the loss of relative nominal alignment [12]. For this reason, axial load bearings must be provided in the system design. A possible solution for stabilizing magnetic suspension in space applications considers the use of the so-called jewel bearings (JBs) where an element, normally a plate when only axial capability is required, made of synthetic sapphire [13], is axially engaged with a metal spindle. The main goal of this work is to report about the preliminary tests of COTS JB, available by Swiss Jewel Company, engaged with different material spindles. The sapphires have been subjected to the vibrational loads typical of a space mission. At the end of the tests and analysis of the results a strategy on materials and design has been developed.