The ATLAS New Small Wheel new Muon Stations Ready for LHC Run3

After nearly a decade of intense effort, the two New Small Wheels (NSW) for the upgrade of the atlas muon spectrometer are now installed in the experiment and ready for final commissioning and to collect data in LHC Run3, starting March 2022. The NSW is the largest phase-1 upgrade project of ATLAS. Its challenging completion and readiness for data taking is a remarkable achievement of the collaboration. The two wheels (10 meters in diameter) replace the first muon stations in the high-rapidity regions of ATLAS and are equipped with multiple layers of two completely new detector technologies: the small strips Thin Gap Chambers (sTGC) and the Micromegas (MM). The latter, belongs to the family of Micro Pattern Gaseous Detectors (MPGD, for the first time used in such a large scale in HEP experiments). Each of the detector technologies will cover more than $1200$ $m^{2}$ of active area. The new system is required to maintain the same level of efficiency and momentum resolution of the present detector, in the expected higher background level in view of the ongoing series of LHC luminosity upgrades. In addition, it is necessary to keep an acceptable muon trigger rate with the same Muon momentum threshold.