Towards AugerPrime: the upgrade of the Pierre Auger Observatory

The Pierre Auger Observatory has begun a major Upgrade (AugerPrime), with an emphasis on improved mass composition determination using the surface detectors of the Observatory. AugerPrime will include new 4 m2 plastic scintillator detectors on top of all the 1660 water-Cherenkov detectors, a faster and more powerful electronics, a large array of buried muon detectors, and an extended dynamic range. After introducing the physics motivation of AugerPrime, the planned detector upgrade is presented and the expected performance and improved physics sensitivity of the Observatory are discussed.