  The very low statistics of cosmic rays above the knee region make their study
possible only through the detection of the extensive air showers (EAS) produced
by their interaction with the constituents of the atmosphere. The Pierre Auger
Observatory located in Argentina is the largest high energy cosmic-ray
detection array in the world, composed of fluorescence telescopes, particle
detectors on the ground and radio antennas. The Auger Engineering Radio Array
(AERA) is composed of 153 autonomous radio stations that sample the radio
emission of the extensive air showers in the 30 MHz to 80 MHz frequency range.
It covers a surface of 17 km$^2$, has a 2$\pi$ sensitivity to arrival
directions of ultra-high energy cosmic rays (UHECR) and provides a duty cycle
close to 100\%. The electric field emitted by the secondary particles of an air
shower is highly correlated to the primary cosmic ray characteristics like
energy and mass, and the emission mechanisms are meanwhile well understood. In
this contribution, recent progress on the reconstruction of the mass
composition and energy measurements with AERA will be presented.
