  We perform a cosmic shear analysis in harmonic space using the first year of
data collected by the Dark Energy Survey (DES-Y1). We measure the cosmic weak
lensing shear power spectra using the Metacalibration catalogue and perform a
likelihood analysis within the framework of CosmoSIS. We set scale cuts based
on baryonic effects contamination and model redshift and shear calibration
uncertainties as well as intrinsic alignments. We adopt as fiducial covariance
matrix an analytical computation accounting for the mask geometry in the
Gaussian term, including non-Gaussian contributions. A suite of 1200 lognormal
simulations is used to validate the harmonic space pipeline and the covariance
matrix. We perform a series of stress tests to gauge the robustness of the
harmonic space analysis. Finally, we use the DES-Y1 pipeline in configuration
space to perform a similar likelihood analysis and compare both results,
demonstrating their compatibility in estimating the cosmological parameters
$S_8$, $\sigma_8$ and $\Omega_m$. The methods implemented and validated in this
paper will allow us to perform a consistent harmonic space analysis in the
upcoming DES data.
