  Despite over 50 years of Gamma-Ray Burst (GRB) observations many open
questions remain about their nature and the environments in which the emission
takes place. Polarization measurements of the GRB prompt emission have long
been theorized to be able to answer most of these questions. The POLAR detector
was a dedicated GRB polarimeter developed by a Swiss, Chinese and Polish
collaboration. The instrument was launched, together with the second Chinese
Space Lab, the Tiangong-2, in September 2016 after which it took 6 months of
scientific data. During this period POLAR detected 55 GRBs as well as several
pulsars. From the analysis of the GRB polarization catalog we see that the
prompt emission is lowly polarized or fully unpolarized. There is, however, the
caveat that within single pulses there are strong hints of an evolving
polarization angle which washes out the polarization degree in the time
integrated analysis. Building on the success of the POLAR mission, the POLAR-2
instrument is currently under development. POLAR-2 is a Swiss, Chinese, Polish
and German collaboration and was recently approved for launch in 2024. Thanks
to its large sensitivity POLAR-2 will produce polarization measurements of at
least 50 GRBs per year with a precision equal or higher than the best results
published by POLAR. POLAR-2 thereby aims to make the prompt polarization a
standard observable and produce catalogs of the gamma-ray polarization of GRBs.
Here we will present an overview of the POLAR mission and all its scientific
measurement results. Additionally, we will present an overview of the future
POLAR-2 mission, and how it will answer some of the questions raised by the
POLAR results.
