Gamma-ray bursts (GRBs) are the most luminous events in the universe, detectable over cosmological distances. They are associated with the death of massive stars or with the gravitational merger of binary neutron star systems, both events emitting an ultra-relativistic jet in which the gamma-ray dominated prompt emission is produced. Then, the jet slows down in the surrounding medium and generates the so-called afterglow emission, detectable over the entire electromagnetic spectrum. However, the exact mechanism through which the GRB prompt emission is generated is still largely debated. A polarization measurement of the gamma-ray emission would bring a better understanding of these objects. COMCUBE is a project of the European programme AHEAD2020 aiming at the development of a gamma-ray telescope and polarimeter in the MeV range, based on Compton scattering. This project aims at launching a CubeSat constellation, capable of monitoring the gamma-ray sky to look for gamma-ray bursts, and measure the linear polarization of the brightest ones. I will present the instrumental developments on this Compton telescope and polarimeter. I will first focus on the new developments of a calorimeter module used in the proposed instrument. It uses a cerium bromide scintillating cristal optically coupled to a pixelated photo-sensor, and allows to reconstruct the position of interaction of the gamma-ray (with a precision of approximately 2 mm) by using machine learning techniques. I will then present the first prototype of COMCUBE's Compton telescope. It uses a double-sided silicon stripped detector and a calorimeter module. The data taken with this prototype show a good agreement with simulation. Finally, I present the results of the extensive simulation work that has been conducted to design the scientific payload and to give a first assessment of the performances of COMCUBE. It will detect several GRBs per week and measure the polarization of approximately ten GRBs per year.
