Introduction The current generation of ground- and space-based Cosmic Microwave Background (CMB) telescopes demands highly precise calibration procedures. However, commonly used celestial polarized sources, such as Tau-A, are not characterized with the level of accuracy required for these experiments. This limitation has motivated several initiatives aimed at developing well-characterized artificial signal sources onboard aerial platforms, enabling observations from the telescopes' far-field.Methods In this context, we propose the deployment of a polarized signal source operating in the W-band (75-110 GHz) onboard a dedicated calibration satellite, referred to as CalSat, in Low Earth Orbit (LEO). This platform would facilitate the calibration of ground-based CMB polarization experiments with significantly improved accuracy compared to traditional celestial sources. During calibration operations, the LEO-based CalSat would emit purely polarized microwave radiation from the far field, directed toward the CMB telescopes.Results Moreover, LEO-CalSat could also contribute to the calibration of space-based missions operating at the second Lagrange point (L2) by enhancing the characterization of polarized celestial sources, while simultaneously increasing the Technology Readiness Level (TRL) for the future deployment of a calibration satellite at L2. Various launch and satellite platform options are currently under consideration, including Spectrum shuttles and/or MIURA launchers, as well as micro-satellites such as UPMSat-4 and CubeSats.Discussion The anticipated launch date for the LEO-CalSat mission, which targets an orbital altitude of at least 400 km, is initially scheduled for the first half of 2026. Within our collaboration, the Universidad Polit & eacute;cnica de Madrid (UPM) team is responsible for the satellite's design and development, while the IFCA/IPMU team is tasked with the development of the payload signal source.