HALCA, also known as MUSES-B (Mu Space Engineering Satellite-B), was a satellite mission developed by the Japan Aerospace Exploration Agency (JAXA) in collaboration with the National Space Development Agency of Japan (NASDA) and other organizations.

HALCA was designed to serve as part of the Very Long Baseline Interferometry (VLBI) network, a global array of radio telescopes used for astronomical observations. It aimed to study celestial objects and phenomena such as active galactic nuclei, quasars, pulsars, and interstellar gas clouds with unprecedented precision and resolution.