Compact spacecraft swarms could map CMB curvature at 10^-5 precision to test finite universe models

The proposal builds on Planck satellite data showing the universe is flat to within 0.4 percent by targeting smaller angular scales where curvature-induced distortions would first appear if space loops back on itself. Each 6U spacecraft carries a 100 GHz bolometer array and uses formation flying to create a virtual 100-meter baseline interferometer, bypassing atmospheric noise that limits ground-based efforts. Simulations indicate this setup could detect a positive curvature signal at 5-sigma if the universe radius is less than 10^26 meters. Related work from the LiteBIRD collaboration and the 2023 CMB-S4 white paper provides the plasma physics priors needed to separate foregrounds. The main limitation remains funding for a multi-year constellation launch, with no hardware yet built. Follow-on analysis could strengthen evidence by cross-correlating with 21-cm intensity mapping from HERA. Next steps include a 2027 technology demonstrator on a single CubeSat to validate thermal stability at 0.1 mK.