Supercritical magnetized collisionless shocks require ion reflection for dissipation, yet its role during formation remains unclear. Using high-power lasers, self-emission imaging, and collective Thomson scattering, we investigate a forming quasi-perpendicular shock. An upstream emission tail is consistent with a foot-like structure, while ion heating and temperature anisotropy extend upstream of a ramp-like region. These observations provide evidence of reflected-ion-related heating during early shock formation, although the incident and reflected ion populations are not separately resolved. Future measurements of ion distributions and plasma waves could clarify how this heating mediates shock dissipation and particle energization.
