GroundMSPI_ACEPOL_Radiance_Data are GroundMSPI radiance products acquired during the Aerosol Characterization from Polarimeter and Lidar (ACEPOL) flight campaign. GroundMSPI Level 1B2 products contain radiometric and polarimetric images of clouds, aerosols, and the surface of the Earth. In particular, products contain data at 8 wavelengths: 355, 380, 445, 470, 555, 660, 865, and 935 nm. The data products include radiance, time, solar zenith, solar azimuth, view zenith, and view azimuth for all spectral bands. Wavelengths for which polarization information is available (470, 660, and 865 nm) also include the Stokes parameters Q and U, as well as degree of linear polarization (DOLP) and angle of linear polarization (AOLP). Q, U, and AOLP are reported relative to both the scattering- and view meridian planes. Files are distributed in HDF-EOS-5 format. This release of GroundMSPI data contains all targets acquired during the Aerosol Characterization from Polarimeter and Lidar (ACEPOL) flight campaign. ACEPOL was based out of Armstrong Flight Research Center in Palmdale, CA, and focused on assessing the capabilities of proposed future instruments by the ACE pre-formulation study to answer fundamental science questions associated with aerosols, clouds, air quality and global ocean ecosystems. GroundMSPI provided support for the instruments aboard the ER-2, acquiring data on October 25 and November 7, 2017.