Spherical harmonic models of the shape of asteroid (1) Ceres [DLR SPG]

This archive contains four spherical harmonic models of the shape of asteroid (1) Ceres, truncated at different maximum spherical harmonic degrees. The highest resolution model has a maximum spherical harmonic degree of 5399, which was generated from a shape model sampled at 60 pixels per degree.

The data used to generate these models are from a DLR stereo photogrammetric shape model based on Dawn high altitude mapping orbit framing camera images, as found in the file CE_HAMO_G_00N_180E_EQU_DTM.IMG on NASA's PDS website. This image file was first converted to netcdf format using the generic-mapping-tools function xyz2grd, it was then converted to a gridline registration using the function grdsample, and the resulting netcdf file was read into the pyshtools software and expanded into spherical harmonics using the function SHCoeffs.expand(). The spherical harmonic functions were chosen to be "4pi" normalized and to exclude the Condon-Shortley phase factor of (-1)^m. The units of the coefficients are meters.

The four files in this archive are

• Ceres_DLR_SPG_shape_5399.bshc.gz
• Ceres_DLR_SPG_shape_2879.bshc.gz
• Ceres_DLR_SPG_shape_1439.bshc.gz
• Ceres_DLR_SPG_shape_719.bshc.gz

The numbers 5399, 2879, 1439, and 719 in the filename refer to the maximum spherical harmonic degree of file, which corresponds to effective spatial resolutions of 60, 32, 16, and 8 pixels per degree, respectively. The files are stored in the binary "bshc" format as described in the pyshtools documentation and are furthermore compressed using gzip. The lower resolution models were generated by truncating the spherical harmonic coefficients of the highest resolution model.