High-resolution shape model of Ceres from stereophotoclinometry using Dawn Imaging Data

Abstract

We present a high-resolution global shape model of Ceres determined using the stereophotoclinometry technique developed at the Jet Propulsion Laboratory by processing Dawn's Framing Camera data acquired during Approach to post-Low Altitude Mapping Orbit (LAMO) phases of the mission. A total of about 38,000 images were processed with pixel resolutions ranging from 35.6 km/pixel to 35 m/pixel and the final global shape model was produced with 100-m grid spacing. The final SPC-derived topography was computed relative to the (482 km, 482 km, 446 km) mean ellipsoid, which ranges from −7.3 km to 9.5 km. For the purpose of validation, we performed various error analyses to assess and quantify realistic uncertainties in the derived topography, such as dividing the data into different subsets and re-computing the entire topography. Based on these studies, we show that the average total height error of the final global topography model is 10.2 m and 88.9% of the surface has the total height error below 20 m. We also provide improved estimates of several physical parameters of Ceres. The resulting GM estimate is (62.62905 ± 0.00035) km3/s2, or the mass value of (938.392 ± 0.005) × 1018 kg. The volume estimate is (434.13 ± 0.50) × 106 km3 with a volumetric mean radius of 469.72 km. Combined with the mass estimate, the resulting bulk density is (2161.6 ± 2.5) kg/m3. Other improved parameters include the pole right ascension, α0 = (291.42763 ± 0.0002)°, pole declination, δ0 = (66.76033 ± 0.0002)°, and prime meridian and rotation rate of (W0 = 170.309 ± 0.011)° and (dW/dt = 952.1532635 ± 0.000002) deg/day, respectively. Also, for geophysical and geological studies, we provide spherical harmonic coefficients and a gravitational slope map derived from the global shape model.