This document contains the high-level overview of the DART Shape Model Didymos v003 Data Collection. Data Set Overview =============================================================================== This data collection contains a set of digital terrain maps and ancillary information (slope, magnitude of gravity, etc) for didymos_model_v003. To learn about the model including its quality, see 'Daly et al., 2023. "Successful Kinetic Impact into an Asteroid for Planetary Defense." Nature 1–3. https://doi.org/10.1038/s41586-023-05810-5." See SIS for details on ancillary information provided. Data =============================================================================== The DART SOC provides digital terrain maps in two formats, OBJ and FITS (image cubes), derived using stereophotoclinometry (SPC). SPC combines stereo techniques with photoclinometry to derive the tilt of an asteroid’s surface. This shape modeling technique estimates surface tilts at each pixel of a given image by initially using stereo parallax, and a photometric function, to constrain a relationship between a surface’s tilt and observed albedo. With this relationship in hand, the tilts of a piece of asteroid surface imaged at multiple emission and incidence angles can be obtained via least-squares that best duplicates the input images. Once the surface tilts are obtained, the geometric height across each map can be determined by integrating over the tilts in a logical manner. These individual terrain maps (called “maplets”) of the surface can then be joined together to produce global and local digital terrain models. SPC processing includes the use of asteroid limb and terminator data to initially constrain the shape of an asteroid. For more details on SPC processing see Daly et al., 2023; Gaskell, 2011; Gaskell et al., 2008, 2023; Palmer et al., 2022; Weirich et al., 2022. Shape model PDS4 data product are described as follows: 1) Digital Terrain Models (DTMs) in OBJ file format, which is a special-case ASCII Table used to describe 3-dimensional shapes. 2) Digital Terrain Models (DTMs) in multi-band FITS files with a single Header Data Unit (HDU) containing header metadata records and a data unit containing planes with units appropriate to each geophysical calculation. 3) Shape model ancillary FITS files are derived from SPC-generated DTMs, the process of which is described in detail in the dart_shapemodel_sis document. The shape (digital terrain) model will be named according to the following conventions, using all lower-case characters in the filename: Target + “_” + Coverage Type + “_” + Ground Sample Distance + “mm” + “_SPC_” + Description + “_” + “Center Location” + “_” + “v” + Version + “.” + PDS Type The Target description provides the name of the asteroid for which the product is provided: dimorphos-> Dimorphos didymos -> Didymos The Coverage Type will be: g for global l for local (regional). Used for both global tileset and site specific products. The Ground Sample Distance (resolution) is four digits expressed in millimeters (mm). The Source/Processing Type is: SPC --> Product generated using stereophotoclinometry The Description legend is as follows: obj --> Global or local shape model. dtm --> FITS file that contains a complete set of DTM planes. For ancillary FITS files, the description refers to the values that are stored in the binary FITS table. A value is provided for each plate in the corresponding DTM file. Section 5.2.1.4, Table 6 of the SIS contains the Description string for the different ancillary products. An example of the file naming convention is: dimorphos_l_0320mm_spc_dtm _1000n21000_v001.fits where 1000N represents latitude of 10.00N, 210.00 represents 210.00 East longitude and 00320mm is for 320-mm gsd. This product was generated using stereophotoclinometry for target asteroid Dimorphos. The DTM means it is a plane-relative DTM. ‘v001’ is the product version number without decimal points.