This document contains the high-level overview of the DART Shape Model Dimorphos 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 dimorphos_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.

4) All products were released to the public while in lien resolution, with one DTM product known to have issues
with their QUALITY and SIGMA planes.  During lien resolution the issue was resolved, but the DTM product and 
corresponding OBJ product had to be completely regenerated.  Due to the old products being publicly available for 
six months, it was decided to include both in the archive.  The user is advised to use the newer superseding products.

Old "DRAFT" files (generated 2023-10-18/26):
* data_derived_dimorphos_model_v004/dimorphos_l_0050mm_spc_dtm_0896s25122_v004.{fits,xml}
	LIDVID: urn:nasa:pds:dart_shapemodel:data_derived_dimorphos_model_v003:dimorphos_l_00050mm_spc_dtm_0884s26430_v003::1.0
* data_derived_dimorphos_model_v004/dimorphos_l_0050mm_spc_obj_0896s25122_v004.{obj,xml}
	LIDVID: urn:nasa:pds:dart_shapemodel:data_derived_dimorphos_model_v003:dimorphos_l_00050mm_spc_obj_0884s26430_v003::1.0
	
New files (generated 2023-11-17):
* data_derived_dimorphos_model_v004/dimorphos_l_0050mm_spc_dtm_0897s26313_v004.{fits,xml}
	LIDVID: urn:nasa:pds:dart_shapemodel:data_derived_dimorphos_model_v003:dimorphos_l_0050mm_spc_dtm_0883s26429_v003::1.0
* data_derived_dimorphos_model_v004/dimorphos_l_0050mm_spc_obj_0897s26313_v004.{obj,xml}
	LIDVID: urn:nasa:pds:dart_shapemodel:data_derived_dimorphos_model_v003:dimorphos_l_0050mm_spc_obj_0883s26429_v003::1.0