Spacecraft Catalog

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A “spacecraft” catalog file defines the spacecraft trajectory, orientation, appearance, name label, and trajectory plot parameters for a spacecraft. This is an example of spacecraft catalog file for CASSINI:
{
   "version": "1.0",
   "name": "Cosmographia CASSINI Example",
   "items": [
      {
         "class": "spacecraft",
         "name": "Cassini",
         "startTime": "1997-10-15 09:26:08.390 UTC",
         "endTime": "2017-09-29 23:58:00.000 UTC",
         "center": "Saturn",
         "trajectory": {
            "type": "Spice",
            "target": "Cassini",
            "center": "Saturn"
         },
         "bodyFrame": {
            "type": "Spice",
            "name": "CASSINI_SC_COORD"
         },
         "geometry": {
            "type": "Mesh",
            "meshRotation": [
               0,
               0,
               -0.70710677,
               0.70710677
            ],
            "size": 0.005,
            "source": "models/cassini/Cassini_no_Huygens_03.3ds"
         },
         "label": {
            "color": [
               0.6,
               1,
               1
            ],
         "fadeSize": 1000000,
         "showText": true
         },
         "trajectoryPlot": {
            "color": [
               0.6,
               1,
               1
            ],
            "lineWidth": 1,
            "duration": "14 d",
            "lead": "3 d",
            "fade": 1,
            "sampleCount": 100
         }
      }
   ]
}
The version and name attributes set the current version of Cosmographia and the internal name of the catalog file.
The class attribute sets the object class to “spacecraft”.
The name attribute sets the name that will be used to identify the spacecraft object within Cosmographia.
The startTime and endTime attributes set the spacecraft “lifetime” span within Cosmographia. These times are optional. For on-going missions either endTime or both startTime and endTime can be omitted. If these items are present, for SPICE-based spacecraft they can be set to the start and stop times of the period for which the spacecraft trajectory and orientation data are available in the SPICE kernels listed in the catalog file defining the mission’s SPICE data.
The center attribute contains the Cosmographia name for the center of the spacecraft’s trajectory plot. This parameter will often be set to “Sun” or the Cosmographia name of the body that the spacecraft orbits.
The trajectory property defines how Cosmographia computes the spacecraft trajectory. The example above tells the program to compute trajectory of CASSINI relative to Saturn using SPICE. In addition to SPICE-based trajectories, Cosmographia supports a few other types of trajectories described in the Trajectory Types  section of this User’s Guide.
The bodyFrame property defines how Cosmographia computes the orientation of the spacecraft’s body-fixed frame. This can be done in two ways – in one step, using just the bodyFrame property (more common, as is done using SPICE data to compute orientation of the CASSINI_SC_COORD frame in the example above), or in two steps, using a combination of the bodyFrame and rotationModel properties. The one-step way defines the orientation of the body-fixed frame with respect to the ICRF frame using one of the supported bodyFrame types described in the Body Frame/Intermediate Frame Types section of this User’s Guide. The two-step way uses the rotationModel property in addition to the bodyFrame property to define the orientation of the body-fixed frame – first rotate from the ICRF frame to an intermediate frame as specified by the bodyFrame property, and second rotate from the intermediate frame to the body-fixed frame as specified by the rotationModel property, using one the supported rotationModel types described in the Rotation Model Types section of this User’s Guide. When the two-step way is used, the property name bodyFrame should be changed to the property name intermediateFrame in the catalog files, solely for clarifying purposes.
For a spacecraft that changes its center of motion, trajectory type, or rotation model the arcs property can be used to specify different properties over different spans of time. For example in the case of CASSINI the arcs property shown below can be used instead of the startTime, endTime, center, trajectory, and bodyFrame properties shown above to define different centers for the cruise and orbital phases:
         "startTime": "1997-10-15 09:26:08.390 UTC",
         "arcs": [
            {
               "endTime": "2004-07-04 02:48:00.000 UTC",
               "center": "Sun",
               "trajectory": {
                  "type": "Spice",
                  "target": "Cassini",
                  "center": "Sun"
               },
               "bodyFrame": {
                  "type": "Spice",
                  "name": "CASSINI_SC_COORD"
               }
            },
            {
               "center": "Saturn",
               "trajectory": {
                  "type": "Spice",
                  "target": "Cassini",
                  "center": "Saturn"
               },
               "bodyFrame": {
                  "type": "Spice",
                  "name": "CASSINI_SC_COORD"
               }
            }
         ],
The geometry property defines the shape that will be used to visualize  the spacecraft. The example above tells the program to use the 3D model (“type”: “Mesh”) provided in the 3DS file specified by the source attribute, to rotate this model to align it with the body-fixed frame using the SPICE-style quaternion given in the meshRotation attribute, and to scale the model to fit a sphere with radius specified by the size attribute. More details about Mesh and other geometry types are provided in the Geometry Types section of this User’s Guide.
The label property defines the appearance of the spacecraft name label shown on the screen. The example above tells the program to use a certain RGB color set by the color attribute, to have the label fade when the spacecraft is at a certain distance from the observer set by the fadeSize attribute, and to always show the label when closer than that distance as set by the showText attribute.
The trajectoryPlot property defines the appearance of the spacecraft trajectory line shown on the screen. The example above tells the program to use a certain RGB color set by the color attribute, to use the line width set by the lineWidth attribute, to plot the trajectory over the time period given by the duration attribute with the lead time given by the lead attribute, to have the trajectory “tail” fade according to the fade factor given in the fade attribute, and to base the trajectory plot on the number  of samples set by the sampleCount attribute.
A more detailed description of some of the parameters in this catalog file is provided in the “CATALOG FILE DEFINING A SPACECRAFT” section of the Cosmographia-SPICE User’s Guide.