Reference Frames

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Reference Frames are ordered sets of three orthogonal direction vectors labeled X, Y, and Z. Block 2 of the object context menu provides options enabling users to visualize different types of reference frames. Some of these frames are related to the selected object while other are related other objects or to solar system in general. Independently of that all frames picked from object’s context menu are shown centered at that object. Once visualized, frame axes are treated as individual vectors, allowing any Vector functions to be used on them.

There are a total of four types of frames that can be visualized:

Frame	Description	Method(s) to Render Frame
ICRF	Shows International Celestial Reference Frame (ICRF), the core inertial reference frame in which Cosmographia computes all positions and orientations.	Object Menu: Right-click object and click ICRF from the displayed options. This does not work for sensors and observations.
Intermediate Frame	Shows the intermediate frame used in defining the object’s orientation in the case of a two-step rotation definition.	Object Menu: Right-click object and click Intermediate Frame from the displayed options. This does not work for sensors and observations
Body Fixed Frame	Shows the body-fixed frame, which is the frame that fixed to and rotates with the object.	Object Menu: Right-click object and click Body Fixed Frame from the displayed options. This does not work for sensors and observations
Spice Frames	Opens a list of all SPICE frames built into the SPICE toolkit and defined in all frames kernels loaded into Cosmographia at the moment from which one or more SPICE frames can be picked for visualization. As the other three types of frames, SPICE frames are shown centered at the selected body independently of the actual centers defined for these frames in SPICE system.	Object Menu: Right-click object and click Spice Frames from the displayed options. Click on desired frame to show it on body. This does not work for sensors and observations.

If the object’s body-fixed frame orientation is defined in one step (from the ICRF frame to the body-fixed frame), Block 2 of the object context menu will include only three options — ‘ICRF’, ‘Body-fixed frame’, and ‘SPICE Frame’.

If the object’s body-fixed frame orientation is defined in two steps (from the ICRF frame to an intermediate frame and from the intermediate frame to the body-fixed frame), Block 2 of the object context menu will include the ‘Intermediate Frame’ option for showing this intermediate frame in addition to the ‘ICRF’, ‘Body-fixed frame’, and ‘SPICE Frame’ options.

The axes of ICRF and Intermediate Frame are shown semi-transparent while the axes of the Body Fixed Frame and Spice Frames are shown in solid color. The transparency level as well as the color, label text, and size of any displayed frame axis can be changed by right-clicking the axis and clicking Set Properties.

Note that if no SPICE kernels were loaded into Cosmograpia — as for example when SPICE Driven Bodies are turned off — or if loaded SPICE kernels do not provide orientation data for the chosen SPICE frame, this SPICE frame will be displayed co-aligned with ICRF.