data rotations

The rotation object defines the rotation axis and rotation (or the absence of rotation) of the body around this axis. Currently only fixed rotation and uniform rotations are supported.

Fixed rotation

A fixed orbit is used to orient a body relative to the reference frame, this is mainly used to orient non rotating bodies.

Parameters

• type: fixed
• axis: Direction of the rotation axis, three components vector, optional, default value is the up vector (0, 0, 1).
• angle: Rotation angle around the defined axis in degrees, mandatory.
• frame: Reference frame of the orientation axis, default value is J2000Equatorial.

Example

    rotation:
        type: fixed
        axis: [0.4372, -0.7548, -0.4891]
        angle: 99.6995

Uniform rotation

Parameters

• type: uniform
• synchronous: true if the rotation is synchronous (tidally locked) with the parent of the body, optional, the default value is false.
• period: Rotation period, mandatory, unless radial speed or synchronous is specified.
• period-units: Period units, optional, the default value is Year.
• ra: Rotation axis right ascension, optional unless inclination is not specified, default is 0.
• ra-units: Right ascension units, optional, the default value is Deg.
• de: Rotation axis declination, optional, default is 0.
• de-units: Declination units, optional, the default value is Deg.
• inclination: Rotation plane inclination, optional, ignored if right ascension is specified, default is 0.
• inclination-units: Inclination units, optional, the default value is Deg.
• ascending-node: Rotation ascending node, optional, ignored if right ascension is specified, default is 0.
• ascending-node-units: Ascending node units, optional, the default value is Deg.
• meridian: Rotation prime meridian angle, optional, default is 0.
• meridian-units: Meridian units, optional, the default value is Deg.
• epoch: Epoch of the rotation parameters, optional, default is J2000.0.
• frame: Reference frame of the rotation, optional, default is J2000Ecliptic.

Example

spacecraft:
    name: ISS
    rotation:
        type: uniform
        synchronous: true
        inclination: 51.6394
        ascending-node: 307.6103
        frame: mean-quatorial

Named rotation

A rotation object can be defined elsewhere and referenced using its name. If more than one rotation object share the same name, the priority of the associated category will be used to select the rotation object.

Parameters

• name: Name of the rotation object, mandatory.
• type: Actual rotation type, e.g. uniform, mandatory
• category: Category of the rotation object, mandatory.

The actual parameters related to the rotation type are added in the object.

Example

- rotation:
    name: unknown-synchronous
    category: uniform
    type: uniform
    synchronous: true
    frame: mean-equatorial