Attitude and rotation

Attitude laws

Law	Body frame
Nadir — N/S array axis (GEO-like)	+Z toward the Earth, +Y toward the south celestial pole; with a known orbit, +Y opposite the orbit normal (LVLH)
Nadir — yaw steering	+Z toward the Earth, +Y kept perpendicular to the Sun so the arrays can face it exactly
Sun pointing	+X toward the Sun, +Z as close to nadir as possible
Inertial	Axes of the equatorial frame
Attitude ephemeris (CCSDS AEM)	Quaternions of a loaded AEM file, interpolated

Then the Euler angles apply (yaw about Z, pitch about Y, roll about X), then the rotation, then the array angle.

Solar arrays

With Sun-tracking arrays, the arrays turn about +Y so that their normal is as close to the Sun as possible; the offset adds an angle. Without tracking, the slider sets the array angle.

Rotation

Turn on Put the satellite in rotation:

Mode	Behaviour
Fixed axis	Uniform rotation of period P about an axis fixed in the body (X, Y, Z or any direction)
Free tumbling	Torque-free motion (Euler’s equations) from an initial axis and period: when the axis is not a principal axis, it precesses and nutates

For free tumbling, set the three principal moments of inertia (relative), or estimate them from the bounding box of the model. The animation runs in real time at ×¼, ×1 or ×10.

Attitude ephemeris (AEM)

Load an attitude (AEM) reads a CCSDS Attitude Ephemeris Message with QUATERNION data and switches the law to it. The body axes of the file are taken as those of the model; the Euler angles correct a different convention. Export the attitude writes the current attitude over ±1 hour with a 10 s step. See CCSDS formats.