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###### tags: `CubeSat` `Satellite` `quaternion orientation`
---
# Orientation of Satellite and Y-axis spin
>[color=red]**X** is the line tangential to the forward motion of the spacecraft.
>**Z** is the radial line pointing toward the center of the Earth.
>**Y** is the line 90° to the other two axes

∆以上可作為四元數計算時的座標軸
## Formosat-8
|特性|數值|
|-|-|
|飛行高度|500 ~ 600km|
|飛行速度|7500m/s|
∆ 可用Google Earth 模擬
## Y-axis Spin
The y-axis spin rate is chosen such that, when a boom is deployed along the z-axis in a later phase, the y-axis spin rate coincides with the angular change of the spacecraft in orbit about the Earth. In a nearly circular orbit, this conveniently fixes the spacecraft body axes to the orbit tangent-normal-radial (TNR) reference frame. If deployed with the boom pointing to nadir, the gravity gradient restoring forces stabilize the system as well.

∆ 衛星發射時可能會頭尾翻轉滾動