☀️ Sun-Synchronous Orbit Designer

Required inclination vs altitude · nodal precession · period · ground-track shift

Ad placeholder

Inputs

Results

SSO inclination
– deg
Nodal precession
– °/day
Orbital period
– min
Nodal period
– min
Mean motion
– rev/day
Ground-track shift / rev
– deg
Equator spacing / rev
– km

SSO Inclination vs Altitude

Ad placeholder

📖 How to use

  1. Enter the circular altitude (and eccentricity if slightly elliptical) — the tool solves the inclination that makes the node precess at the sun rate, +0.9856°/day.输入圆轨道高度（若略椭圆可填偏心率）——工具求解使升交点以太阳速率 +0.9856°/天 进动的倾角。
  2. Read the SSO inclination (always retrograde, > 90°), the period and the ground-track shift per rev.读取 SSO 倾角（逆行轨道，恒 > 90°）、周期与每圈地面轨迹西移量。
  3. Pick a local time at the node (LTAN/LTDN) for lighting: 10:30 for optical imaging, 06:00 dawn-dusk for radar/power — the LTAN itself does not change the geometry computed here.按光照选择降交点/升交点地方时（LTAN/LTDN）：光学成像常用 10:30，雷达/供电常用 06:00 晨昏轨道——LTAN 不影响本页几何结果。
  4. Continue in Repeat Ground Track to pick an altitude with an exact revisit cycle, and in Beta Angle & Eclipse to check lighting over the year.接着用回归轨道工具选取具有精确回归周期的高度，用β 角与阴影工具检查全年光照。

The sun-synchronous condition

J2 (Earth oblateness) makes the ascending node precess at

Ω̇ = −(3/2)·J₂·n·(R_E/p)²·cos i

A sun-synchronous orbit chooses i so that Ω̇ equals the mean sun rate, 360°/365.2422 d = +0.9856°/day. The orbit plane then keeps a fixed orientation to the sun, so every pass sees the ground at the same local solar time — ideal for optical Earth observation (consistent shadows) and for dawn-dusk power/thermal design.

Solving for inclination: cos i = −Ω̇_sun / ((3/2)·J₂·n·(R_E/p)²). Because cos i must be negative, SSO is always retrograde (i ≈ 96–99° for LEO). Above ≈ 5 970 km altitude no solution exists.

All computation runs locally in your browser.

太阳同步条件

地球扁率(J2)使升交点以下式进动：

Ω̇ = −(3/2)·J₂·n·(R_E/p)²·cos i

太阳同步轨道选择倾角 i，使 Ω̇ 等于平太阳速率 360°/365.2422 天 = +0.9856°/天。轨道面相对太阳保持固定取向，每次过境的地方太阳时相同——最适合光学对地观测（光照一致）与晨昏轨道的能源/热设计。

解倾角：cos i = −Ω̇_sun / ((3/2)·J₂·n·(R_E/p)²)。因 cos i 必须为负，SSO 恒为逆行轨道（LEO 约 96–99°）。高度超过约 5 970 km 无解。

全部计算在你的浏览器本地完成。