Beta Angle Calculator

What It Does

The Beta Angle Calculator returns the angle between the sun vector and the orbit plane for any orbit and date. Input inclination, RAAN, and date (or epoch), and the calculator returns the beta angle in degrees. It plots beta angle over the mission lifetime so you can see the seasonal envelope and identify the worst-case hot and cold cases for thermal design. Supports both Earth-orbiting and Sun-orbiting spacecraft.

Key Features

• Beta angle from orbit elements and date (closed-form, no propagator needed)
• Annual beta angle envelope plot with hot and cold case extremes
• Eclipse-vs-full-sun threshold detection (the |β| ≈ 70° transition)
• Earth orbit and heliocentric orbit support

Why It Matters

Beta angle is the master variable for spacecraft thermal design and power profile. At |β| < ~70° the spacecraft sees regular eclipses; above that the orbit becomes "full sun" and eclipses disappear, which sounds great for power but is brutal for thermal because the radiator has nowhere to dump heat. Every Earth-observing satellite has a beta angle envelope; ignoring it leads to overheating in summer or battery brownout in winter. The calculator surfaces the seasonal extremes early so the thermal team can size radiators against the right worst case.

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