Orbital Decay Calculator
Orbital Decay Calculator computes the approximate time for a satellite in low Earth orbit to decay due to atmospheric drag. Input the satellite’s mass, cross-sectional area, drag coefficient, initial orbital altitude, atmospheric scale height, select units, and calculate the orbital lifetime.
Enter Parameters
How to Use Orbital Decay Calculator:
- Enter the satellite’s mass (m), cross-sectional area (A), drag coefficient (C_D, default 2.2), orbital altitude (h), and atmospheric scale height (H, default 8 km) using the keypad or direct input; use “Next” to switch fields.
- Select appropriate units for mass (kg, g), area (m², cm²), altitude (km, m), and scale height (km, m). Drag coefficient is dimensionless.
- Click “Calculate” to see step-by-step results for the orbital lifetime.
- Use “Share Result” to get shareable text or “Copy Result” to copy to clipboard.
Formula:
Orbital Lifetime (T):
T ≈ (2π × a × ρ₀ × H) / (C_D × A / m × v)
Where: T = orbital lifetime (s), a = semi-major axis (m, a = R_E + h), ρ₀ = atmospheric density (kg/m³), H = scale height (m), C_D = drag coefficient, A = cross-sectional area (m²), m = mass (kg), v = orbital velocity (m/s, v = √(GM/a))
Atmospheric Density (ρ₀):
ρ₀ = ρ_ref × exp(-(a – a_ref) / H)
Where: ρ_ref = 1.2×10⁻⁷ kg/m³ at a_ref = 200 km
Important Notes:
- Inputs for mass, area, drag coefficient, altitude, and scale height must be positive. Altitude should be at least 100 km for LEO relevance.
- The calculator assumes a circular orbit and uses a simplified exponential atmosphere model. Actual decay times vary due to atmospheric variations, solar activity, and orbit eccentricity.
- Earth’s radius (R_E = 6,371 km) and gravitational parameter (GM = 3.986×10¹⁴ m³/s²) are used for calculations.
- Results are approximate and best suited for LEO (100-1000 km). For precise modeling, use numerical integration tools.
- Clipboard access requires a secure context (HTTPS). If copying fails, try accessing over HTTPS or copy manually.