Orbit Propagator (Keplerian)
Two-body Keplerian orbit parameters for quick mission concept trades. Computes period, velocity, ground track velocity, eclipse duration, and J₂ effects.
Orbital elements
Orbit characteristics
Want high-fidelity propagation, ground station passes, or conjunction screening?
Sign up →Frequently asked questions
What's a two-body / Keplerian orbit?
A pure two-body orbit ignores Earth oblateness, atmospheric drag, solar radiation pressure, and third-body perturbations. It's accurate enough for mission concept trades but diverges from reality within days to weeks, especially in LEO.
What is beta angle and how does it affect eclipse?
Beta is the angle between the orbit plane and the Sun vector. At beta = 0° the spacecraft passes directly through Earth's shadow each orbit (maximum eclipse). At higher |beta| the orbit skims the terminator and eclipse time shrinks, reaching zero at the "full-sun" beta.
How is J₂ RAAN drift computed?
The secular rate of right ascension is Ω̇ = −(3/2)·n·J₂·(R_e/p)²·cos(i), where p is the semi-latus rectum, n is mean motion, and J₂ ≈ 1.0826·10⁻³ for Earth. Sun-synchronous orbits match this drift to Earth's mean motion around the Sun (0.9856°/day).
When should I upgrade to a real propagator?
Any time you need atmospheric drag (LEO decay), lunar/solar perturbations (MEO and higher), SRP (large solar arrays), or precise ground-track timing. The Aerospace Pack includes NRLMSISE-00 atmospheric drag, Sun/Moon third-body, and SRP force-model components.
Upgrade for flight-grade orbit analysis
- Full-force-model high-fidelity propagator (RK4, configurable)
- NRLMSISE-00 atmospheric drag with F10.7 / Ap scaling
- Sun/Moon third-body and solar radiation pressure
- Ground-station pass prediction with visibility masks
- Conjunction screening and COLA maneuver planning
- Cislunar / CR3BP design studio for Lagrange-point missions