Orbital Period Calculator (Kepler's Third Law)

What It Does

The Orbital Period Calculator applies Kepler's third law (T = 2π × √(a³/μ)) to compute the orbital period of any spacecraft from its semi-major axis. Enter altitude (for circular orbits) or semi-major axis (for elliptical) and the calculator returns the period in seconds, minutes, hours, and revolutions per day. Built-in central body presets cover Earth, Moon, Mars, Venus, Sun, and Jupiter, with a custom μ field for asteroid and small-body missions.

Key Features

• Computes period from altitude (circular) or semi-major axis (elliptical)
• Output in seconds, minutes, hours, and revolutions per sidereal day
• Central body presets for Earth, Moon, Mars, Venus, Sun, Jupiter
• Custom gravitational parameter input for small bodies and asteroids

Why It Matters

Orbital period drives almost everything downstream of orbit selection: revisit time over a target, ground station contact frequency, eclipse cadence, thermal cycling rate, and battery cycle life. A LEO mission at 400 km has 90-minute periods and 16 revs/day; one at 800 km has 100-minute periods and 14 revs/day. That difference cascades into ConOps, downlink scheduling, and even battery sizing. Getting the period right at concept stage anchors the rest of the mission timeline.

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