Orbits & Satellites

Periapsis and Apoapsis Calculator

Calculate periapsis and apoapsis with explicit astronomical inputs and a visible equation.

Astronomy & Space · Orbits & Satellites

Enter the astronomical quantities

Private in-browser model · explicit units and assumptions

Periapsis and ApoapsisPeriapsis = a(1−e); apoapsis = a(1+e)

1EnterProvide the known values
2CalculateResults update automatically
3VerifyReview the details and units

Try an example

Semi-major axis (km)

Eccentricity ()

Periapsis and Apoapsis result

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Understand the astronomy model

What this calculator explains

Calculate periapsis and apoapsis with explicit astronomical inputs and a visible equation. The schematic comes before the examples and inputs so the geometry and measured quantities remain easy to identify.

Governing relationship

Periapsis = a(1−e); apoapsis = a(1+e)

Model boundary

This idealized relationship does not supply live ephemerides, weather, visibility, equipment approval, mission navigation or safety decisions.

Quick guide

How to use this calculator

Choose the complete example closest to your situation.
Replace the example with measurements in the displayed units.
Check the equation and model boundary before interpreting the result.

Calculation method

Transparent astronomy calculation

Periapsis = a(1−e); apoapsis = a(1+e)

No hidden catalog, weather, ephemeris or equipment preset is introduced.

Worked example

Three complete starting scenarios

Load the complete low orbit scenario.

Periapsis = a(1−e); apoapsis = a(1+e)

Supported inputs

Precision and limits

Idealized calculation

This idealized relationship does not supply live ephemerides, weather, visibility, equipment approval, mission navigation or safety decisions.

Coordinates and epochs

When coordinates or time are involved, keep the same epoch, longitude convention and reference frame.

Not a live sky forecast

The calculator does not know cloud, seeing, transparency, obstructions or current equipment condition.

Privacy

Entered astronomy values remain in this browser.